Merge tag 'drm-misc-fixes-2018-02-21' of git://anongit.freedesktop.org/drm/drm-misc...

[mirror_ubuntu-hirsute-kernel.git] / drivers / spi / spi-armada-3700.c

/*
 * Marvell Armada-3700 SPI controller driver
 *
 * Copyright (C) 2016 Marvell Ltd.
 *
 * Author: Wilson Ding <dingwei@marvell.com>
 * Author: Romain Perier <romain.perier@free-electrons.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/of_device.h>
#include <linux/pinctrl/consumer.h>
#include <linux/spi/spi.h>

#define DRIVER_NAME                     "armada_3700_spi"

#define A3700_SPI_MAX_SPEED_HZ          100000000
#define A3700_SPI_MAX_PRESCALE          30
#define A3700_SPI_TIMEOUT               10

/* SPI Register Offest */
#define A3700_SPI_IF_CTRL_REG           0x00
#define A3700_SPI_IF_CFG_REG            0x04
#define A3700_SPI_DATA_OUT_REG          0x08
#define A3700_SPI_DATA_IN_REG           0x0C
#define A3700_SPI_IF_INST_REG           0x10
#define A3700_SPI_IF_ADDR_REG           0x14
#define A3700_SPI_IF_RMODE_REG          0x18
#define A3700_SPI_IF_HDR_CNT_REG        0x1C
#define A3700_SPI_IF_DIN_CNT_REG        0x20
#define A3700_SPI_IF_TIME_REG           0x24
#define A3700_SPI_INT_STAT_REG          0x28
#define A3700_SPI_INT_MASK_REG          0x2C

/* A3700_SPI_IF_CTRL_REG */
#define A3700_SPI_EN                    BIT(16)
#define A3700_SPI_ADDR_NOT_CONFIG       BIT(12)
#define A3700_SPI_WFIFO_OVERFLOW        BIT(11)
#define A3700_SPI_WFIFO_UNDERFLOW       BIT(10)
#define A3700_SPI_RFIFO_OVERFLOW        BIT(9)
#define A3700_SPI_RFIFO_UNDERFLOW       BIT(8)
#define A3700_SPI_WFIFO_FULL            BIT(7)
#define A3700_SPI_WFIFO_EMPTY           BIT(6)
#define A3700_SPI_RFIFO_FULL            BIT(5)
#define A3700_SPI_RFIFO_EMPTY           BIT(4)
#define A3700_SPI_WFIFO_RDY             BIT(3)
#define A3700_SPI_RFIFO_RDY             BIT(2)
#define A3700_SPI_XFER_RDY              BIT(1)
#define A3700_SPI_XFER_DONE             BIT(0)

/* A3700_SPI_IF_CFG_REG */
#define A3700_SPI_WFIFO_THRS            BIT(28)
#define A3700_SPI_RFIFO_THRS            BIT(24)
#define A3700_SPI_AUTO_CS               BIT(20)
#define A3700_SPI_DMA_RD_EN             BIT(18)
#define A3700_SPI_FIFO_MODE             BIT(17)
#define A3700_SPI_SRST                  BIT(16)
#define A3700_SPI_XFER_START            BIT(15)
#define A3700_SPI_XFER_STOP             BIT(14)
#define A3700_SPI_INST_PIN              BIT(13)
#define A3700_SPI_ADDR_PIN              BIT(12)
#define A3700_SPI_DATA_PIN1             BIT(11)
#define A3700_SPI_DATA_PIN0             BIT(10)
#define A3700_SPI_FIFO_FLUSH            BIT(9)
#define A3700_SPI_RW_EN                 BIT(8)
#define A3700_SPI_CLK_POL               BIT(7)
#define A3700_SPI_CLK_PHA               BIT(6)
#define A3700_SPI_BYTE_LEN              BIT(5)
#define A3700_SPI_CLK_PRESCALE          BIT(0)
#define A3700_SPI_CLK_PRESCALE_MASK     (0x1f)
#define A3700_SPI_CLK_EVEN_OFFS         (0x10)

