/*
 *  Copyright (c) 2008-2014 STMicroelectronics Limited
 *
 *  Author: Angus Clark <Angus.Clark@st.com>
 *          Patrice Chotard <patrice.chotard@st.com>
 *          Lee Jones <lee.jones@linaro.org>
 *
 *  SPI master mode controller driver, used in STMicroelectronics devices.
 *
 *  May be copied or modified under the terms of the GNU General Public
 *  License Version 2.0 only.  See linux/COPYING for more information.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/pinctrl/consumer.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/of_irq.h>
#include <linux/pm_runtime.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>

/* SSC registers */
#define SSC_BRG                         0x000
#define SSC_TBUF                        0x004
#define SSC_RBUF                        0x008
#define SSC_CTL                         0x00C
#define SSC_IEN                         0x010
#define SSC_I2C                         0x018

/* SSC Control */
#define SSC_CTL_DATA_WIDTH_9            0x8
#define SSC_CTL_DATA_WIDTH_MSK          0xf
#define SSC_CTL_BM                      0xf
#define SSC_CTL_HB                      BIT(4)
#define SSC_CTL_PH                      BIT(5)
#define SSC_CTL_PO                      BIT(6)
#define SSC_CTL_SR                      BIT(7)
#define SSC_CTL_MS                      BIT(8)
#define SSC_CTL_EN                      BIT(9)
#define SSC_CTL_LPB                     BIT(10)
#define SSC_CTL_EN_TX_FIFO              BIT(11)
#define SSC_CTL_EN_RX_FIFO              BIT(12)
#define SSC_CTL_EN_CLST_RX              BIT(13)

/* SSC Interrupt Enable */
#define SSC_IEN_TEEN                    BIT(2)

#define FIFO_SIZE                       8

struct spi_st {
        /* SSC SPI Controller */
        void __iomem            *base;
        struct clk              *clk;
        struct device           *dev;

        /* SSC SPI current transaction */
        const u8                *tx_ptr;
        u8                      *rx_ptr;
        u16                     bytes_per_word;
        unsigned int            words_remaining;
        unsigned int            baud;
        struct completion       done;
};

/* Load the TX FIFO */
static void ssc_write_tx_fifo(struct spi_st *spi_st)
{
        unsigned int count, i;
        uint32_t word = 0;

        if (spi_st->words_remaining > FIFO_SIZE)
                count = FIFO_SIZE;
        else
                count = spi_st->words_remaining;

        for (i = 0; i < count; i++) {
                if (spi_st->tx_ptr) {
                        if (spi_st->bytes_per_word == 1) {
                                word = *spi_st->tx_ptr++;
                        } else {
                                word = *spi_st->tx_ptr++;
                                word = *spi_st->tx_ptr++ | (word << 8);
                        }
                }
                writel_relaxed(word, spi_st->base + SSC_TBUF);
        }
}

/* Read the RX FIFO */
static void ssc_read_rx_fifo(struct spi_st *spi_st)
{
        unsigned int count, i;
        uint32_t word = 0;

        if (spi_st->words_remaining > FIFO_SIZE)
                count = FIFO_SIZE;
        else
                count = spi_st->words_remaining;

        for (i = 0; i < count; i++) {
                word = readl_relaxed(spi_st->base + SSC_RBUF);

                if (spi_st->rx_ptr) {
                        if (spi_st->bytes_per_word == 1) {
                                *spi_st->rx_ptr++ = (uint8_t)word;
                        } else {
                                *spi_st->rx_ptr++ = (word >> 8);
                                *spi_st->rx_ptr++ = word & 0xff;
                        }
                }
        }
        spi_st->words_remaining -= count;
}

static int spi_st_transfer_one(struct spi_master *master,
                               struct spi_device *spi, struct spi_transfer *t)
{
        struct spi_st *spi_st = spi_master_get_devdata(master);
        uint32_t ctl = 0;

        /* Setup transfer */
        spi_st->tx_ptr = t->tx_buf;
        spi_st->rx_ptr = t->rx_buf;

        if (spi->bits_per_word > 8) {
                /*
                 * Anything greater than 8 bits-per-word requires 2
                 * bytes-per-word in the RX/TX buffers
                 */
                spi_st->bytes_per_word = 2;
                spi_st->words_remaining = t->len / 2;

        } else if (spi->bits_per_word == 8 && !(t->len & 0x1)) {
                /*
                 * If transfer is even-length, and 8 bits-per-word, then
                 * implement as half-length 16 bits-per-word transfer
                 */
                spi_st->bytes_per_word = 2;
                spi_st->words_remaining = t->len / 2;

                /* Set SSC_CTL to 16 bits-per-word */
                ctl = readl_relaxed(spi_st->base + SSC_CTL);
                writel_relaxed((ctl | 0xf), spi_st->base + SSC_CTL);

                readl_relaxed(spi_st->base + SSC_RBUF);

        } else {
                spi_st->bytes_per_word = 1;
                spi_st->words_remaining = t->len;
        }

        reinit_completion(&spi_st->done);

        /* Start transfer by writing to the TX FIFO */
        ssc_write_tx_fifo(spi_st);
        writel_relaxed(SSC_IEN_TEEN, spi_st->base + SSC_IEN);

