Merge remote-tracking branch 'asoc/fix/intel' into asoc-linus

[mirror_ubuntu-bionic-kernel.git] / drivers / tty / serial / amba-pl011.c

// SPDX-License-Identifier: GPL-2.0+
/*
 *  Driver for AMBA serial ports
 *
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *
 *  Copyright 1999 ARM Limited
 *  Copyright (C) 2000 Deep Blue Solutions Ltd.
 *  Copyright (C) 2010 ST-Ericsson SA
 *
 * This is a generic driver for ARM AMBA-type serial ports.  They
 * have a lot of 16550-like features, but are not register compatible.
 * Note that although they do have CTS, DCD and DSR inputs, they do
 * not have an RI input, nor do they have DTR or RTS outputs.  If
 * required, these have to be supplied via some other means (eg, GPIO)
 * and hooked into this driver.
 */


#if defined(CONFIG_SERIAL_AMBA_PL011_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/module.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/amba/bus.h>
#include <linux/amba/serial.h>
#include <linux/clk.h>
#include <linux/slab.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/scatterlist.h>
#include <linux/delay.h>
#include <linux/types.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/pinctrl/consumer.h>
#include <linux/sizes.h>
#include <linux/io.h>
#include <linux/acpi.h>

#include "amba-pl011.h"

#define UART_NR                 14

#define SERIAL_AMBA_MAJOR       204
#define SERIAL_AMBA_MINOR       64
#define SERIAL_AMBA_NR          UART_NR

#define AMBA_ISR_PASS_LIMIT     256

#define UART_DR_ERROR           (UART011_DR_OE|UART011_DR_BE|UART011_DR_PE|UART011_DR_FE)
#define UART_DUMMY_DR_RX        (1 << 16)

static u16 pl011_std_offsets[REG_ARRAY_SIZE] = {
        [REG_DR] = UART01x_DR,
        [REG_FR] = UART01x_FR,
        [REG_LCRH_RX] = UART011_LCRH,
        [REG_LCRH_TX] = UART011_LCRH,
        [REG_IBRD] = UART011_IBRD,
        [REG_FBRD] = UART011_FBRD,
        [REG_CR] = UART011_CR,
        [REG_IFLS] = UART011_IFLS,
        [REG_IMSC] = UART011_IMSC,
        [REG_RIS] = UART011_RIS,
        [REG_MIS] = UART011_MIS,
        [REG_ICR] = UART011_ICR,
        [REG_DMACR] = UART011_DMACR,
};

/* There is by now at least one vendor with differing details, so handle it */
struct vendor_data {
        const u16               *reg_offset;
        unsigned int            ifls;
        unsigned int            fr_busy;
        unsigned int            fr_dsr;
        unsigned int            fr_cts;
        unsigned int            fr_ri;
        unsigned int            inv_fr;
        bool                    access_32b;
        bool                    oversampling;
        bool                    dma_threshold;
        bool                    cts_event_workaround;
        bool                    always_enabled;
        bool                    fixed_options;

        unsigned int (*get_fifosize)(struct amba_device *dev);
};

static unsigned int get_fifosize_arm(struct amba_device *dev)
{
        return amba_rev(dev) < 3 ? 16 : 32;
}

static struct vendor_data vendor_arm = {
        .reg_offset             = pl011_std_offsets,
        .ifls                   = UART011_IFLS_RX4_8|UART011_IFLS_TX4_8,
        .fr_busy                = UART01x_FR_BUSY,
        .fr_dsr                 = UART01x_FR_DSR,
        .fr_cts                 = UART01x_FR_CTS,
        .fr_ri                  = UART011_FR_RI,
        .oversampling           = false,
        .dma_threshold          = false,
        .cts_event_workaround   = false,
        .always_enabled         = false,
        .fixed_options          = false,
        .get_fifosize           = get_fifosize_arm,
};

static const struct vendor_data vendor_sbsa = {
        .reg_offset             = pl011_std_offsets,
        .fr_busy                = UART01x_FR_BUSY,
        .fr_dsr                 = UART01x_FR_DSR,
        .fr_cts                 = UART01x_FR_CTS,
        .fr_ri                  = UART011_FR_RI,
        .access_32b             = true,
        .oversampling           = false,
        .dma_threshold          = false,
        .cts_event_workaround   = false,
        .always_enabled         = true,
        .fixed_options          = true,
};

#ifdef CONFIG_ACPI_SPCR_TABLE
static const struct vendor_data vendor_qdt_qdf2400_e44 = {
        .reg_offset             = pl011_std_offsets,
        .fr_busy                = UART011_FR_TXFE,
        .fr_dsr                 = UART01x_FR_DSR,
        .fr_cts                 = UART01x_FR_CTS,
        .fr_ri                  = UART011_FR_RI,
        .inv_fr                 = UART011_FR_TXFE,
        .access_32b             = true,
        .oversampling           = false,
        .dma_threshold          = false,
        .cts_event_workaround   = false,
        .always_enabled         = true,
        .fixed_options          = true,
};
#endif

static u16 pl011_st_offsets[REG_ARRAY_SIZE] = {
        [REG_DR] = UART01x_DR,
        [REG_ST_DMAWM] = ST_UART011_DMAWM,
        [REG_ST_TIMEOUT] = ST_UART011_TIMEOUT,
        [REG_FR] = UART01x_FR,
        [REG_LCRH_RX] = ST_UART011_LCRH_RX,
        [REG_LCRH_TX] = ST_UART011_LCRH_TX,
        [REG_IBRD] = UART011_IBRD,
        [REG_FBRD] = UART011_FBRD,
        [REG_CR] = UART011_CR,
        [REG_IFLS] = UART011_IFLS,
        [REG_IMSC] = UART011_IMSC,
        [REG_RIS] = UART011_RIS,
        [REG_MIS] = UART011_MIS,
        [REG_ICR] = UART011_ICR,
        [REG_DMACR] = UART011_DMACR,
        [REG_ST_XFCR] = ST_UART011_XFCR,
        [REG_ST_XON1] = ST_UART011_XON1,
        [REG_ST_XON2] = ST_UART011_XON2,
        [REG_ST_XOFF1] = ST_UART011_XOFF1,
        [REG_ST_XOFF2] = ST_UART011_XOFF2,
        [REG_ST_ITCR] = ST_UART011_ITCR,
        [REG_ST_ITIP] = ST_UART011_ITIP,
        [REG_ST_ABCR] = ST_UART011_ABCR,
        [REG_ST_ABIMSC] = ST_UART011_ABIMSC,
};

static unsigned int get_fifosize_st(struct amba_device *dev)
{
        return 64;
}

static struct vendor_data vendor_st = {
        .reg_offset             = pl011_st_offsets,
        .ifls                   = UART011_IFLS_RX_HALF|UART011_IFLS_TX_HALF,
        .fr_busy                = UART01x_FR_BUSY,
        .fr_dsr                 = UART01x_FR_DSR,
        .fr_cts                 = UART01x_FR_CTS,
        .fr_ri                  = UART011_FR_RI,
        .oversampling           = true,
        .dma_threshold          = true,
        .cts_event_workaround   = true,
        .always_enabled         = false,
        .fixed_options          = false,
        .get_fifosize           = get_fifosize_st,
};

static const u16 pl011_zte_offsets[REG_ARRAY_SIZE] = {
        [REG_DR] = ZX_UART011_DR,
        [REG_FR] = ZX_UART011_FR,
        [REG_LCRH_RX] = ZX_UART011_LCRH,
        [REG_LCRH_TX] = ZX_UART011_LCRH,
        [REG_IBRD] = ZX_UART011_IBRD,
        [REG_FBRD] = ZX_UART011_FBRD,
        [REG_CR] = ZX_UART011_CR,
        [REG_IFLS] = ZX_UART011_IFLS,
        [REG_IMSC] = ZX_UART011_IMSC,
        [REG_RIS] = ZX_UART011_RIS,
        [REG_MIS] = ZX_UART011_MIS,
        [REG_ICR] = ZX_UART011_ICR,
        [REG_DMACR] = ZX_UART011_DMACR,
};

static unsigned int get_fifosize_zte(struct amba_device *dev)
{
        return 16;
}

static struct vendor_data vendor_zte = {
        .reg_offset             = pl011_zte_offsets,
        .access_32b             = true,
        .ifls                   = UART011_IFLS_RX4_8|UART011_IFLS_TX4_8,
        .fr_busy                = ZX_UART01x_FR_BUSY,
        .fr_dsr                 = ZX_UART01x_FR_DSR,
        .fr_cts                 = ZX_UART01x_FR_CTS,
        .fr_ri                  = ZX_UART011_FR_RI,
        .get_fifosize           = get_fifosize_zte,
};

/* Deals with DMA transactions */

struct pl011_sgbuf {
        struct scatterlist sg;
        char *buf;
};

struct pl011_dmarx_data {
        struct dma_chan         *chan;
        struct completion       complete;
        bool                    use_buf_b;
        struct pl011_sgbuf      sgbuf_a;
        struct pl011_sgbuf      sgbuf_b;
        dma_cookie_t            cookie;
        bool                    running;
        struct timer_list       timer;
        unsigned int last_residue;
        unsigned long last_jiffies;
        bool auto_poll_rate;
        unsigned int poll_rate;
        unsigned int poll_timeout;
};

struct pl011_dmatx_data {
        struct dma_chan         *chan;
        struct scatterlist      sg;
        char                    *buf;
        bool                    queued;
};

/*
 * We wrap our port structure around the generic uart_port.
 */
struct uart_amba_port {
        struct uart_port        port;
        const u16               *reg_offset;
        struct clk              *clk;
        const struct vendor_data *vendor;
        unsigned int            dmacr;          /* dma control reg */
        unsigned int            im;             /* interrupt mask */
        unsigned int            old_status;
        unsigned int            fifosize;       /* vendor-specific */
        unsigned int            old_cr;         /* state during shutdown */
        unsigned int            fixed_baud;     /* vendor-set fixed baud rate */
        char                    type[12];
#ifdef CONFIG_DMA_ENGINE
        /* DMA stuff */
        bool                    using_tx_dma;
        bool                    using_rx_dma;
        struct pl011_dmarx_data dmarx;
        struct pl011_dmatx_data dmatx;
        bool                    dma_probed;
#endif
};

static unsigned int pl011_reg_to_offset(const struct uart_amba_port *uap,
        unsigned int reg)
{
        return uap->reg_offset[reg];
}

static unsigned int pl011_read(const struct uart_amba_port *uap,
        unsigned int reg)
{
        void __iomem *addr = uap->port.membase + pl011_reg_to_offset(uap, reg);

        return (uap->port.iotype == UPIO_MEM32) ?
                readl_relaxed(addr) : readw_relaxed(addr);
}

static void pl011_write(unsigned int val, const struct uart_amba_port *uap,
        unsigned int reg)
{
        void __iomem *addr = uap->port.membase + pl011_reg_to_offset(uap, reg);

        if (uap->port.iotype == UPIO_MEM32)
                writel_relaxed(val, addr);
        else
                writew_relaxed(val, addr);
}

/*
 * Reads up to 256 characters from the FIFO or until it's empty and
 * inserts them into the TTY layer. Returns the number of characters
 * read from the FIFO.
 */
static int pl011_fifo_to_tty(struct uart_amba_port *uap)
{
        u16 status;
        unsigned int ch, flag, max_count = 256;
        int fifotaken = 0;

        while (max_count--) {
                status = pl011_read(uap, REG_FR);
                if (status & UART01x_FR_RXFE)
                        break;

