Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[mirror_ubuntu-zesty-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_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_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)

/* Flags and macros for struct a3700_spi */
#define A3700_INSTR_CNT                 1
#define A3700_ADDR_CNT                  3
#define A3700_DUMMY_CNT                 1

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;
        u32 addr_cnt;
        u32 instr_cnt;
        size_t hdr_cnt;
};

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)
{
        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 1:
                break;
        case 2:
                val |= A3700_SPI_DATA_PIN0;
                break;
        case 4:
                val |= A3700_SPI_DATA_PIN1;
                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)
{
        u32 val;

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        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, u16 mode)
{
        u32 val;
        u32 prescale;

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

        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);
        }

        val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
        val &= ~(A3700_SPI_CLK_POL | A3700_SPI_CLK_PHA);

        if (mode & SPI_CPOL)
                val |= A3700_SPI_CLK_POL;

        if (mode & SPI_CPHA)
                val |= A3700_SPI_CLK_PHA;

        spireg_write(a3700_spi, A3700_SPI_IF_CFG_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);

        /* 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 */
        if (a3700_spi->wait_mask & cause)
                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);

        return true;
}

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;
        unsigned int byte_len;

        a3700_spi = spi_master_get_devdata(spi->master);

        a3700_spi_clock_set(a3700_spi, xfer->speed_hz, spi->mode);

        byte_len = xfer->bits_per_word >> 3;

        a3700_spi_fifo_thres_set(a3700_spi, byte_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)
{
        u32 instr_cnt = 0, addr_cnt = 0, dummy_cnt = 0;
        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);

        /* Set header counters */
        if (a3700_spi->tx_buf) {
                if (a3700_spi->buf_len <= a3700_spi->instr_cnt) {
                        instr_cnt = a3700_spi->buf_len;
                } else if (a3700_spi->buf_len <= (a3700_spi->instr_cnt +
                                                  a3700_spi->addr_cnt)) {
                        instr_cnt = a3700_spi->instr_cnt;
                        addr_cnt = a3700_spi->buf_len - instr_cnt;
                } else if (a3700_spi->buf_len <= a3700_spi->hdr_cnt) {
                        instr_cnt = a3700_spi->instr_cnt;
                        addr_cnt = a3700_spi->addr_cnt;
                        /* Need to handle the normal write case with 1 byte
                         * data
                         */
                        if (!a3700_spi->tx_buf[instr_cnt + addr_cnt])
                                dummy_cnt = a3700_spi->buf_len - instr_cnt -
                                            addr_cnt;
                }
                val |= ((instr_cnt & A3700_SPI_INSTR_CNT_MASK)
                        << A3700_SPI_INSTR_CNT_BIT);
                val |= ((addr_cnt & A3700_SPI_ADDR_CNT_MASK)
                        << A3700_SPI_ADDR_CNT_BIT);
                val |= ((dummy_cnt & A3700_SPI_DUMMY_CNT_MASK)
                        << A3700_SPI_DUMMY_CNT_BIT);
        }
        spireg_write(a3700_spi, A3700_SPI_IF_HDR_CNT_REG, val);

        /* Update the buffer length to be transferred */
        a3700_spi->buf_len -= (instr_cnt + addr_cnt + dummy_cnt);

        /* Set Instruction */
        val = 0;
        while (instr_cnt--) {
                val = (val << 8) | a3700_spi->tx_buf[0];
                a3700_spi->tx_buf++;
        }
        spireg_write(a3700_spi, A3700_SPI_IF_INST_REG, val);

        /* Set Address */
        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;
        int i = 0;

        while (!a3700_is_wfifo_full(a3700_spi) && a3700_spi->buf_len) {
                val = 0;
                if (a3700_spi->buf_len >= 4) {
                        val = cpu_to_le32(*(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;
                } else {
                        /*
                         * If the remained buffer length is less than 4-bytes,
                         * we should pad the write buffer with all ones. So that
                         * it avoids overwrite the unexpected bytes following
                         * the last one.
                         */
                        val = GENMASK(31, 0);
                        while (a3700_spi->buf_len) {
                                val &= ~(0xff << (8 * i));
                                val |= *a3700_spi->tx_buf++ << (8 * i);
                                i++;
                                a3700_spi->buf_len--;

                                spireg_write(a3700_spi, A3700_SPI_DATA_OUT_REG,
                                             val);
                        }
                        break;
                }
        }

        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) {
                        u32 data = le32_to_cpu(val);
                        memcpy(a3700_spi->rx_buf, &data, 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_bytelen_set(a3700_spi, 4);

        return 0;
}

static int a3700_spi_transfer_one(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;
        u32 val;

        a3700_spi_transfer_setup(spi, xfer);

        a3700_spi->tx_buf  = xfer->tx_buf;
        a3700_spi->rx_buf  = xfer->rx_buf;
        a3700_spi->buf_len = xfer->len;

        /* SPI transfer headers */
        a3700_spi_header_set(a3700_spi);

        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);

        if (xfer->rx_buf) {
                /* 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;
                        }
                } else {
                        /*
                         * If the instruction in SPI_INSTR does not require data
                         * to be written to the SPI device, wait until SPI_RDY
                         * is 1 for the SPI interface to be in idle.
                         */
                        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_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->flags = SPI_MASTER_HALF_DUPLEX;
        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;
        spi->instr_cnt = A3700_INSTR_CNT;
        spi->addr_cnt = A3700_ADDR_CNT;
        spi->hdr_cnt = A3700_INSTR_CNT + A3700_ADDR_CNT +
                       A3700_DUMMY_CNT;

        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;
        }

        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);
        spi_master_put(master);

        return 0;
}

static struct platform_driver a3700_spi_driver = {
        .driver = {
                .name   = DRIVER_NAME,
                .owner  = THIS_MODULE,
                .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);