#define A3700_SPI_WFIFO_THRS_BIT        28
#define A3700_SPI_RFIFO_THRS_BIT        24
#define A3700_SPI_FIFO_THRS_MASK        0x7

#define A3700_SPI_DATA_PIN_MASK         0x3

/* A3700_SPI_IF_HDR_CNT_REG */
#define A3700_SPI_DUMMY_CNT_BIT         12
#define A3700_SPI_DUMMY_CNT_MASK        0x7
#define A3700_SPI_RMODE_CNT_BIT         8
#define A3700_SPI_RMODE_CNT_MASK        0x3
#define A3700_SPI_ADDR_CNT_BIT          4
#define A3700_SPI_ADDR_CNT_MASK         0x7
#define A3700_SPI_INSTR_CNT_BIT         0
#define A3700_SPI_INSTR_CNT_MASK        0x3

/* A3700_SPI_IF_TIME_REG */
#define A3700_SPI_CLK_CAPT_EDGE         BIT(7)

struct a3700_spi {
        struct spi_master *master;
        void __iomem *base;
        struct clk *clk;
        unsigned int irq;
        unsigned int flags;
        bool xmit_data;
        const u8 *tx_buf;
        u8 *rx_buf;
        size_t buf_len;
        u8 byte_len;
        u32 wait_mask;
        struct completion done;
};

static u32 spireg_read(struct a3700_spi *a3700_spi, u32 offset)
{
        return readl(a3700_spi->base + offset);
}

static void spireg_write(struct a3700_spi *a3700_spi, u32 offset, u32 data)
{
        writel(data, a3700_spi->base + offset);
}

static void a3700_spi_auto_cs_unset(struct a3700_spi *a3700_spi)
{
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        val &= ~A3700_SPI_AUTO_CS;
        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);
}

static void a3700_spi_activate_cs(struct a3700_spi *a3700_spi, unsigned int cs)
{
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CTRL_REG);
        val |= (A3700_SPI_EN << cs);
        spireg_write(a3700_spi, A3700_SPI_IF_CTRL_REG, val);
}

static void a3700_spi_deactivate_cs(struct a3700_spi *a3700_spi,
                                    unsigned int cs)
{
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CTRL_REG);
        val &= ~(A3700_SPI_EN << cs);
        spireg_write(a3700_spi, A3700_SPI_IF_CTRL_REG, val);
}

static int a3700_spi_pin_mode_set(struct a3700_spi *a3700_spi,
                                  unsigned int pin_mode, bool receiving)
{
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        val &= ~(A3700_SPI_INST_PIN | A3700_SPI_ADDR_PIN);
        val &= ~(A3700_SPI_DATA_PIN0 | A3700_SPI_DATA_PIN1);

        switch (pin_mode) {
        case SPI_NBITS_SINGLE:
                break;
        case SPI_NBITS_DUAL:
                val |= A3700_SPI_DATA_PIN0;
                break;
        case SPI_NBITS_QUAD:
                val |= A3700_SPI_DATA_PIN1;
                /* RX during address reception uses 4-pin */
                if (receiving)
                        val |= A3700_SPI_ADDR_PIN;
                break;
        default:
                dev_err(&a3700_spi->master->dev, "wrong pin mode %u", pin_mode);
                return -EINVAL;
        }

        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);

        return 0;
}

static void a3700_spi_fifo_mode_set(struct a3700_spi *a3700_spi, bool enable)
{
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        if (enable)
                val |= A3700_SPI_FIFO_MODE;
        else
                val &= ~A3700_SPI_FIFO_MODE;
        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);
}

static void a3700_spi_mode_set(struct a3700_spi *a3700_spi,
                               unsigned int mode_bits)
{
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);

        if (mode_bits & SPI_CPOL)
                val |= A3700_SPI_CLK_POL;
        else
                val &= ~A3700_SPI_CLK_POL;

        if (mode_bits & SPI_CPHA)
                val |= A3700_SPI_CLK_PHA;
        else
                val &= ~A3700_SPI_CLK_PHA;