                /* Take chars from the FIFO and update status */
                ch = pl011_read(uap, REG_DR) | UART_DUMMY_DR_RX;
                flag = TTY_NORMAL;
                uap->port.icount.rx++;
                fifotaken++;

                if (unlikely(ch & UART_DR_ERROR)) {
                        if (ch & UART011_DR_BE) {
                                ch &= ~(UART011_DR_FE | UART011_DR_PE);
                                uap->port.icount.brk++;
                                if (uart_handle_break(&uap->port))
                                        continue;
                        } else if (ch & UART011_DR_PE)
                                uap->port.icount.parity++;
                        else if (ch & UART011_DR_FE)
                                uap->port.icount.frame++;
                        if (ch & UART011_DR_OE)
                                uap->port.icount.overrun++;

                        ch &= uap->port.read_status_mask;

                        if (ch & UART011_DR_BE)
                                flag = TTY_BREAK;
                        else if (ch & UART011_DR_PE)
                                flag = TTY_PARITY;
                        else if (ch & UART011_DR_FE)
                                flag = TTY_FRAME;
                }

                if (uart_handle_sysrq_char(&uap->port, ch & 255))
                        continue;

                uart_insert_char(&uap->port, ch, UART011_DR_OE, ch, flag);
        }

        return fifotaken;
}


/*
 * All the DMA operation mode stuff goes inside this ifdef.
 * This assumes that you have a generic DMA device interface,
 * no custom DMA interfaces are supported.
 */
#ifdef CONFIG_DMA_ENGINE

#define PL011_DMA_BUFFER_SIZE PAGE_SIZE

static int pl011_sgbuf_init(struct dma_chan *chan, struct pl011_sgbuf *sg,
        enum dma_data_direction dir)
{
        dma_addr_t dma_addr;

        sg->buf = dma_alloc_coherent(chan->device->dev,
                PL011_DMA_BUFFER_SIZE, &dma_addr, GFP_KERNEL);
        if (!sg->buf)
                return -ENOMEM;

        sg_init_table(&sg->sg, 1);
        sg_set_page(&sg->sg, phys_to_page(dma_addr),
                PL011_DMA_BUFFER_SIZE, offset_in_page(dma_addr));
        sg_dma_address(&sg->sg) = dma_addr;
        sg_dma_len(&sg->sg) = PL011_DMA_BUFFER_SIZE;

        return 0;
}

static void pl011_sgbuf_free(struct dma_chan *chan, struct pl011_sgbuf *sg,
        enum dma_data_direction dir)
{
        if (sg->buf) {
                dma_free_coherent(chan->device->dev,
                        PL011_DMA_BUFFER_SIZE, sg->buf,
                        sg_dma_address(&sg->sg));
        }
}

static void pl011_dma_probe(struct uart_amba_port *uap)
{
        /* DMA is the sole user of the platform data right now */
        struct amba_pl011_data *plat = dev_get_platdata(uap->port.dev);
        struct device *dev = uap->port.dev;
        struct dma_slave_config tx_conf = {
                .dst_addr = uap->port.mapbase +
                                 pl011_reg_to_offset(uap, REG_DR),
                .dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
                .direction = DMA_MEM_TO_DEV,
                .dst_maxburst = uap->fifosize >> 1,
                .device_fc = false,
        };
        struct dma_chan *chan;
        dma_cap_mask_t mask;

        uap->dma_probed = true;
        chan = dma_request_slave_channel_reason(dev, "tx");
        if (IS_ERR(chan)) {
                if (PTR_ERR(chan) == -EPROBE_DEFER) {
                        uap->dma_probed = false;
                        return;
                }

                /* We need platform data */
                if (!plat || !plat->dma_filter) {
                        dev_info(uap->port.dev, "no DMA platform data\n");
                        return;
                }

                /* Try to acquire a generic DMA engine slave TX channel */
                dma_cap_zero(mask);
                dma_cap_set(DMA_SLAVE, mask);

                chan = dma_request_channel(mask, plat->dma_filter,
                                                plat->dma_tx_param);
                if (!chan) {
                        dev_err(uap->port.dev, "no TX DMA channel!\n");
                        return;
                }
        }

        dmaengine_slave_config(chan, &tx_conf);
        uap->dmatx.chan = chan;

        dev_info(uap->port.dev, "DMA channel TX %s\n",
                 dma_chan_name(uap->dmatx.chan));

        /* Optionally make use of an RX channel as well */
        chan = dma_request_slave_channel(dev, "rx");

        if (!chan && plat && plat->dma_rx_param) {
                chan = dma_request_channel(mask, plat->dma_filter, plat->dma_rx_param);

                if (!chan) {
                        dev_err(uap->port.dev, "no RX DMA channel!\n");
                        return;
                }
        }

        if (chan) {
                struct dma_slave_config rx_conf = {
                        .src_addr = uap->port.mapbase +
                                pl011_reg_to_offset(uap, REG_DR),
                        .src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
                        .direction = DMA_DEV_TO_MEM,
                        .src_maxburst = uap->fifosize >> 2,
                        .device_fc = false,
                };
                struct dma_slave_caps caps;

                /*
                 * Some DMA controllers provide information on their capabilities.
                 * If the controller does, check for suitable residue processing
                 * otherwise assime all is well.
                 */
                if (0 == dma_get_slave_caps(chan, &caps)) {
                        if (caps.residue_granularity ==
                                        DMA_RESIDUE_GRANULARITY_DESCRIPTOR) {
                                dma_release_channel(chan);
                                dev_info(uap->port.dev,
                                        "RX DMA disabled - no residue processing\n");
                                return;
                        }
                }
                dmaengine_slave_config(chan, &rx_conf);
                uap->dmarx.chan = chan;

                uap->dmarx.auto_poll_rate = false;
                if (plat && plat->dma_rx_poll_enable) {
                        /* Set poll rate if specified. */
                        if (plat->dma_rx_poll_rate) {
                                uap->dmarx.auto_poll_rate = false;
                                uap->dmarx.poll_rate = plat->dma_rx_poll_rate;
                        } else {
                                /*
                                 * 100 ms defaults to poll rate if not
                                 * specified. This will be adjusted with
                                 * the baud rate at set_termios.
                                 */
                                uap->dmarx.auto_poll_rate = true;
                                uap->dmarx.poll_rate =  100;
                        }
                        /* 3 secs defaults poll_timeout if not specified. */
                        if (plat->dma_rx_poll_timeout)
                                uap->dmarx.poll_timeout =
                                        plat->dma_rx_poll_timeout;
                        else
                                uap->dmarx.poll_timeout = 3000;
                } else if (!plat && dev->of_node) {
                        uap->dmarx.auto_poll_rate = of_property_read_bool(
                                                dev->of_node, "auto-poll");
                        if (uap->dmarx.auto_poll_rate) {
                                u32 x;

                                if (0 == of_property_read_u32(dev->of_node,
                                                "poll-rate-ms", &x))
                                        uap->dmarx.poll_rate = x;
                                else
                                        uap->dmarx.poll_rate = 100;
                                if (0 == of_property_read_u32(dev->of_node,
                                                "poll-timeout-ms", &x))
                                        uap->dmarx.poll_timeout = x;
                                else
                                        uap->dmarx.poll_timeout = 3000;
                        }
                }
                dev_info(uap->port.dev, "DMA channel RX %s\n",
                         dma_chan_name(uap->dmarx.chan));
        }
}

static void pl011_dma_remove(struct uart_amba_port *uap)
{
        if (uap->dmatx.chan)
                dma_release_channel(uap->dmatx.chan);
        if (uap->dmarx.chan)
                dma_release_channel(uap->dmarx.chan);
}

/* Forward declare these for the refill routine */
static int pl011_dma_tx_refill(struct uart_amba_port *uap);
static void pl011_start_tx_pio(struct uart_amba_port *uap);

/*
 * The current DMA TX buffer has been sent.
 * Try to queue up another DMA buffer.
 */
static void pl011_dma_tx_callback(void *data)
{
        struct uart_amba_port *uap = data;
        struct pl011_dmatx_data *dmatx = &uap->dmatx;
        unsigned long flags;
        u16 dmacr;

        spin_lock_irqsave(&uap->port.lock, flags);
        if (uap->dmatx.queued)
                dma_unmap_sg(dmatx->chan->device->dev, &dmatx->sg, 1,
                             DMA_TO_DEVICE);

        dmacr = uap->dmacr;
        uap->dmacr = dmacr & ~UART011_TXDMAE;
        pl011_write(uap->dmacr, uap, REG_DMACR);

        /*
         * If TX DMA was disabled, it means that we've stopped the DMA for
         * some reason (eg, XOFF received, or we want to send an X-char.)
         *
         * Note: we need to be careful here of a potential race between DMA
         * and the rest of the driver - if the driver disables TX DMA while
         * a TX buffer completing, we must update the tx queued status to
         * get further refills (hence we check dmacr).
         */
        if (!(dmacr & UART011_TXDMAE) || uart_tx_stopped(&uap->port) ||
            uart_circ_empty(&uap->port.state->xmit)) {
                uap->dmatx.queued = false;
                spin_unlock_irqrestore(&uap->port.lock, flags);
                return;
        }

        if (pl011_dma_tx_refill(uap) <= 0)
                /*
                 * We didn't queue a DMA buffer for some reason, but we
                 * have data pending to be sent.  Re-enable the TX IRQ.
                 */
                pl011_start_tx_pio(uap);

        spin_unlock_irqrestore(&uap->port.lock, flags);
}

/*
 * Try to refill the TX DMA buffer.
 * Locking: called with port lock held and IRQs disabled.
 * Returns:
 *   1 if we queued up a TX DMA buffer.
 *   0 if we didn't want to handle this by DMA
 *  <0 on error
 */
static int pl011_dma_tx_refill(struct uart_amba_port *uap)
{
        struct pl011_dmatx_data *dmatx = &uap->dmatx;
        struct dma_chan *chan = dmatx->chan;
        struct dma_device *dma_dev = chan->device;
        struct dma_async_tx_descriptor *desc;
        struct circ_buf *xmit = &uap->port.state->xmit;
        unsigned int count;

        /*
         * Try to avoid the overhead involved in using DMA if the
         * transaction fits in the first half of the FIFO, by using
         * the standard interrupt handling.  This ensures that we
         * issue a uart_write_wakeup() at the appropriate time.
         */
        count = uart_circ_chars_pending(xmit);
        if (count < (uap->fifosize >> 1)) {
                uap->dmatx.queued = false;
                return 0;
        }

        /*
         * Bodge: don't send the last character by DMA, as this
         * will prevent XON from notifying us to restart DMA.
         */
        count -= 1;

        /* Else proceed to copy the TX chars to the DMA buffer and fire DMA */
        if (count > PL011_DMA_BUFFER_SIZE)
                count = PL011_DMA_BUFFER_SIZE;

        if (xmit->tail < xmit->head)
                memcpy(&dmatx->buf[0], &xmit->buf[xmit->tail], count);
        else {
                size_t first = UART_XMIT_SIZE - xmit->tail;
                size_t second;

                if (first > count)
                        first = count;
                second = count - first;

                memcpy(&dmatx->buf[0], &xmit->buf[xmit->tail], first);
                if (second)
                        memcpy(&dmatx->buf[first], &xmit->buf[0], second);
        }

        dmatx->sg.length = count;

        if (dma_map_sg(dma_dev->dev, &dmatx->sg, 1, DMA_TO_DEVICE) != 1) {
                uap->dmatx.queued = false;
                dev_dbg(uap->port.dev, "unable to map TX DMA\n");
                return -EBUSY;
        }

        desc = dmaengine_prep_slave_sg(chan, &dmatx->sg, 1, DMA_MEM_TO_DEV,
                                             DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!desc) {
                dma_unmap_sg(dma_dev->dev, &dmatx->sg, 1, DMA_TO_DEVICE);
                uap->dmatx.queued = false;
                /*
                 * If DMA cannot be used right now, we complete this
                 * transaction via IRQ and let the TTY layer retry.
                 */
                dev_dbg(uap->port.dev, "TX DMA busy\n");
                return -EBUSY;
        }