        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);
}

static void a3700_spi_clock_set(struct a3700_spi *a3700_spi,
                                unsigned int speed_hz)
{
        u32 val;
        u32 prescale;

        prescale = DIV_ROUND_UP(clk_get_rate(a3700_spi->clk), speed_hz);

        /* For prescaler values over 15, we can only set it by steps of 2.
         * Starting from A3700_SPI_CLK_EVEN_OFFS, we set values from 0 up to
         * 30. We only use this range from 16 to 30.
         */
        if (prescale > 15)
                prescale = A3700_SPI_CLK_EVEN_OFFS + DIV_ROUND_UP(prescale, 2);

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        val = val & ~A3700_SPI_CLK_PRESCALE_MASK;

        val = val | (prescale & A3700_SPI_CLK_PRESCALE_MASK);
        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);

        if (prescale <= 2) {
                val = spireg_read(a3700_spi, A3700_SPI_IF_TIME_REG);
                val |= A3700_SPI_CLK_CAPT_EDGE;
                spireg_write(a3700_spi, A3700_SPI_IF_TIME_REG, val);
        }
}

static void a3700_spi_bytelen_set(struct a3700_spi *a3700_spi, unsigned int len)
{
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        if (len == 4)
                val |= A3700_SPI_BYTE_LEN;
        else
                val &= ~A3700_SPI_BYTE_LEN;
        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);

        a3700_spi->byte_len = len;
}

static int a3700_spi_fifo_flush(struct a3700_spi *a3700_spi)
{
        int timeout = A3700_SPI_TIMEOUT;
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        val |= A3700_SPI_FIFO_FLUSH;
        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);

        while (--timeout) {
                val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
                if (!(val & A3700_SPI_FIFO_FLUSH))
                        return 0;
                udelay(1);
        }

        return -ETIMEDOUT;
}

static int a3700_spi_init(struct a3700_spi *a3700_spi)
{
        struct spi_master *master = a3700_spi->master;
        u32 val;
        int i, ret = 0;

        /* Reset SPI unit */
        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        val |= A3700_SPI_SRST;
        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);

        udelay(A3700_SPI_TIMEOUT);

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        val &= ~A3700_SPI_SRST;
        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);

        /* Disable AUTO_CS and deactivate all chip-selects */
        a3700_spi_auto_cs_unset(a3700_spi);
        for (i = 0; i < master->num_chipselect; i++)
                a3700_spi_deactivate_cs(a3700_spi, i);

        /* Enable FIFO mode */
        a3700_spi_fifo_mode_set(a3700_spi, true);

        /* Set SPI mode */
        a3700_spi_mode_set(a3700_spi, master->mode_bits);

        /* Reset counters */
        spireg_write(a3700_spi, A3700_SPI_IF_HDR_CNT_REG, 0);
        spireg_write(a3700_spi, A3700_SPI_IF_DIN_CNT_REG, 0);

        /* Mask the interrupts and clear cause bits */
        spireg_write(a3700_spi, A3700_SPI_INT_MASK_REG, 0);
        spireg_write(a3700_spi, A3700_SPI_INT_STAT_REG, ~0U);

        return ret;
}

static irqreturn_t a3700_spi_interrupt(int irq, void *dev_id)
{
        struct spi_master *master = dev_id;
        struct a3700_spi *a3700_spi;
        u32 cause;

        a3700_spi = spi_master_get_devdata(master);

        /* Get interrupt causes */
        cause = spireg_read(a3700_spi, A3700_SPI_INT_STAT_REG);

        if (!cause || !(a3700_spi->wait_mask & cause))
                return IRQ_NONE;

        /* mask and acknowledge the SPI interrupts */
        spireg_write(a3700_spi, A3700_SPI_INT_MASK_REG, 0);
        spireg_write(a3700_spi, A3700_SPI_INT_STAT_REG, cause);