        /* Some data to go along to the callback */
        desc->callback = pl011_dma_tx_callback;
        desc->callback_param = uap;

        /* All errors should happen at prepare time */
        dmaengine_submit(desc);

        /* Fire the DMA transaction */
        dma_dev->device_issue_pending(chan);

        uap->dmacr |= UART011_TXDMAE;
        pl011_write(uap->dmacr, uap, REG_DMACR);
        uap->dmatx.queued = true;

        /*
         * Now we know that DMA will fire, so advance the ring buffer
         * with the stuff we just dispatched.
         */
        xmit->tail = (xmit->tail + count) & (UART_XMIT_SIZE - 1);
        uap->port.icount.tx += count;

        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(&uap->port);

        return 1;
}

/*
 * We received a transmit interrupt without a pending X-char but with
 * pending characters.
 * Locking: called with port lock held and IRQs disabled.
 * Returns:
 *   false if we want to use PIO to transmit
 *   true if we queued a DMA buffer
 */
static bool pl011_dma_tx_irq(struct uart_amba_port *uap)
{
        if (!uap->using_tx_dma)
                return false;

        /*
         * If we already have a TX buffer queued, but received a
         * TX interrupt, it will be because we've just sent an X-char.
         * Ensure the TX DMA is enabled and the TX IRQ is disabled.
         */
        if (uap->dmatx.queued) {
                uap->dmacr |= UART011_TXDMAE;
                pl011_write(uap->dmacr, uap, REG_DMACR);
                uap->im &= ~UART011_TXIM;
                pl011_write(uap->im, uap, REG_IMSC);
                return true;
        }

        /*
         * We don't have a TX buffer queued, so try to queue one.
         * If we successfully queued a buffer, mask the TX IRQ.
         */
        if (pl011_dma_tx_refill(uap) > 0) {
                uap->im &= ~UART011_TXIM;
                pl011_write(uap->im, uap, REG_IMSC);
                return true;
        }
        return false;
}

/*
 * Stop the DMA transmit (eg, due to received XOFF).
 * Locking: called with port lock held and IRQs disabled.
 */
static inline void pl011_dma_tx_stop(struct uart_amba_port *uap)
{
        if (uap->dmatx.queued) {
                uap->dmacr &= ~UART011_TXDMAE;
                pl011_write(uap->dmacr, uap, REG_DMACR);
        }
}

/*
 * Try to start a DMA transmit, or in the case of an XON/OFF
 * character queued for send, try to get that character out ASAP.
 * Locking: called with port lock held and IRQs disabled.
 * Returns:
 *   false if we want the TX IRQ to be enabled
 *   true if we have a buffer queued
 */
static inline bool pl011_dma_tx_start(struct uart_amba_port *uap)
{
        u16 dmacr;

        if (!uap->using_tx_dma)
                return false;

        if (!uap->port.x_char) {
                /* no X-char, try to push chars out in DMA mode */
                bool ret = true;

                if (!uap->dmatx.queued) {
                        if (pl011_dma_tx_refill(uap) > 0) {
                                uap->im &= ~UART011_TXIM;
                                pl011_write(uap->im, uap, REG_IMSC);
                        } else
                                ret = false;
                } else if (!(uap->dmacr & UART011_TXDMAE)) {
                        uap->dmacr |= UART011_TXDMAE;
                        pl011_write(uap->dmacr, uap, REG_DMACR);
                }
                return ret;
        }

        /*
         * We have an X-char to send.  Disable DMA to prevent it loading
         * the TX fifo, and then see if we can stuff it into the FIFO.
         */
        dmacr = uap->dmacr;
        uap->dmacr &= ~UART011_TXDMAE;
        pl011_write(uap->dmacr, uap, REG_DMACR);

        if (pl011_read(uap, REG_FR) & UART01x_FR_TXFF) {
                /*
                 * No space in the FIFO, so enable the transmit interrupt
                 * so we know when there is space.  Note that once we've
                 * loaded the character, we should just re-enable DMA.
                 */
                return false;
        }

        pl011_write(uap->port.x_char, uap, REG_DR);
        uap->port.icount.tx++;
        uap->port.x_char = 0;

        /* Success - restore the DMA state */
        uap->dmacr = dmacr;
        pl011_write(dmacr, uap, REG_DMACR);

        return true;
}

/*
 * Flush the transmit buffer.
 * Locking: called with port lock held and IRQs disabled.
 */
static void pl011_dma_flush_buffer(struct uart_port *port)
__releases(&uap->port.lock)
__acquires(&uap->port.lock)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);

        if (!uap->using_tx_dma)
                return;

        /* Avoid deadlock with the DMA engine callback */
        spin_unlock(&uap->port.lock);
        dmaengine_terminate_all(uap->dmatx.chan);
        spin_lock(&uap->port.lock);
        if (uap->dmatx.queued) {
                dma_unmap_sg(uap->dmatx.chan->device->dev, &uap->dmatx.sg, 1,
                             DMA_TO_DEVICE);
                uap->dmatx.queued = false;
                uap->dmacr &= ~UART011_TXDMAE;
                pl011_write(uap->dmacr, uap, REG_DMACR);
        }
}

static void pl011_dma_rx_callback(void *data);

static int pl011_dma_rx_trigger_dma(struct uart_amba_port *uap)
{
        struct dma_chan *rxchan = uap->dmarx.chan;
        struct pl011_dmarx_data *dmarx = &uap->dmarx;
        struct dma_async_tx_descriptor *desc;
        struct pl011_sgbuf *sgbuf;

        if (!rxchan)
                return -EIO;

        /* Start the RX DMA job */
        sgbuf = uap->dmarx.use_buf_b ?
                &uap->dmarx.sgbuf_b : &uap->dmarx.sgbuf_a;
        desc = dmaengine_prep_slave_sg(rxchan, &sgbuf->sg, 1,
                                        DMA_DEV_TO_MEM,
                                        DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        /*
         * If the DMA engine is busy and cannot prepare a
         * channel, no big deal, the driver will fall back
         * to interrupt mode as a result of this error code.
         */
        if (!desc) {
                uap->dmarx.running = false;
                dmaengine_terminate_all(rxchan);
                return -EBUSY;
        }

        /* Some data to go along to the callback */
        desc->callback = pl011_dma_rx_callback;
        desc->callback_param = uap;
        dmarx->cookie = dmaengine_submit(desc);
        dma_async_issue_pending(rxchan);

        uap->dmacr |= UART011_RXDMAE;
        pl011_write(uap->dmacr, uap, REG_DMACR);
        uap->dmarx.running = true;

        uap->im &= ~UART011_RXIM;
        pl011_write(uap->im, uap, REG_IMSC);

        return 0;
}

/*
 * This is called when either the DMA job is complete, or
 * the FIFO timeout interrupt occurred. This must be called
 * with the port spinlock uap->port.lock held.
 */
static void pl011_dma_rx_chars(struct uart_amba_port *uap,
                               u32 pending, bool use_buf_b,
                               bool readfifo)
{
        struct tty_port *port = &uap->port.state->port;
        struct pl011_sgbuf *sgbuf = use_buf_b ?
                &uap->dmarx.sgbuf_b : &uap->dmarx.sgbuf_a;
        int dma_count = 0;
        u32 fifotaken = 0; /* only used for vdbg() */

        struct pl011_dmarx_data *dmarx = &uap->dmarx;
        int dmataken = 0;

        if (uap->dmarx.poll_rate) {
                /* The data can be taken by polling */
                dmataken = sgbuf->sg.length - dmarx->last_residue;
                /* Recalculate the pending size */
                if (pending >= dmataken)
                        pending -= dmataken;
        }

        /* Pick the remain data from the DMA */
        if (pending) {

                /*
                 * First take all chars in the DMA pipe, then look in the FIFO.
                 * Note that tty_insert_flip_buf() tries to take as many chars
                 * as it can.
                 */
                dma_count = tty_insert_flip_string(port, sgbuf->buf + dmataken,
                                pending);

                uap->port.icount.rx += dma_count;
                if (dma_count < pending)
                        dev_warn(uap->port.dev,
                                 "couldn't insert all characters (TTY is full?)\n");
        }

        /* Reset the last_residue for Rx DMA poll */
        if (uap->dmarx.poll_rate)
                dmarx->last_residue = sgbuf->sg.length;

        /*
         * Only continue with trying to read the FIFO if all DMA chars have
         * been taken first.
         */
        if (dma_count == pending && readfifo) {
                /* Clear any error flags */
                pl011_write(UART011_OEIS | UART011_BEIS | UART011_PEIS |
                            UART011_FEIS, uap, REG_ICR);

                /*
                 * If we read all the DMA'd characters, and we had an
                 * incomplete buffer, that could be due to an rx error, or
                 * maybe we just timed out. Read any pending chars and check
                 * the error status.
                 *
                 * Error conditions will only occur in the FIFO, these will
                 * trigger an immediate interrupt and stop the DMA job, so we
                 * will always find the error in the FIFO, never in the DMA
                 * buffer.
                 */
                fifotaken = pl011_fifo_to_tty(uap);
        }

        spin_unlock(&uap->port.lock);
        dev_vdbg(uap->port.dev,
                 "Took %d chars from DMA buffer and %d chars from the FIFO\n",
                 dma_count, fifotaken);
        tty_flip_buffer_push(port);
        spin_lock(&uap->port.lock);
}

static void pl011_dma_rx_irq(struct uart_amba_port *uap)
{
        struct pl011_dmarx_data *dmarx = &uap->dmarx;
        struct dma_chan *rxchan = dmarx->chan;
        struct pl011_sgbuf *sgbuf = dmarx->use_buf_b ?
                &dmarx->sgbuf_b : &dmarx->sgbuf_a;
        size_t pending;
        struct dma_tx_state state;
        enum dma_status dmastat;

        /*
         * Pause the transfer so we can trust the current counter,
         * do this before we pause the PL011 block, else we may
         * overflow the FIFO.
         */
        if (dmaengine_pause(rxchan))
                dev_err(uap->port.dev, "unable to pause DMA transfer\n");
        dmastat = rxchan->device->device_tx_status(rxchan,
                                                   dmarx->cookie, &state);
        if (dmastat != DMA_PAUSED)
                dev_err(uap->port.dev, "unable to pause DMA transfer\n");

        /* Disable RX DMA - incoming data will wait in the FIFO */
        uap->dmacr &= ~UART011_RXDMAE;
        pl011_write(uap->dmacr, uap, REG_DMACR);
        uap->dmarx.running = false;

        pending = sgbuf->sg.length - state.residue;
        BUG_ON(pending > PL011_DMA_BUFFER_SIZE);
        /* Then we terminate the transfer - we now know our residue */
        dmaengine_terminate_all(rxchan);

        /*
         * This will take the chars we have so far and insert
         * into the framework.
         */
        pl011_dma_rx_chars(uap, pending, dmarx->use_buf_b, true);