        /* Wake up the transfer */
        complete(&a3700_spi->done);

        return IRQ_HANDLED;
}

static bool a3700_spi_wait_completion(struct spi_device *spi)
{
        struct a3700_spi *a3700_spi;
        unsigned int timeout;
        unsigned int ctrl_reg;
        unsigned long timeout_jiffies;

        a3700_spi = spi_master_get_devdata(spi->master);

        /* SPI interrupt is edge-triggered, which means an interrupt will
         * be generated only when detecting a specific status bit changed
         * from '0' to '1'. So when we start waiting for a interrupt, we
         * need to check status bit in control reg first, if it is already 1,
         * then we do not need to wait for interrupt
         */
        ctrl_reg = spireg_read(a3700_spi, A3700_SPI_IF_CTRL_REG);
        if (a3700_spi->wait_mask & ctrl_reg)
                return true;

        reinit_completion(&a3700_spi->done);

        spireg_write(a3700_spi, A3700_SPI_INT_MASK_REG,
                     a3700_spi->wait_mask);

        timeout_jiffies = msecs_to_jiffies(A3700_SPI_TIMEOUT);
        timeout = wait_for_completion_timeout(&a3700_spi->done,
                                              timeout_jiffies);

        a3700_spi->wait_mask = 0;

        if (timeout)
                return true;

        /* there might be the case that right after we checked the
         * status bits in this routine and before start to wait for
         * interrupt by wait_for_completion_timeout, the interrupt
         * happens, to avoid missing it we need to double check
         * status bits in control reg, if it is already 1, then
         * consider that we have the interrupt successfully and
         * return true.
         */
        ctrl_reg = spireg_read(a3700_spi, A3700_SPI_IF_CTRL_REG);
        if (a3700_spi->wait_mask & ctrl_reg)
                return true;

        spireg_write(a3700_spi, A3700_SPI_INT_MASK_REG, 0);

        /* Timeout was reached */
        return false;
}

static bool a3700_spi_transfer_wait(struct spi_device *spi,
                                    unsigned int bit_mask)
{
        struct a3700_spi *a3700_spi;

        a3700_spi = spi_master_get_devdata(spi->master);
        a3700_spi->wait_mask = bit_mask;

        return a3700_spi_wait_completion(spi);
}

static void a3700_spi_fifo_thres_set(struct a3700_spi *a3700_spi,
                                     unsigned int bytes)
{
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        val &= ~(A3700_SPI_FIFO_THRS_MASK << A3700_SPI_RFIFO_THRS_BIT);
        val |= (bytes - 1) << A3700_SPI_RFIFO_THRS_BIT;
        val &= ~(A3700_SPI_FIFO_THRS_MASK << A3700_SPI_WFIFO_THRS_BIT);
        val |= (7 - bytes) << A3700_SPI_WFIFO_THRS_BIT;
        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);
}

static void a3700_spi_transfer_setup(struct spi_device *spi,
                                     struct spi_transfer *xfer)
{
        struct a3700_spi *a3700_spi;

        a3700_spi = spi_master_get_devdata(spi->master);

        a3700_spi_clock_set(a3700_spi, xfer->speed_hz);

        /* Use 4 bytes long transfers. Each transfer method has its way to deal
         * with the remaining bytes for non 4-bytes aligned transfers.
         */
        a3700_spi_bytelen_set(a3700_spi, 4);

        /* Initialize the working buffers */
        a3700_spi->tx_buf  = xfer->tx_buf;
        a3700_spi->rx_buf  = xfer->rx_buf;
        a3700_spi->buf_len = xfer->len;
}

static void a3700_spi_set_cs(struct spi_device *spi, bool enable)
{
        struct a3700_spi *a3700_spi = spi_master_get_devdata(spi->master);

        if (!enable)
                a3700_spi_activate_cs(a3700_spi, spi->chip_select);
        else
                a3700_spi_deactivate_cs(a3700_spi, spi->chip_select);
}

static void a3700_spi_header_set(struct a3700_spi *a3700_spi)
{
        unsigned int addr_cnt;
        u32 val = 0;