        /* Switch buffer & re-trigger DMA job */
        dmarx->use_buf_b = !dmarx->use_buf_b;
        if (pl011_dma_rx_trigger_dma(uap)) {
                dev_dbg(uap->port.dev, "could not retrigger RX DMA job "
                        "fall back to interrupt mode\n");
                uap->im |= UART011_RXIM;
                pl011_write(uap->im, uap, REG_IMSC);
        }
}

static void pl011_dma_rx_callback(void *data)
{
        struct uart_amba_port *uap = data;
        struct pl011_dmarx_data *dmarx = &uap->dmarx;
        struct dma_chan *rxchan = dmarx->chan;
        bool lastbuf = dmarx->use_buf_b;
        struct pl011_sgbuf *sgbuf = dmarx->use_buf_b ?
                &dmarx->sgbuf_b : &dmarx->sgbuf_a;
        size_t pending;
        struct dma_tx_state state;
        int ret;

        /*
         * This completion interrupt occurs typically when the
         * RX buffer is totally stuffed but no timeout has yet
         * occurred. When that happens, we just want the RX
         * routine to flush out the secondary DMA buffer while
         * we immediately trigger the next DMA job.
         */
        spin_lock_irq(&uap->port.lock);
        /*
         * Rx data can be taken by the UART interrupts during
         * the DMA irq handler. So we check the residue here.
         */
        rxchan->device->device_tx_status(rxchan, dmarx->cookie, &state);
        pending = sgbuf->sg.length - state.residue;
        BUG_ON(pending > PL011_DMA_BUFFER_SIZE);
        /* Then we terminate the transfer - we now know our residue */
        dmaengine_terminate_all(rxchan);

        uap->dmarx.running = false;
        dmarx->use_buf_b = !lastbuf;
        ret = pl011_dma_rx_trigger_dma(uap);

        pl011_dma_rx_chars(uap, pending, lastbuf, false);
        spin_unlock_irq(&uap->port.lock);
        /*
         * Do this check after we picked the DMA chars so we don't
         * get some IRQ immediately from RX.
         */
        if (ret) {
                dev_dbg(uap->port.dev, "could not retrigger RX DMA job "
                        "fall back to interrupt mode\n");
                uap->im |= UART011_RXIM;
                pl011_write(uap->im, uap, REG_IMSC);
        }
}

/*
 * Stop accepting received characters, when we're shutting down or
 * suspending this port.
 * Locking: called with port lock held and IRQs disabled.
 */
static inline void pl011_dma_rx_stop(struct uart_amba_port *uap)
{
        /* FIXME.  Just disable the DMA enable */
        uap->dmacr &= ~UART011_RXDMAE;
        pl011_write(uap->dmacr, uap, REG_DMACR);
}

/*
 * Timer handler for Rx DMA polling.
 * Every polling, It checks the residue in the dma buffer and transfer
 * data to the tty. Also, last_residue is updated for the next polling.
 */
static void pl011_dma_rx_poll(struct timer_list *t)
{
        struct uart_amba_port *uap = from_timer(uap, t, dmarx.timer);
        struct tty_port *port = &uap->port.state->port;
        struct pl011_dmarx_data *dmarx = &uap->dmarx;
        struct dma_chan *rxchan = uap->dmarx.chan;
        unsigned long flags = 0;
        unsigned int dmataken = 0;
        unsigned int size = 0;
        struct pl011_sgbuf *sgbuf;
        int dma_count;
        struct dma_tx_state state;

        sgbuf = dmarx->use_buf_b ? &uap->dmarx.sgbuf_b : &uap->dmarx.sgbuf_a;
        rxchan->device->device_tx_status(rxchan, dmarx->cookie, &state);
        if (likely(state.residue < dmarx->last_residue)) {
                dmataken = sgbuf->sg.length - dmarx->last_residue;
                size = dmarx->last_residue - state.residue;
                dma_count = tty_insert_flip_string(port, sgbuf->buf + dmataken,
                                size);
                if (dma_count == size)
                        dmarx->last_residue =  state.residue;
                dmarx->last_jiffies = jiffies;
        }
        tty_flip_buffer_push(port);

        /*
         * If no data is received in poll_timeout, the driver will fall back
         * to interrupt mode. We will retrigger DMA at the first interrupt.
         */
        if (jiffies_to_msecs(jiffies - dmarx->last_jiffies)
                        > uap->dmarx.poll_timeout) {

                spin_lock_irqsave(&uap->port.lock, flags);
                pl011_dma_rx_stop(uap);
                uap->im |= UART011_RXIM;
                pl011_write(uap->im, uap, REG_IMSC);
                spin_unlock_irqrestore(&uap->port.lock, flags);

                uap->dmarx.running = false;
                dmaengine_terminate_all(rxchan);
                del_timer(&uap->dmarx.timer);
        } else {
                mod_timer(&uap->dmarx.timer,
                        jiffies + msecs_to_jiffies(uap->dmarx.poll_rate));
        }
}

static void pl011_dma_startup(struct uart_amba_port *uap)
{
        int ret;

        if (!uap->dma_probed)
                pl011_dma_probe(uap);

        if (!uap->dmatx.chan)
                return;

        uap->dmatx.buf = kmalloc(PL011_DMA_BUFFER_SIZE, GFP_KERNEL | __GFP_DMA);
        if (!uap->dmatx.buf) {
                dev_err(uap->port.dev, "no memory for DMA TX buffer\n");
                uap->port.fifosize = uap->fifosize;
                return;
        }

        sg_init_one(&uap->dmatx.sg, uap->dmatx.buf, PL011_DMA_BUFFER_SIZE);

        /* The DMA buffer is now the FIFO the TTY subsystem can use */
        uap->port.fifosize = PL011_DMA_BUFFER_SIZE;
        uap->using_tx_dma = true;

        if (!uap->dmarx.chan)
                goto skip_rx;

        /* Allocate and map DMA RX buffers */
        ret = pl011_sgbuf_init(uap->dmarx.chan, &uap->dmarx.sgbuf_a,
                               DMA_FROM_DEVICE);
        if (ret) {
                dev_err(uap->port.dev, "failed to init DMA %s: %d\n",
                        "RX buffer A", ret);
                goto skip_rx;
        }

        ret = pl011_sgbuf_init(uap->dmarx.chan, &uap->dmarx.sgbuf_b,
                               DMA_FROM_DEVICE);
        if (ret) {
                dev_err(uap->port.dev, "failed to init DMA %s: %d\n",
                        "RX buffer B", ret);
                pl011_sgbuf_free(uap->dmarx.chan, &uap->dmarx.sgbuf_a,
                                 DMA_FROM_DEVICE);
                goto skip_rx;
        }

        uap->using_rx_dma = true;

skip_rx:
        /* Turn on DMA error (RX/TX will be enabled on demand) */
        uap->dmacr |= UART011_DMAONERR;
        pl011_write(uap->dmacr, uap, REG_DMACR);

        /*
         * ST Micro variants has some specific dma burst threshold
         * compensation. Set this to 16 bytes, so burst will only
         * be issued above/below 16 bytes.
         */
        if (uap->vendor->dma_threshold)
                pl011_write(ST_UART011_DMAWM_RX_16 | ST_UART011_DMAWM_TX_16,
                            uap, REG_ST_DMAWM);

        if (uap->using_rx_dma) {
                if (pl011_dma_rx_trigger_dma(uap))
                        dev_dbg(uap->port.dev, "could not trigger initial "
                                "RX DMA job, fall back to interrupt mode\n");
                if (uap->dmarx.poll_rate) {
                        timer_setup(&uap->dmarx.timer, pl011_dma_rx_poll, 0);
                        mod_timer(&uap->dmarx.timer,
                                jiffies +
                                msecs_to_jiffies(uap->dmarx.poll_rate));
                        uap->dmarx.last_residue = PL011_DMA_BUFFER_SIZE;
                        uap->dmarx.last_jiffies = jiffies;
                }
        }
}

static void pl011_dma_shutdown(struct uart_amba_port *uap)
{
        if (!(uap->using_tx_dma || uap->using_rx_dma))
                return;

        /* Disable RX and TX DMA */
        while (pl011_read(uap, REG_FR) & uap->vendor->fr_busy)
                cpu_relax();

        spin_lock_irq(&uap->port.lock);
        uap->dmacr &= ~(UART011_DMAONERR | UART011_RXDMAE | UART011_TXDMAE);
        pl011_write(uap->dmacr, uap, REG_DMACR);
        spin_unlock_irq(&uap->port.lock);

        if (uap->using_tx_dma) {
                /* In theory, this should already be done by pl011_dma_flush_buffer */
                dmaengine_terminate_all(uap->dmatx.chan);
                if (uap->dmatx.queued) {
                        dma_unmap_sg(uap->dmatx.chan->device->dev, &uap->dmatx.sg, 1,
                                     DMA_TO_DEVICE);
                        uap->dmatx.queued = false;
                }

                kfree(uap->dmatx.buf);
                uap->using_tx_dma = false;
        }

        if (uap->using_rx_dma) {
                dmaengine_terminate_all(uap->dmarx.chan);
                /* Clean up the RX DMA */
                pl011_sgbuf_free(uap->dmarx.chan, &uap->dmarx.sgbuf_a, DMA_FROM_DEVICE);
                pl011_sgbuf_free(uap->dmarx.chan, &uap->dmarx.sgbuf_b, DMA_FROM_DEVICE);
                if (uap->dmarx.poll_rate)
                        del_timer_sync(&uap->dmarx.timer);
                uap->using_rx_dma = false;
        }
}

static inline bool pl011_dma_rx_available(struct uart_amba_port *uap)
{
        return uap->using_rx_dma;
}

static inline bool pl011_dma_rx_running(struct uart_amba_port *uap)
{
        return uap->using_rx_dma && uap->dmarx.running;
}

#else
/* Blank functions if the DMA engine is not available */
static inline void pl011_dma_probe(struct uart_amba_port *uap)
{
}

static inline void pl011_dma_remove(struct uart_amba_port *uap)
{
}

static inline void pl011_dma_startup(struct uart_amba_port *uap)
{
}

static inline void pl011_dma_shutdown(struct uart_amba_port *uap)
{
}

static inline bool pl011_dma_tx_irq(struct uart_amba_port *uap)
{
        return false;
}

static inline void pl011_dma_tx_stop(struct uart_amba_port *uap)
{
}

static inline bool pl011_dma_tx_start(struct uart_amba_port *uap)
{
        return false;
}

static inline void pl011_dma_rx_irq(struct uart_amba_port *uap)
{
}

static inline void pl011_dma_rx_stop(struct uart_amba_port *uap)
{
}

static inline int pl011_dma_rx_trigger_dma(struct uart_amba_port *uap)
{
        return -EIO;
}

static inline bool pl011_dma_rx_available(struct uart_amba_port *uap)
{
        return false;
}

static inline bool pl011_dma_rx_running(struct uart_amba_port *uap)
{
        return false;
}

#define pl011_dma_flush_buffer  NULL
#endif

static void pl011_stop_tx(struct uart_port *port)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);

        uap->im &= ~UART011_TXIM;
        pl011_write(uap->im, uap, REG_IMSC);
        pl011_dma_tx_stop(uap);
}

static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq);