        /* Clear the header registers */
        spireg_write(a3700_spi, A3700_SPI_IF_INST_REG, 0);
        spireg_write(a3700_spi, A3700_SPI_IF_ADDR_REG, 0);
        spireg_write(a3700_spi, A3700_SPI_IF_RMODE_REG, 0);
        spireg_write(a3700_spi, A3700_SPI_IF_HDR_CNT_REG, 0);

        /* Set header counters */
        if (a3700_spi->tx_buf) {
                /*
                 * when tx data is not 4 bytes aligned, there will be unexpected
                 * bytes out of SPI output register, since it always shifts out
                 * as whole 4 bytes. This might cause incorrect transaction with
                 * some devices. To avoid that, use SPI header count feature to
                 * transfer up to 3 bytes of data first, and then make the rest
                 * of data 4-byte aligned.
                 */
                addr_cnt = a3700_spi->buf_len % 4;
                if (addr_cnt) {
                        val = (addr_cnt & A3700_SPI_ADDR_CNT_MASK)
                                << A3700_SPI_ADDR_CNT_BIT;
                        spireg_write(a3700_spi, A3700_SPI_IF_HDR_CNT_REG, val);

                        /* Update the buffer length to be transferred */
                        a3700_spi->buf_len -= addr_cnt;

                        /* transfer 1~3 bytes through address count */
                        val = 0;
                        while (addr_cnt--) {
                                val = (val << 8) | a3700_spi->tx_buf[0];
                                a3700_spi->tx_buf++;
                        }
                        spireg_write(a3700_spi, A3700_SPI_IF_ADDR_REG, val);
                }
        }
}

static int a3700_is_wfifo_full(struct a3700_spi *a3700_spi)
{
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CTRL_REG);
        return (val & A3700_SPI_WFIFO_FULL);
}

static int a3700_spi_fifo_write(struct a3700_spi *a3700_spi)
{
        u32 val;

        while (!a3700_is_wfifo_full(a3700_spi) && a3700_spi->buf_len) {
                val = *(u32 *)a3700_spi->tx_buf;
                spireg_write(a3700_spi, A3700_SPI_DATA_OUT_REG, val);
                a3700_spi->buf_len -= 4;
                a3700_spi->tx_buf += 4;
        }

        return 0;
}

static int a3700_is_rfifo_empty(struct a3700_spi *a3700_spi)
{
        u32 val = spireg_read(a3700_spi, A3700_SPI_IF_CTRL_REG);

        return (val & A3700_SPI_RFIFO_EMPTY);
}

static int a3700_spi_fifo_read(struct a3700_spi *a3700_spi)
{
        u32 val;

        while (!a3700_is_rfifo_empty(a3700_spi) && a3700_spi->buf_len) {
                val = spireg_read(a3700_spi, A3700_SPI_DATA_IN_REG);
                if (a3700_spi->buf_len >= 4) {

                        memcpy(a3700_spi->rx_buf, &val, 4);

                        a3700_spi->buf_len -= 4;
                        a3700_spi->rx_buf += 4;
                } else {
                        /*
                         * When remain bytes is not larger than 4, we should
                         * avoid memory overwriting and just write the left rx
                         * buffer bytes.
                         */
                        while (a3700_spi->buf_len) {
                                *a3700_spi->rx_buf = val & 0xff;
                                val >>= 8;

                                a3700_spi->buf_len--;
                                a3700_spi->rx_buf++;
                        }
                }
        }

        return 0;
}

static void a3700_spi_transfer_abort_fifo(struct a3700_spi *a3700_spi)
{
        int timeout = A3700_SPI_TIMEOUT;
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        val |= A3700_SPI_XFER_STOP;
        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);

        while (--timeout) {
                val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
                if (!(val & A3700_SPI_XFER_START))
                        break;
                udelay(1);
        }

        a3700_spi_fifo_flush(a3700_spi);

        val &= ~A3700_SPI_XFER_STOP;
        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);
}

static int a3700_spi_prepare_message(struct spi_master *master,
                                     struct spi_message *message)
{
        struct a3700_spi *a3700_spi = spi_master_get_devdata(master);
        struct spi_device *spi = message->spi;
        int ret;

        ret = clk_enable(a3700_spi->clk);
        if (ret) {
                dev_err(&spi->dev, "failed to enable clk with error %d\n", ret);
                return ret;
        }