/* Start TX with programmed I/O only (no DMA) */
static void pl011_start_tx_pio(struct uart_amba_port *uap)
{
        if (pl011_tx_chars(uap, false)) {
                uap->im |= UART011_TXIM;
                pl011_write(uap->im, uap, REG_IMSC);
        }
}

static void pl011_start_tx(struct uart_port *port)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);

        if (!pl011_dma_tx_start(uap))
                pl011_start_tx_pio(uap);
}

static void pl011_stop_rx(struct uart_port *port)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);

        uap->im &= ~(UART011_RXIM|UART011_RTIM|UART011_FEIM|
                     UART011_PEIM|UART011_BEIM|UART011_OEIM);
        pl011_write(uap->im, uap, REG_IMSC);

        pl011_dma_rx_stop(uap);
}

static void pl011_enable_ms(struct uart_port *port)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);

        uap->im |= UART011_RIMIM|UART011_CTSMIM|UART011_DCDMIM|UART011_DSRMIM;
        pl011_write(uap->im, uap, REG_IMSC);
}

static void pl011_rx_chars(struct uart_amba_port *uap)
__releases(&uap->port.lock)
__acquires(&uap->port.lock)
{
        pl011_fifo_to_tty(uap);

        spin_unlock(&uap->port.lock);
        tty_flip_buffer_push(&uap->port.state->port);
        /*
         * If we were temporarily out of DMA mode for a while,
         * attempt to switch back to DMA mode again.
         */
        if (pl011_dma_rx_available(uap)) {
                if (pl011_dma_rx_trigger_dma(uap)) {
                        dev_dbg(uap->port.dev, "could not trigger RX DMA job "
                                "fall back to interrupt mode again\n");
                        uap->im |= UART011_RXIM;
                        pl011_write(uap->im, uap, REG_IMSC);
                } else {
#ifdef CONFIG_DMA_ENGINE
                        /* Start Rx DMA poll */
                        if (uap->dmarx.poll_rate) {
                                uap->dmarx.last_jiffies = jiffies;
                                uap->dmarx.last_residue = PL011_DMA_BUFFER_SIZE;
                                mod_timer(&uap->dmarx.timer,
                                        jiffies +
                                        msecs_to_jiffies(uap->dmarx.poll_rate));
                        }
#endif
                }
        }
        spin_lock(&uap->port.lock);
}

static bool pl011_tx_char(struct uart_amba_port *uap, unsigned char c,
                          bool from_irq)
{
        if (unlikely(!from_irq) &&
            pl011_read(uap, REG_FR) & UART01x_FR_TXFF)
                return false; /* unable to transmit character */

        pl011_write(c, uap, REG_DR);
        uap->port.icount.tx++;

        return true;
}

/* Returns true if tx interrupts have to be (kept) enabled  */
static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq)
{
        struct circ_buf *xmit = &uap->port.state->xmit;
        int count = uap->fifosize >> 1;

        if (uap->port.x_char) {
                if (!pl011_tx_char(uap, uap->port.x_char, from_irq))
                        return true;
                uap->port.x_char = 0;
                --count;
        }
        if (uart_circ_empty(xmit) || uart_tx_stopped(&uap->port)) {
                pl011_stop_tx(&uap->port);
                return false;
        }

        /* If we are using DMA mode, try to send some characters. */
        if (pl011_dma_tx_irq(uap))
                return true;

        do {
                if (likely(from_irq) && count-- == 0)
                        break;

                if (!pl011_tx_char(uap, xmit->buf[xmit->tail], from_irq))
                        break;

                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
        } while (!uart_circ_empty(xmit));

        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(&uap->port);

        if (uart_circ_empty(xmit)) {
                pl011_stop_tx(&uap->port);
                return false;
        }
        return true;
}

static void pl011_modem_status(struct uart_amba_port *uap)
{
        unsigned int status, delta;

        status = pl011_read(uap, REG_FR) & UART01x_FR_MODEM_ANY;

        delta = status ^ uap->old_status;
        uap->old_status = status;

        if (!delta)
                return;

        if (delta & UART01x_FR_DCD)
                uart_handle_dcd_change(&uap->port, status & UART01x_FR_DCD);

        if (delta & uap->vendor->fr_dsr)
                uap->port.icount.dsr++;

        if (delta & uap->vendor->fr_cts)
                uart_handle_cts_change(&uap->port,
                                       status & uap->vendor->fr_cts);

        wake_up_interruptible(&uap->port.state->port.delta_msr_wait);
}

static void check_apply_cts_event_workaround(struct uart_amba_port *uap)
{
        unsigned int dummy_read;

        if (!uap->vendor->cts_event_workaround)
                return;

        /* workaround to make sure that all bits are unlocked.. */
        pl011_write(0x00, uap, REG_ICR);

        /*
         * WA: introduce 26ns(1 uart clk) delay before W1C;
         * single apb access will incur 2 pclk(133.12Mhz) delay,
         * so add 2 dummy reads
         */
        dummy_read = pl011_read(uap, REG_ICR);
        dummy_read = pl011_read(uap, REG_ICR);
}

static irqreturn_t pl011_int(int irq, void *dev_id)
{
        struct uart_amba_port *uap = dev_id;
        unsigned long flags;
        unsigned int status, pass_counter = AMBA_ISR_PASS_LIMIT;
        u16 imsc;
        int handled = 0;

        spin_lock_irqsave(&uap->port.lock, flags);
        imsc = pl011_read(uap, REG_IMSC);
        status = pl011_read(uap, REG_RIS) & imsc;
        if (status) {
                do {
                        check_apply_cts_event_workaround(uap);

                        pl011_write(status & ~(UART011_TXIS|UART011_RTIS|
                                               UART011_RXIS),
                                    uap, REG_ICR);

                        if (status & (UART011_RTIS|UART011_RXIS)) {
                                if (pl011_dma_rx_running(uap))
                                        pl011_dma_rx_irq(uap);
                                else
                                        pl011_rx_chars(uap);
                        }
                        if (status & (UART011_DSRMIS|UART011_DCDMIS|
                                      UART011_CTSMIS|UART011_RIMIS))
                                pl011_modem_status(uap);
                        if (status & UART011_TXIS)
                                pl011_tx_chars(uap, true);

                        if (pass_counter-- == 0)
                                break;

                        status = pl011_read(uap, REG_RIS) & imsc;
                } while (status != 0);
                handled = 1;
        }

        spin_unlock_irqrestore(&uap->port.lock, flags);

        return IRQ_RETVAL(handled);
}

static unsigned int pl011_tx_empty(struct uart_port *port)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);

        /* Allow feature register bits to be inverted to work around errata */
        unsigned int status = pl011_read(uap, REG_FR) ^ uap->vendor->inv_fr;

        return status & (uap->vendor->fr_busy | UART01x_FR_TXFF) ?
                                                        0 : TIOCSER_TEMT;
}

static unsigned int pl011_get_mctrl(struct uart_port *port)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);
        unsigned int result = 0;
        unsigned int status = pl011_read(uap, REG_FR);

#define TIOCMBIT(uartbit, tiocmbit)     \
        if (status & uartbit)           \
                result |= tiocmbit

        TIOCMBIT(UART01x_FR_DCD, TIOCM_CAR);
        TIOCMBIT(uap->vendor->fr_dsr, TIOCM_DSR);
        TIOCMBIT(uap->vendor->fr_cts, TIOCM_CTS);
        TIOCMBIT(uap->vendor->fr_ri, TIOCM_RNG);
#undef TIOCMBIT
        return result;
}

static void pl011_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);
        unsigned int cr;

        cr = pl011_read(uap, REG_CR);

#define TIOCMBIT(tiocmbit, uartbit)             \
        if (mctrl & tiocmbit)           \
                cr |= uartbit;          \
        else                            \
                cr &= ~uartbit

        TIOCMBIT(TIOCM_RTS, UART011_CR_RTS);
        TIOCMBIT(TIOCM_DTR, UART011_CR_DTR);
        TIOCMBIT(TIOCM_OUT1, UART011_CR_OUT1);
        TIOCMBIT(TIOCM_OUT2, UART011_CR_OUT2);
        TIOCMBIT(TIOCM_LOOP, UART011_CR_LBE);

        if (port->status & UPSTAT_AUTORTS) {
                /* We need to disable auto-RTS if we want to turn RTS off */
                TIOCMBIT(TIOCM_RTS, UART011_CR_RTSEN);
        }
#undef TIOCMBIT

        pl011_write(cr, uap, REG_CR);
}

static void pl011_break_ctl(struct uart_port *port, int break_state)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);
        unsigned long flags;
        unsigned int lcr_h;

        spin_lock_irqsave(&uap->port.lock, flags);
        lcr_h = pl011_read(uap, REG_LCRH_TX);
        if (break_state == -1)
                lcr_h |= UART01x_LCRH_BRK;
        else
                lcr_h &= ~UART01x_LCRH_BRK;
        pl011_write(lcr_h, uap, REG_LCRH_TX);
        spin_unlock_irqrestore(&uap->port.lock, flags);
}

#ifdef CONFIG_CONSOLE_POLL

static void pl011_quiesce_irqs(struct uart_port *port)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);

        pl011_write(pl011_read(uap, REG_MIS), uap, REG_ICR);
        /*
         * There is no way to clear TXIM as this is "ready to transmit IRQ", so
         * we simply mask it. start_tx() will unmask it.
         *
         * Note we can race with start_tx(), and if the race happens, the
         * polling user might get another interrupt just after we clear it.
         * But it should be OK and can happen even w/o the race, e.g.
         * controller immediately got some new data and raised the IRQ.
         *
         * And whoever uses polling routines assumes that it manages the device
         * (including tx queue), so we're also fine with start_tx()'s caller
         * side.
         */
        pl011_write(pl011_read(uap, REG_IMSC) & ~UART011_TXIM, uap,
                    REG_IMSC);
}

static int pl011_get_poll_char(struct uart_port *port)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);
        unsigned int status;

        /*
         * The caller might need IRQs lowered, e.g. if used with KDB NMI
         * debugger.
         */
        pl011_quiesce_irqs(port);

        status = pl011_read(uap, REG_FR);
        if (status & UART01x_FR_RXFE)
                return NO_POLL_CHAR;

        return pl011_read(uap, REG_DR);
}

static void pl011_put_poll_char(struct uart_port *port,
                         unsigned char ch)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);

        while (pl011_read(uap, REG_FR) & UART01x_FR_TXFF)
                cpu_relax();

        pl011_write(ch, uap, REG_DR);
}

#endif /* CONFIG_CONSOLE_POLL */

static int pl011_hwinit(struct uart_port *port)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);
        int retval;

        /* Optionaly enable pins to be muxed in and configured */
        pinctrl_pm_select_default_state(port->dev);

        /*
         * Try to enable the clock producer.
         */
        retval = clk_prepare_enable(uap->clk);
        if (retval)
                return retval;

        uap->port.uartclk = clk_get_rate(uap->clk);

        /* Clear pending error and receive interrupts */
        pl011_write(UART011_OEIS | UART011_BEIS | UART011_PEIS |
                    UART011_FEIS | UART011_RTIS | UART011_RXIS,
                    uap, REG_ICR);