        /* Flush the FIFOs */
        ret = a3700_spi_fifo_flush(a3700_spi);
        if (ret)
                return ret;

        a3700_spi_mode_set(a3700_spi, spi->mode);

        return 0;
}

static int a3700_spi_transfer_one_fifo(struct spi_master *master,
                                  struct spi_device *spi,
                                  struct spi_transfer *xfer)
{
        struct a3700_spi *a3700_spi = spi_master_get_devdata(master);
        int ret = 0, timeout = A3700_SPI_TIMEOUT;
        unsigned int nbits = 0, byte_len;
        u32 val;

        /* Make sure we use FIFO mode */
        a3700_spi_fifo_mode_set(a3700_spi, true);

        /* Configure FIFO thresholds */
        byte_len = xfer->bits_per_word >> 3;
        a3700_spi_fifo_thres_set(a3700_spi, byte_len);

        if (xfer->tx_buf)
                nbits = xfer->tx_nbits;
        else if (xfer->rx_buf)
                nbits = xfer->rx_nbits;

        a3700_spi_pin_mode_set(a3700_spi, nbits, xfer->rx_buf ? true : false);

        /* Flush the FIFOs */
        a3700_spi_fifo_flush(a3700_spi);

        /* Transfer first bytes of data when buffer is not 4-byte aligned */
        a3700_spi_header_set(a3700_spi);

        if (xfer->rx_buf) {
                /* Clear WFIFO, since it's last 2 bytes are shifted out during
                 * a read operation
                 */
                spireg_write(a3700_spi, A3700_SPI_DATA_OUT_REG, 0);

                /* Set read data length */
                spireg_write(a3700_spi, A3700_SPI_IF_DIN_CNT_REG,
                             a3700_spi->buf_len);
                /* Start READ transfer */
                val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
                val &= ~A3700_SPI_RW_EN;
                val |= A3700_SPI_XFER_START;
                spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);
        } else if (xfer->tx_buf) {
                /* Start Write transfer */
                val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
                val |= (A3700_SPI_XFER_START | A3700_SPI_RW_EN);
                spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);

                /*
                 * If there are data to be written to the SPI device, xmit_data
                 * flag is set true; otherwise the instruction in SPI_INSTR does
                 * not require data to be written to the SPI device, then
                 * xmit_data flag is set false.
                 */
                a3700_spi->xmit_data = (a3700_spi->buf_len != 0);
        }

        while (a3700_spi->buf_len) {
                if (a3700_spi->tx_buf) {
                        /* Wait wfifo ready */
                        if (!a3700_spi_transfer_wait(spi,
                                                     A3700_SPI_WFIFO_RDY)) {
                                dev_err(&spi->dev,
                                        "wait wfifo ready timed out\n");
                                ret = -ETIMEDOUT;
                                goto error;
                        }
                        /* Fill up the wfifo */
                        ret = a3700_spi_fifo_write(a3700_spi);
                        if (ret)
                                goto error;
                } else if (a3700_spi->rx_buf) {
                        /* Wait rfifo ready */
                        if (!a3700_spi_transfer_wait(spi,
                                                     A3700_SPI_RFIFO_RDY)) {
                                dev_err(&spi->dev,
                                        "wait rfifo ready timed out\n");
                                ret = -ETIMEDOUT;
                                goto error;
                        }
                        /* Drain out the rfifo */
                        ret = a3700_spi_fifo_read(a3700_spi);
                        if (ret)
                                goto error;
                }
        }

        /*
         * Stop a write transfer in fifo mode:
         *      - wait all the bytes in wfifo to be shifted out
         *       - set XFER_STOP bit
         *      - wait XFER_START bit clear
         *      - clear XFER_STOP bit
         * Stop a read transfer in fifo mode:
         *      - the hardware is to reset the XFER_START bit
         *         after the number of bytes indicated in DIN_CNT
         *         register
         *      - just wait XFER_START bit clear
         */
        if (a3700_spi->tx_buf) {
                if (a3700_spi->xmit_data) {
                        /*
                         * If there are data written to the SPI device, wait
                         * until SPI_WFIFO_EMPTY is 1 to wait for all data to
                         * transfer out of write FIFO.
                         */
                        if (!a3700_spi_transfer_wait(spi,
                                                     A3700_SPI_WFIFO_EMPTY)) {
                                dev_err(&spi->dev, "wait wfifo empty timed out\n");
                                return -ETIMEDOUT;
                        }
                }

                if (!a3700_spi_transfer_wait(spi, A3700_SPI_XFER_RDY)) {
                        dev_err(&spi->dev, "wait xfer ready timed out\n");
                        return -ETIMEDOUT;
                }

                val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
                val |= A3700_SPI_XFER_STOP;
                spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);
        }

        while (--timeout) {
                val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
                if (!(val & A3700_SPI_XFER_START))
                        break;
                udelay(1);
        }

        if (timeout == 0) {
                dev_err(&spi->dev, "wait transfer start clear timed out\n");
                ret = -ETIMEDOUT;
                goto error;
        }

        val &= ~A3700_SPI_XFER_STOP;
        spireg_write(a3700_spi, A3700_SPI_IF_CFG_REG, val);
        goto out;

error:
        a3700_spi_transfer_abort_fifo(a3700_spi);
out:
        spi_finalize_current_transfer(master);

        return ret;
}

static int a3700_spi_transfer_one_full_duplex(struct spi_master *master,
                                  struct spi_device *spi,
                                  struct spi_transfer *xfer)
{
        struct a3700_spi *a3700_spi = spi_master_get_devdata(master);
        u32 val;

        /* Disable FIFO mode */
        a3700_spi_fifo_mode_set(a3700_spi, false);

        while (a3700_spi->buf_len) {

                /* When we have less than 4 bytes to transfer, switch to 1 byte
                 * mode. This is reset after each transfer
                 */
                if (a3700_spi->buf_len < 4)
                        a3700_spi_bytelen_set(a3700_spi, 1);

                if (a3700_spi->byte_len == 1)
                        val = *a3700_spi->tx_buf;
                else
                        val = *(u32 *)a3700_spi->tx_buf;

                spireg_write(a3700_spi, A3700_SPI_DATA_OUT_REG, val);

                /* Wait for all the data to be shifted in / out */
                while (!(spireg_read(a3700_spi, A3700_SPI_IF_CTRL_REG) &
                                A3700_SPI_XFER_DONE))
                        cpu_relax();

                val = spireg_read(a3700_spi, A3700_SPI_DATA_IN_REG);

                memcpy(a3700_spi->rx_buf, &val, a3700_spi->byte_len);

                a3700_spi->buf_len -= a3700_spi->byte_len;
                a3700_spi->tx_buf += a3700_spi->byte_len;
                a3700_spi->rx_buf += a3700_spi->byte_len;

        }

        spi_finalize_current_transfer(master);

        return 0;
}

static int a3700_spi_transfer_one(struct spi_master *master,
                                  struct spi_device *spi,
                                  struct spi_transfer *xfer)
{
        a3700_spi_transfer_setup(spi, xfer);

        if (xfer->tx_buf && xfer->rx_buf)
                return a3700_spi_transfer_one_full_duplex(master, spi, xfer);

        return a3700_spi_transfer_one_fifo(master, spi, xfer);
}

static int a3700_spi_unprepare_message(struct spi_master *master,
                                       struct spi_message *message)
{
        struct a3700_spi *a3700_spi = spi_master_get_devdata(master);

        clk_disable(a3700_spi->clk);

        return 0;
}

static const struct of_device_id a3700_spi_dt_ids[] = {
        { .compatible = "marvell,armada-3700-spi", .data = NULL },
        {},
};