        /*
         * Save interrupts enable mask, and enable RX interrupts in case if
         * the interrupt is used for NMI entry.
         */
        uap->im = pl011_read(uap, REG_IMSC);
        pl011_write(UART011_RTIM | UART011_RXIM, uap, REG_IMSC);

        if (dev_get_platdata(uap->port.dev)) {
                struct amba_pl011_data *plat;

                plat = dev_get_platdata(uap->port.dev);
                if (plat->init)
                        plat->init();
        }
        return 0;
}

static bool pl011_split_lcrh(const struct uart_amba_port *uap)
{
        return pl011_reg_to_offset(uap, REG_LCRH_RX) !=
               pl011_reg_to_offset(uap, REG_LCRH_TX);
}

static void pl011_write_lcr_h(struct uart_amba_port *uap, unsigned int lcr_h)
{
        pl011_write(lcr_h, uap, REG_LCRH_RX);
        if (pl011_split_lcrh(uap)) {
                int i;
                /*
                 * Wait 10 PCLKs before writing LCRH_TX register,
                 * to get this delay write read only register 10 times
                 */
                for (i = 0; i < 10; ++i)
                        pl011_write(0xff, uap, REG_MIS);
                pl011_write(lcr_h, uap, REG_LCRH_TX);
        }
}

static int pl011_allocate_irq(struct uart_amba_port *uap)
{
        pl011_write(uap->im, uap, REG_IMSC);

        return request_irq(uap->port.irq, pl011_int, 0, "uart-pl011", uap);
}

/*
 * Enable interrupts, only timeouts when using DMA
 * if initial RX DMA job failed, start in interrupt mode
 * as well.
 */
static void pl011_enable_interrupts(struct uart_amba_port *uap)
{
        spin_lock_irq(&uap->port.lock);

        /* Clear out any spuriously appearing RX interrupts */
        pl011_write(UART011_RTIS | UART011_RXIS, uap, REG_ICR);
        uap->im = UART011_RTIM;
        if (!pl011_dma_rx_running(uap))
                uap->im |= UART011_RXIM;
        pl011_write(uap->im, uap, REG_IMSC);
        spin_unlock_irq(&uap->port.lock);
}

static int pl011_startup(struct uart_port *port)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);
        unsigned int cr;
        int retval;

        retval = pl011_hwinit(port);
        if (retval)
                goto clk_dis;

        retval = pl011_allocate_irq(uap);
        if (retval)
                goto clk_dis;

        pl011_write(uap->vendor->ifls, uap, REG_IFLS);

        spin_lock_irq(&uap->port.lock);

        /* restore RTS and DTR */
        cr = uap->old_cr & (UART011_CR_RTS | UART011_CR_DTR);
        cr |= UART01x_CR_UARTEN | UART011_CR_RXE | UART011_CR_TXE;
        pl011_write(cr, uap, REG_CR);

        spin_unlock_irq(&uap->port.lock);

        /*
         * initialise the old status of the modem signals
         */
        uap->old_status = pl011_read(uap, REG_FR) & UART01x_FR_MODEM_ANY;

        /* Startup DMA */
        pl011_dma_startup(uap);

        pl011_enable_interrupts(uap);

        return 0;

 clk_dis:
        clk_disable_unprepare(uap->clk);
        return retval;
}

static int sbsa_uart_startup(struct uart_port *port)
{
        struct uart_amba_port *uap =
                container_of(port, struct uart_amba_port, port);
        int retval;

        retval = pl011_hwinit(port);
        if (retval)
                return retval;

        retval = pl011_allocate_irq(uap);
        if (retval)
                return retval;

        /* The SBSA UART does not support any modem status lines. */
        uap->old_status = 0;

        pl011_enable_interrupts(uap);

        return 0;
}

static void pl011_shutdown_channel(struct uart_amba_port *uap,
                                        unsigned int lcrh)
{
      unsigned long val;

      val = pl011_read(uap, lcrh);
      val &= ~(UART01x_LCRH_BRK | UART01x_LCRH_FEN);
      pl011_write(val, uap, lcrh);
}

/*
 * disable the port. It should not disable RTS and DTR.
 * Also RTS and DTR state should be preserved to restore
 * it during startup().
 */
static void pl011_disable_uart(struct uart_amba_port *uap)
{
        unsigned int cr;

        uap->port.status &= ~(UPSTAT_AUTOCTS | UPSTAT_AUTORTS);
        spin_lock_irq(&uap->port.lock);
        cr = pl011_read(uap, REG_CR);
        uap->old_cr = cr;
        cr &= UART011_CR_RTS | UART011_CR_DTR;
        cr |= UART01x_CR_UARTEN | UART011_CR_TXE;
        pl011_write(cr, uap, REG_CR);
        spin_unlock_irq(&uap->port.lock);

        /*
         * disable break condition and fifos
         */
        pl011_shutdown_channel(uap, REG_LCRH_RX);
        if (pl011_split_lcrh(uap))
                pl011_shutdown_channel(uap, REG_LCRH_TX);
}

static void pl011_disable_interrupts(struct uart_amba_port *uap)
{
        spin_lock_irq(&uap->port.lock);

        /* mask all interrupts and clear all pending ones */
        uap->im = 0;
        pl011_write(uap->im, uap, REG_IMSC);
        pl011_write(0xffff, uap, REG_ICR);

        spin_unlock_irq(&uap->port.lock);
}

static void pl011_shutdown(struct uart_port *port)
{
        struct uart_amba_port *uap =
                container_of(port, struct uart_amba_port, port);

        pl011_disable_interrupts(uap);

        pl011_dma_shutdown(uap);

        free_irq(uap->port.irq, uap);

        pl011_disable_uart(uap);

        /*
         * Shut down the clock producer
         */
        clk_disable_unprepare(uap->clk);
        /* Optionally let pins go into sleep states */
        pinctrl_pm_select_sleep_state(port->dev);

        if (dev_get_platdata(uap->port.dev)) {
                struct amba_pl011_data *plat;

                plat = dev_get_platdata(uap->port.dev);
                if (plat->exit)
                        plat->exit();
        }

        if (uap->port.ops->flush_buffer)
                uap->port.ops->flush_buffer(port);
}

static void sbsa_uart_shutdown(struct uart_port *port)
{
        struct uart_amba_port *uap =
                container_of(port, struct uart_amba_port, port);

        pl011_disable_interrupts(uap);

        free_irq(uap->port.irq, uap);

        if (uap->port.ops->flush_buffer)
                uap->port.ops->flush_buffer(port);
}

static void
pl011_setup_status_masks(struct uart_port *port, struct ktermios *termios)
{
        port->read_status_mask = UART011_DR_OE | 255;
        if (termios->c_iflag & INPCK)
                port->read_status_mask |= UART011_DR_FE | UART011_DR_PE;
        if (termios->c_iflag & (IGNBRK | BRKINT | PARMRK))
                port->read_status_mask |= UART011_DR_BE;

        /*
         * Characters to ignore
         */
        port->ignore_status_mask = 0;
        if (termios->c_iflag & IGNPAR)
                port->ignore_status_mask |= UART011_DR_FE | UART011_DR_PE;
        if (termios->c_iflag & IGNBRK) {
                port->ignore_status_mask |= UART011_DR_BE;
                /*
                 * If we're ignoring parity and break indicators,
                 * ignore overruns too (for real raw support).
                 */
                if (termios->c_iflag & IGNPAR)
                        port->ignore_status_mask |= UART011_DR_OE;
        }

        /*
         * Ignore all characters if CREAD is not set.
         */
        if ((termios->c_cflag & CREAD) == 0)
                port->ignore_status_mask |= UART_DUMMY_DR_RX;
}

static void
pl011_set_termios(struct uart_port *port, struct ktermios *termios,
                     struct ktermios *old)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);
        unsigned int lcr_h, old_cr;
        unsigned long flags;
        unsigned int baud, quot, clkdiv;

        if (uap->vendor->oversampling)
                clkdiv = 8;
        else
                clkdiv = 16;

        /*
         * Ask the core to calculate the divisor for us.
         */
        baud = uart_get_baud_rate(port, termios, old, 0,
                                  port->uartclk / clkdiv);
#ifdef CONFIG_DMA_ENGINE
        /*
         * Adjust RX DMA polling rate with baud rate if not specified.
         */
        if (uap->dmarx.auto_poll_rate)
                uap->dmarx.poll_rate = DIV_ROUND_UP(10000000, baud);
#endif

        if (baud > port->uartclk/16)
                quot = DIV_ROUND_CLOSEST(port->uartclk * 8, baud);
        else
                quot = DIV_ROUND_CLOSEST(port->uartclk * 4, baud);

        switch (termios->c_cflag & CSIZE) {
        case CS5:
                lcr_h = UART01x_LCRH_WLEN_5;
                break;
        case CS6:
                lcr_h = UART01x_LCRH_WLEN_6;
                break;
        case CS7:
                lcr_h = UART01x_LCRH_WLEN_7;
                break;
        default: // CS8
                lcr_h = UART01x_LCRH_WLEN_8;
                break;
        }
        if (termios->c_cflag & CSTOPB)
                lcr_h |= UART01x_LCRH_STP2;
        if (termios->c_cflag & PARENB) {
                lcr_h |= UART01x_LCRH_PEN;
                if (!(termios->c_cflag & PARODD))
                        lcr_h |= UART01x_LCRH_EPS;
                if (termios->c_cflag & CMSPAR)
                        lcr_h |= UART011_LCRH_SPS;
        }
        if (uap->fifosize > 1)
                lcr_h |= UART01x_LCRH_FEN;

        spin_lock_irqsave(&port->lock, flags);

        /*
         * Update the per-port timeout.
         */
        uart_update_timeout(port, termios->c_cflag, baud);

        pl011_setup_status_masks(port, termios);

        if (UART_ENABLE_MS(port, termios->c_cflag))
                pl011_enable_ms(port);

        /* first, disable everything */
        old_cr = pl011_read(uap, REG_CR);
        pl011_write(0, uap, REG_CR);

        if (termios->c_cflag & CRTSCTS) {
                if (old_cr & UART011_CR_RTS)
                        old_cr |= UART011_CR_RTSEN;

                old_cr |= UART011_CR_CTSEN;
                port->status |= UPSTAT_AUTOCTS | UPSTAT_AUTORTS;
        } else {
                old_cr &= ~(UART011_CR_CTSEN | UART011_CR_RTSEN);
                port->status &= ~(UPSTAT_AUTOCTS | UPSTAT_AUTORTS);
        }

        if (uap->vendor->oversampling) {
                if (baud > port->uartclk / 16)
                        old_cr |= ST_UART011_CR_OVSFACT;
                else
                        old_cr &= ~ST_UART011_CR_OVSFACT;
        }

        /*
         * Workaround for the ST Micro oversampling variants to
         * increase the bitrate slightly, by lowering the divisor,
         * to avoid delayed sampling of start bit at high speeds,
         * else we see data corruption.
         */
        if (uap->vendor->oversampling) {
                if ((baud >= 3000000) && (baud < 3250000) && (quot > 1))
                        quot -= 1;
                else if ((baud > 3250000) && (quot > 2))
                        quot -= 2;
        }
        /* Set baud rate */
        pl011_write(quot & 0x3f, uap, REG_FBRD);
        pl011_write(quot >> 6, uap, REG_IBRD);

        /*
         * ----------v----------v----------v----------v-----
         * NOTE: REG_LCRH_TX and REG_LCRH_RX MUST BE WRITTEN AFTER
         * REG_FBRD & REG_IBRD.
         * ----------^----------^----------^----------^-----
         */
        pl011_write_lcr_h(uap, lcr_h);
        pl011_write(old_cr, uap, REG_CR);

        spin_unlock_irqrestore(&port->lock, flags);
}

static void
sbsa_uart_set_termios(struct uart_port *port, struct ktermios *termios,
                      struct ktermios *old)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);
        unsigned long flags;

        tty_termios_encode_baud_rate(termios, uap->fixed_baud, uap->fixed_baud);

        /* The SBSA UART only supports 8n1 without hardware flow control. */
        termios->c_cflag &= ~(CSIZE | CSTOPB | PARENB | PARODD);
        termios->c_cflag &= ~(CMSPAR | CRTSCTS);
        termios->c_cflag |= CS8 | CLOCAL;

        spin_lock_irqsave(&port->lock, flags);
        uart_update_timeout(port, CS8, uap->fixed_baud);
        pl011_setup_status_masks(port, termios);
        spin_unlock_irqrestore(&port->lock, flags);
}

static const char *pl011_type(struct uart_port *port)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);
        return uap->port.type == PORT_AMBA ? uap->type : NULL;
}

/*
 * Release the memory region(s) being used by 'port'
 */
static void pl011_release_port(struct uart_port *port)
{
        release_mem_region(port->mapbase, SZ_4K);
}

/*
 * Request the memory region(s) being used by 'port'
 */
static int pl011_request_port(struct uart_port *port)
{
        return request_mem_region(port->mapbase, SZ_4K, "uart-pl011")
                        != NULL ? 0 : -EBUSY;
}

/*
 * Configure/autoconfigure the port.
 */
static void pl011_config_port(struct uart_port *port, int flags)
{
        if (flags & UART_CONFIG_TYPE) {
                port->type = PORT_AMBA;
                pl011_request_port(port);
        }
}

/*
 * verify the new serial_struct (for TIOCSSERIAL).
 */
static int pl011_verify_port(struct uart_port *port, struct serial_struct *ser)
{
        int ret = 0;
        if (ser->type != PORT_UNKNOWN && ser->type != PORT_AMBA)
                ret = -EINVAL;
        if (ser->irq < 0 || ser->irq >= nr_irqs)
                ret = -EINVAL;
        if (ser->baud_base < 9600)
                ret = -EINVAL;
        return ret;
}

static const struct uart_ops amba_pl011_pops = {
        .tx_empty       = pl011_tx_empty,
        .set_mctrl      = pl011_set_mctrl,
        .get_mctrl      = pl011_get_mctrl,
        .stop_tx        = pl011_stop_tx,
        .start_tx       = pl011_start_tx,
        .stop_rx        = pl011_stop_rx,
        .enable_ms      = pl011_enable_ms,
        .break_ctl      = pl011_break_ctl,
        .startup        = pl011_startup,
        .shutdown       = pl011_shutdown,
        .flush_buffer   = pl011_dma_flush_buffer,
        .set_termios    = pl011_set_termios,
        .type           = pl011_type,
        .release_port   = pl011_release_port,
        .request_port   = pl011_request_port,
        .config_port    = pl011_config_port,
        .verify_port    = pl011_verify_port,
#ifdef CONFIG_CONSOLE_POLL
        .poll_init     = pl011_hwinit,
        .poll_get_char = pl011_get_poll_char,
        .poll_put_char = pl011_put_poll_char,
#endif
};

static void sbsa_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
}

static unsigned int sbsa_uart_get_mctrl(struct uart_port *port)
{
        return 0;
}

static const struct uart_ops sbsa_uart_pops = {
        .tx_empty       = pl011_tx_empty,
        .set_mctrl      = sbsa_uart_set_mctrl,
        .get_mctrl      = sbsa_uart_get_mctrl,
        .stop_tx        = pl011_stop_tx,
        .start_tx       = pl011_start_tx,
        .stop_rx        = pl011_stop_rx,
        .startup        = sbsa_uart_startup,
        .shutdown       = sbsa_uart_shutdown,
        .set_termios    = sbsa_uart_set_termios,
        .type           = pl011_type,
        .release_port   = pl011_release_port,
        .request_port   = pl011_request_port,
        .config_port    = pl011_config_port,
        .verify_port    = pl011_verify_port,
#ifdef CONFIG_CONSOLE_POLL
        .poll_init     = pl011_hwinit,
        .poll_get_char = pl011_get_poll_char,
        .poll_put_char = pl011_put_poll_char,
#endif
};

static struct uart_amba_port *amba_ports[UART_NR];

#ifdef CONFIG_SERIAL_AMBA_PL011_CONSOLE

static void pl011_console_putchar(struct uart_port *port, int ch)
{
        struct uart_amba_port *uap =
            container_of(port, struct uart_amba_port, port);

        while (pl011_read(uap, REG_FR) & UART01x_FR_TXFF)
                cpu_relax();
        pl011_write(ch, uap, REG_DR);
}

static void
pl011_console_write(struct console *co, const char *s, unsigned int count)
{
        struct uart_amba_port *uap = amba_ports[co->index];
        unsigned int old_cr = 0, new_cr;
        unsigned long flags;
        int locked = 1;

        clk_enable(uap->clk);

        local_irq_save(flags);
        if (uap->port.sysrq)
                locked = 0;
        else if (oops_in_progress)
                locked = spin_trylock(&uap->port.lock);
        else
                spin_lock(&uap->port.lock);

        /*
         *      First save the CR then disable the interrupts
         */
        if (!uap->vendor->always_enabled) {
                old_cr = pl011_read(uap, REG_CR);
                new_cr = old_cr & ~UART011_CR_CTSEN;
                new_cr |= UART01x_CR_UARTEN | UART011_CR_TXE;
                pl011_write(new_cr, uap, REG_CR);
        }

        uart_console_write(&uap->port, s, count, pl011_console_putchar);

        /*
         *      Finally, wait for transmitter to become empty and restore the
         *      TCR. Allow feature register bits to be inverted to work around
         *      errata.
         */
        while ((pl011_read(uap, REG_FR) ^ uap->vendor->inv_fr)
                                                & uap->vendor->fr_busy)
                cpu_relax();
        if (!uap->vendor->always_enabled)
                pl011_write(old_cr, uap, REG_CR);

        if (locked)
                spin_unlock(&uap->port.lock);
        local_irq_restore(flags);

        clk_disable(uap->clk);
}

static void __init
pl011_console_get_options(struct uart_amba_port *uap, int *baud,
                             int *parity, int *bits)
{
        if (pl011_read(uap, REG_CR) & UART01x_CR_UARTEN) {
                unsigned int lcr_h, ibrd, fbrd;

                lcr_h = pl011_read(uap, REG_LCRH_TX);

                *parity = 'n';
                if (lcr_h & UART01x_LCRH_PEN) {
                        if (lcr_h & UART01x_LCRH_EPS)
                                *parity = 'e';
                        else
                                *parity = 'o';
                }

                if ((lcr_h & 0x60) == UART01x_LCRH_WLEN_7)
                        *bits = 7;
                else
                        *bits = 8;

                ibrd = pl011_read(uap, REG_IBRD);
                fbrd = pl011_read(uap, REG_FBRD);

                *baud = uap->port.uartclk * 4 / (64 * ibrd + fbrd);

                if (uap->vendor->oversampling) {
                        if (pl011_read(uap, REG_CR)
                                  & ST_UART011_CR_OVSFACT)
                                *baud *= 2;
                }
        }
}

static int __init pl011_console_setup(struct console *co, char *options)
{
        struct uart_amba_port *uap;
        int baud = 38400;
        int bits = 8;
        int parity = 'n';
        int flow = 'n';
        int ret;

        /*
         * Check whether an invalid uart number has been specified, and
         * if so, search for the first available port that does have
         * console support.
         */
        if (co->index >= UART_NR)
                co->index = 0;
        uap = amba_ports[co->index];
        if (!uap)
                return -ENODEV;

        /* Allow pins to be muxed in and configured */
        pinctrl_pm_select_default_state(uap->port.dev);

        ret = clk_prepare(uap->clk);
        if (ret)
                return ret;

        if (dev_get_platdata(uap->port.dev)) {
                struct amba_pl011_data *plat;

                plat = dev_get_platdata(uap->port.dev);
                if (plat->init)
                        plat->init();
        }

        uap->port.uartclk = clk_get_rate(uap->clk);

        if (uap->vendor->fixed_options) {
                baud = uap->fixed_baud;
        } else {
                if (options)
                        uart_parse_options(options,
                                           &baud, &parity, &bits, &flow);
                else
                        pl011_console_get_options(uap, &baud, &parity, &bits);
        }

        return uart_set_options(&uap->port, co, baud, parity, bits, flow);
}

/**
 *      pl011_console_match - non-standard console matching
 *      @co:      registering console
 *      @name:    name from console command line
 *      @idx:     index from console command line
 *      @options: ptr to option string from console command line
 *
 *      Only attempts to match console command lines of the form:
 *          console=pl011,mmio|mmio32,<addr>[,<options>]
 *          console=pl011,0x<addr>[,<options>]
 *      This form is used to register an initial earlycon boot console and
 *      replace it with the amba_console at pl011 driver init.
 *
 *      Performs console setup for a match (as required by interface)
 *      If no <options> are specified, then assume the h/w is already setup.
 *
 *      Returns 0 if console matches; otherwise non-zero to use default matching
 */
static int __init pl011_console_match(struct console *co, char *name, int idx,
                                      char *options)
{
        unsigned char iotype;
        resource_size_t addr;
        int i;

        /*
         * Systems affected by the Qualcomm Technologies QDF2400 E44 erratum
         * have a distinct console name, so make sure we check for that.
         * The actual implementation of the erratum occurs in the probe
         * function.
         */
        if ((strcmp(name, "qdf2400_e44") != 0) && (strcmp(name, "pl011") != 0))
                return -ENODEV;

        if (uart_parse_earlycon(options, &iotype, &addr, &options))
                return -ENODEV;

        if (iotype != UPIO_MEM && iotype != UPIO_MEM32)
                return -ENODEV;

        /* try to match the port specified on the command line */
        for (i = 0; i < ARRAY_SIZE(amba_ports); i++) {
                struct uart_port *port;

                if (!amba_ports[i])
                        continue;

                port = &amba_ports[i]->port;

                if (port->mapbase != addr)
                        continue;

                co->index = i;
                port->cons = co;
                return pl011_console_setup(co, options);
        }

        return -ENODEV;
}

static struct uart_driver amba_reg;
static struct console amba_console = {
        .name           = "ttyAMA",
        .write          = pl011_console_write,
        .device         = uart_console_device,
        .setup          = pl011_console_setup,
        .match          = pl011_console_match,
        .flags          = CON_PRINTBUFFER | CON_ANYTIME,
        .index          = -1,
        .data           = &amba_reg,
};

#define AMBA_CONSOLE    (&amba_console)

static void qdf2400_e44_putc(struct uart_port *port, int c)
{
        while (readl(port->membase + UART01x_FR) & UART01x_FR_TXFF)
                cpu_relax();
        writel(c, port->membase + UART01x_DR);
        while (!(readl(port->membase + UART01x_FR) & UART011_FR_TXFE))
                cpu_relax();
}

static void qdf2400_e44_early_write(struct console *con, const char *s, unsigned n)
{
        struct earlycon_device *dev = con->data;

        uart_console_write(&dev->port, s, n, qdf2400_e44_putc);
}

static void pl011_putc(struct uart_port *port, int c)
{
        while (readl(port->membase + UART01x_FR) & UART01x_FR_TXFF)
                cpu_relax();
        if (port->iotype == UPIO_MEM32)
                writel(c, port->membase + UART01x_DR);
        else
                writeb(c, port->membase + UART01x_DR);
        while (readl(port->membase + UART01x_FR) & UART01x_FR_BUSY)
                cpu_relax();
}

static void pl011_early_write(struct console *con, const char *s, unsigned n)
{
        struct earlycon_device *dev = con->data;

        uart_console_write(&dev->port, s, n, pl011_putc);
}

/*
 * On non-ACPI systems, earlycon is enabled by specifying
 * "earlycon=pl011,<address>" on the kernel command line.
 *
 * On ACPI ARM64 systems, an "early" console is enabled via the SPCR table,
 * by specifying only "earlycon" on the command line.  Because it requires
 * SPCR, the console starts after ACPI is parsed, which is later than a
 * traditional early console.
 *
 * To get the traditional early console that starts before ACPI is parsed,
 * specify the full "earlycon=pl011,<address>" option.
 */
static int __init pl011_early_console_setup(struct earlycon_device *device,
                                            const char *opt)
{
        if (!device->port.membase)
                return -ENODEV;

        device->con->write = pl011_early_write;

        return 0;
}
OF_EARLYCON_DECLARE(pl011, "arm,pl011", pl011_early_console_setup);
OF_EARLYCON_DECLARE(pl011, "arm,sbsa-uart", pl011_early_console_setup);