MODULE_DEVICE_TABLE(of, a3700_spi_dt_ids);

static int a3700_spi_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct device_node *of_node = dev->of_node;
        struct resource *res;
        struct spi_master *master;
        struct a3700_spi *spi;
        u32 num_cs = 0;
        int irq, ret = 0;

        master = spi_alloc_master(dev, sizeof(*spi));
        if (!master) {
                dev_err(dev, "master allocation failed\n");
                ret = -ENOMEM;
                goto out;
        }

        if (of_property_read_u32(of_node, "num-cs", &num_cs)) {
                dev_err(dev, "could not find num-cs\n");
                ret = -ENXIO;
                goto error;
        }

        master->bus_num = pdev->id;
        master->dev.of_node = of_node;
        master->mode_bits = SPI_MODE_3;
        master->num_chipselect = num_cs;
        master->bits_per_word_mask = SPI_BPW_MASK(8) | SPI_BPW_MASK(32);
        master->prepare_message =  a3700_spi_prepare_message;
        master->transfer_one = a3700_spi_transfer_one;
        master->unprepare_message = a3700_spi_unprepare_message;
        master->set_cs = a3700_spi_set_cs;
        master->mode_bits |= (SPI_RX_DUAL | SPI_TX_DUAL |
                              SPI_RX_QUAD | SPI_TX_QUAD);

        platform_set_drvdata(pdev, master);

        spi = spi_master_get_devdata(master);
        memset(spi, 0, sizeof(struct a3700_spi));

        spi->master = master;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        spi->base = devm_ioremap_resource(dev, res);
        if (IS_ERR(spi->base)) {
                ret = PTR_ERR(spi->base);
                goto error;
        }

        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
                dev_err(dev, "could not get irq: %d\n", irq);
                ret = -ENXIO;
                goto error;
        }
        spi->irq = irq;

        init_completion(&spi->done);

        spi->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(spi->clk)) {
                dev_err(dev, "could not find clk: %ld\n", PTR_ERR(spi->clk));
                goto error;
        }

        ret = clk_prepare(spi->clk);
        if (ret) {
                dev_err(dev, "could not prepare clk: %d\n", ret);
                goto error;
        }

        master->max_speed_hz = min_t(unsigned long, A3700_SPI_MAX_SPEED_HZ,
                                        clk_get_rate(spi->clk));
        master->min_speed_hz = DIV_ROUND_UP(clk_get_rate(spi->clk),
                                                A3700_SPI_MAX_PRESCALE);

        ret = a3700_spi_init(spi);
        if (ret)
                goto error_clk;

        ret = devm_request_irq(dev, spi->irq, a3700_spi_interrupt, 0,
                               dev_name(dev), master);
        if (ret) {
                dev_err(dev, "could not request IRQ: %d\n", ret);
                goto error_clk;
        }

        ret = devm_spi_register_master(dev, master);
        if (ret) {
                dev_err(dev, "Failed to register master\n");
                goto error_clk;
        }

        return 0;

error_clk:
        clk_disable_unprepare(spi->clk);
error:
        spi_master_put(master);
out:
        return ret;
}

static int a3700_spi_remove(struct platform_device *pdev)
{
        struct spi_master *master = platform_get_drvdata(pdev);
        struct a3700_spi *spi = spi_master_get_devdata(master);

        clk_unprepare(spi->clk);

        return 0;
}

static struct platform_driver a3700_spi_driver = {
        .driver = {
                .name   = DRIVER_NAME,
                .of_match_table = of_match_ptr(a3700_spi_dt_ids),
        },
        .probe          = a3700_spi_probe,
        .remove         = a3700_spi_remove,
};

module_platform_driver(a3700_spi_driver);

MODULE_DESCRIPTION("Armada-3700 SPI driver");
MODULE_AUTHOR("Wilson Ding <dingwei@marvell.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" DRIVER_NAME);