/*
 * On Qualcomm Datacenter Technologies QDF2400 SOCs affected by
 * Erratum 44, traditional earlycon can be enabled by specifying
 * "earlycon=qdf2400_e44,<address>".  Any options are ignored.
 *
 * Alternatively, you can just specify "earlycon", and the early console
 * will be enabled with the information from the SPCR table.  In this
 * case, the SPCR code will detect the need for the E44 work-around,
 * and set the console name to "qdf2400_e44".
 */
static int __init
qdf2400_e44_early_console_setup(struct earlycon_device *device,
                                const char *opt)
{
        if (!device->port.membase)
                return -ENODEV;

        device->con->write = qdf2400_e44_early_write;
        return 0;
}
EARLYCON_DECLARE(qdf2400_e44, qdf2400_e44_early_console_setup);

#else
#define AMBA_CONSOLE    NULL
#endif

static struct uart_driver amba_reg = {
        .owner                  = THIS_MODULE,
        .driver_name            = "ttyAMA",
        .dev_name               = "ttyAMA",
        .major                  = SERIAL_AMBA_MAJOR,
        .minor                  = SERIAL_AMBA_MINOR,
        .nr                     = UART_NR,
        .cons                   = AMBA_CONSOLE,
};

static int pl011_probe_dt_alias(int index, struct device *dev)
{
        struct device_node *np;
        static bool seen_dev_with_alias = false;
        static bool seen_dev_without_alias = false;
        int ret = index;

        if (!IS_ENABLED(CONFIG_OF))
                return ret;

        np = dev->of_node;
        if (!np)
                return ret;

        ret = of_alias_get_id(np, "serial");
        if (ret < 0) {
                seen_dev_without_alias = true;
                ret = index;
        } else {
                seen_dev_with_alias = true;
                if (ret >= ARRAY_SIZE(amba_ports) || amba_ports[ret] != NULL) {
                        dev_warn(dev, "requested serial port %d  not available.\n", ret);
                        ret = index;
                }
        }

        if (seen_dev_with_alias && seen_dev_without_alias)
                dev_warn(dev, "aliased and non-aliased serial devices found in device tree. Serial port enumeration may be unpredictable.\n");

        return ret;
}

/* unregisters the driver also if no more ports are left */
static void pl011_unregister_port(struct uart_amba_port *uap)
{
        int i;
        bool busy = false;

        for (i = 0; i < ARRAY_SIZE(amba_ports); i++) {
                if (amba_ports[i] == uap)
                        amba_ports[i] = NULL;
                else if (amba_ports[i])
                        busy = true;
        }
        pl011_dma_remove(uap);
        if (!busy)
                uart_unregister_driver(&amba_reg);
}

static int pl011_find_free_port(void)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(amba_ports); i++)
                if (amba_ports[i] == NULL)
                        return i;

        return -EBUSY;
}

static int pl011_setup_port(struct device *dev, struct uart_amba_port *uap,
                            struct resource *mmiobase, int index)
{
        void __iomem *base;

        base = devm_ioremap_resource(dev, mmiobase);
        if (IS_ERR(base))
                return PTR_ERR(base);

        index = pl011_probe_dt_alias(index, dev);

        uap->old_cr = 0;
        uap->port.dev = dev;
        uap->port.mapbase = mmiobase->start;
        uap->port.membase = base;
        uap->port.fifosize = uap->fifosize;
        uap->port.flags = UPF_BOOT_AUTOCONF;
        uap->port.line = index;

        amba_ports[index] = uap;

        return 0;
}

static int pl011_register_port(struct uart_amba_port *uap)
{
        int ret;

        /* Ensure interrupts from this UART are masked and cleared */
        pl011_write(0, uap, REG_IMSC);
        pl011_write(0xffff, uap, REG_ICR);

        if (!amba_reg.state) {
                ret = uart_register_driver(&amba_reg);
                if (ret < 0) {
                        dev_err(uap->port.dev,
                                "Failed to register AMBA-PL011 driver\n");
                        return ret;
                }
        }

        ret = uart_add_one_port(&amba_reg, &uap->port);
        if (ret)
                pl011_unregister_port(uap);

        return ret;
}

static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
{
        struct uart_amba_port *uap;
        struct vendor_data *vendor = id->data;
        int portnr, ret;

        portnr = pl011_find_free_port();
        if (portnr < 0)
                return portnr;

        uap = devm_kzalloc(&dev->dev, sizeof(struct uart_amba_port),
                           GFP_KERNEL);
        if (!uap)
                return -ENOMEM;

        uap->clk = devm_clk_get(&dev->dev, NULL);
        if (IS_ERR(uap->clk))
                return PTR_ERR(uap->clk);

        uap->reg_offset = vendor->reg_offset;
        uap->vendor = vendor;
        uap->fifosize = vendor->get_fifosize(dev);
        uap->port.iotype = vendor->access_32b ? UPIO_MEM32 : UPIO_MEM;
        uap->port.irq = dev->irq[0];
        uap->port.ops = &amba_pl011_pops;

        snprintf(uap->type, sizeof(uap->type), "PL011 rev%u", amba_rev(dev));

        ret = pl011_setup_port(&dev->dev, uap, &dev->res, portnr);
        if (ret)
                return ret;

        amba_set_drvdata(dev, uap);

        return pl011_register_port(uap);
}

static int pl011_remove(struct amba_device *dev)
{
        struct uart_amba_port *uap = amba_get_drvdata(dev);

        uart_remove_one_port(&amba_reg, &uap->port);
        pl011_unregister_port(uap);
        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int pl011_suspend(struct device *dev)
{
        struct uart_amba_port *uap = dev_get_drvdata(dev);

        if (!uap)
                return -EINVAL;

        return uart_suspend_port(&amba_reg, &uap->port);
}

static int pl011_resume(struct device *dev)
{
        struct uart_amba_port *uap = dev_get_drvdata(dev);

        if (!uap)
                return -EINVAL;

        return uart_resume_port(&amba_reg, &uap->port);
}
#endif

static SIMPLE_DEV_PM_OPS(pl011_dev_pm_ops, pl011_suspend, pl011_resume);

static int sbsa_uart_probe(struct platform_device *pdev)
{
        struct uart_amba_port *uap;
        struct resource *r;
        int portnr, ret;
        int baudrate;

        /*
         * Check the mandatory baud rate parameter in the DT node early
         * so that we can easily exit with the error.
         */
        if (pdev->dev.of_node) {
                struct device_node *np = pdev->dev.of_node;

                ret = of_property_read_u32(np, "current-speed", &baudrate);
                if (ret)
                        return ret;
        } else {
                baudrate = 115200;
        }

        portnr = pl011_find_free_port();
        if (portnr < 0)
                return portnr;

        uap = devm_kzalloc(&pdev->dev, sizeof(struct uart_amba_port),
                           GFP_KERNEL);
        if (!uap)
                return -ENOMEM;

        ret = platform_get_irq(pdev, 0);
        if (ret < 0) {
                if (ret != -EPROBE_DEFER)
                        dev_err(&pdev->dev, "cannot obtain irq\n");
                return ret;
        }
        uap->port.irq   = ret;

#ifdef CONFIG_ACPI_SPCR_TABLE
        if (qdf2400_e44_present) {
                dev_info(&pdev->dev, "working around QDF2400 SoC erratum 44\n");
                uap->vendor = &vendor_qdt_qdf2400_e44;
        } else
#endif
                uap->vendor = &vendor_sbsa;

        uap->reg_offset = uap->vendor->reg_offset;
        uap->fifosize   = 32;
        uap->port.iotype = uap->vendor->access_32b ? UPIO_MEM32 : UPIO_MEM;
        uap->port.ops   = &sbsa_uart_pops;
        uap->fixed_baud = baudrate;

        snprintf(uap->type, sizeof(uap->type), "SBSA");

        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);

        ret = pl011_setup_port(&pdev->dev, uap, r, portnr);
        if (ret)
                return ret;

        platform_set_drvdata(pdev, uap);

        return pl011_register_port(uap);
}

static int sbsa_uart_remove(struct platform_device *pdev)
{
        struct uart_amba_port *uap = platform_get_drvdata(pdev);

        uart_remove_one_port(&amba_reg, &uap->port);
        pl011_unregister_port(uap);
        return 0;
}

static const struct of_device_id sbsa_uart_of_match[] = {
        { .compatible = "arm,sbsa-uart", },
        {},
};
MODULE_DEVICE_TABLE(of, sbsa_uart_of_match);

static const struct acpi_device_id sbsa_uart_acpi_match[] = {
        { "ARMH0011", 0 },
        {},
};
MODULE_DEVICE_TABLE(acpi, sbsa_uart_acpi_match);

static struct platform_driver arm_sbsa_uart_platform_driver = {
        .probe          = sbsa_uart_probe,
        .remove         = sbsa_uart_remove,
        .driver = {
                .name   = "sbsa-uart",
                .of_match_table = of_match_ptr(sbsa_uart_of_match),
                .acpi_match_table = ACPI_PTR(sbsa_uart_acpi_match),
        },
};

static const struct amba_id pl011_ids[] = {
        {
                .id     = 0x00041011,
                .mask   = 0x000fffff,
                .data   = &vendor_arm,
        },
        {
                .id     = 0x00380802,
                .mask   = 0x00ffffff,
                .data   = &vendor_st,
        },
        {
                .id     = AMBA_LINUX_ID(0x00, 0x1, 0xffe),
                .mask   = 0x00ffffff,
                .data   = &vendor_zte,
        },
        { 0, 0 },
};

MODULE_DEVICE_TABLE(amba, pl011_ids);

static struct amba_driver pl011_driver = {
        .drv = {
                .name   = "uart-pl011",
                .pm     = &pl011_dev_pm_ops,
        },
        .id_table       = pl011_ids,
        .probe          = pl011_probe,
        .remove         = pl011_remove,
};

static int __init pl011_init(void)
{
        printk(KERN_INFO "Serial: AMBA PL011 UART driver\n");

        if (platform_driver_register(&arm_sbsa_uart_platform_driver))
                pr_warn("could not register SBSA UART platform driver\n");
        return amba_driver_register(&pl011_driver);
}

static void __exit pl011_exit(void)
{
        platform_driver_unregister(&arm_sbsa_uart_platform_driver);
        amba_driver_unregister(&pl011_driver);
}

/*
 * While this can be a module, if builtin it's most likely the console
 * So let's leave module_exit but move module_init to an earlier place
 */
arch_initcall(pl011_init);
module_exit(pl011_exit);

MODULE_AUTHOR("ARM Ltd/Deep Blue Solutions Ltd");
MODULE_DESCRIPTION("ARM AMBA serial port driver");
MODULE_LICENSE("GPL");