        /* Wait for transfer to complete */
        wait_for_completion(&spi_st->done);

        /* Restore SSC_CTL if necessary */
        if (ctl)
                writel_relaxed(ctl, spi_st->base + SSC_CTL);

        spi_finalize_current_transfer(spi->master);

        return t->len;
}

static void spi_st_cleanup(struct spi_device *spi)
{
        gpio_free(spi->cs_gpio);
}

/* the spi->mode bits understood by this driver: */
#define MODEBITS  (SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST | SPI_LOOP | SPI_CS_HIGH)
static int spi_st_setup(struct spi_device *spi)
{
        struct spi_st *spi_st = spi_master_get_devdata(spi->master);
        u32 spi_st_clk, sscbrg, var;
        u32 hz = spi->max_speed_hz;
        int cs = spi->cs_gpio;
        int ret;

        if (!hz)  {
                dev_err(&spi->dev, "max_speed_hz unspecified\n");
                return -EINVAL;
        }

        if (!gpio_is_valid(cs)) {
                dev_err(&spi->dev, "%d is not a valid gpio\n", cs);
                return -EINVAL;
        }

        ret = gpio_request(cs, dev_name(&spi->dev));
        if (ret) {
                dev_err(&spi->dev, "could not request gpio:%d\n", cs);
                return ret;
        }

        ret = gpio_direction_output(cs, spi->mode & SPI_CS_HIGH);
        if (ret)
                goto out_free_gpio;

        spi_st_clk = clk_get_rate(spi_st->clk);

        /* Set SSC_BRF */
        sscbrg = spi_st_clk / (2 * hz);
        if (sscbrg < 0x07 || sscbrg > BIT(16)) {
                dev_err(&spi->dev,
                        "baudrate %d outside valid range %d\n", sscbrg, hz);
                ret = -EINVAL;
                goto out_free_gpio;
        }

        spi_st->baud = spi_st_clk / (2 * sscbrg);
        if (sscbrg == BIT(16)) /* 16-bit counter wraps */
                sscbrg = 0x0;

        writel_relaxed(sscbrg, spi_st->base + SSC_BRG);

        dev_dbg(&spi->dev,
                "setting baudrate:target= %u hz, actual= %u hz, sscbrg= %u\n",
                hz, spi_st->baud, sscbrg);

        /* Set SSC_CTL and enable SSC */
        var = readl_relaxed(spi_st->base + SSC_CTL);
        var |= SSC_CTL_MS;

        if (spi->mode & SPI_CPOL)
                var |= SSC_CTL_PO;
        else
                var &= ~SSC_CTL_PO;

        if (spi->mode & SPI_CPHA)
                var |= SSC_CTL_PH;
        else
                var &= ~SSC_CTL_PH;

        if ((spi->mode & SPI_LSB_FIRST) == 0)
                var |= SSC_CTL_HB;
        else
                var &= ~SSC_CTL_HB;

        if (spi->mode & SPI_LOOP)
                var |= SSC_CTL_LPB;
        else
                var &= ~SSC_CTL_LPB;

        var &= ~SSC_CTL_DATA_WIDTH_MSK;
        var |= (spi->bits_per_word - 1);

        var |= SSC_CTL_EN_TX_FIFO | SSC_CTL_EN_RX_FIFO;
        var |= SSC_CTL_EN;

        writel_relaxed(var, spi_st->base + SSC_CTL);

        /* Clear the status register */
        readl_relaxed(spi_st->base + SSC_RBUF);

        return 0;

out_free_gpio:
        gpio_free(cs);
        return ret;
}

/* Interrupt fired when TX shift register becomes empty */
static irqreturn_t spi_st_irq(int irq, void *dev_id)
{
        struct spi_st *spi_st = (struct spi_st *)dev_id;

        /* Read RX FIFO */
        ssc_read_rx_fifo(spi_st);

        /* Fill TX FIFO */
        if (spi_st->words_remaining) {
                ssc_write_tx_fifo(spi_st);
        } else {
                /* TX/RX complete */
                writel_relaxed(0x0, spi_st->base + SSC_IEN);
                /*
                 * read SSC_IEN to ensure that this bit is set
                 * before re-enabling interrupt
                 */
                readl(spi_st->base + SSC_IEN);
                complete(&spi_st->done);
        }

        return IRQ_HANDLED;
}

static int spi_st_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct spi_master *master;
        struct resource *res;
        struct spi_st *spi_st;
        int irq, ret = 0;
        u32 var;

        master = spi_alloc_master(&pdev->dev, sizeof(*spi_st));
        if (!master)
                return -ENOMEM;

        master->dev.of_node             = np;
        master->mode_bits               = MODEBITS;
        master->setup                   = spi_st_setup;
        master->cleanup                 = spi_st_cleanup;
        master->transfer_one            = spi_st_transfer_one;
        master->bits_per_word_mask      = SPI_BPW_MASK(8) | SPI_BPW_MASK(16);
        master->auto_runtime_pm         = true;
        master->bus_num                 = pdev->id;
        spi_st                          = spi_master_get_devdata(master);

        spi_st->clk = devm_clk_get(&pdev->dev, "ssc");
        if (IS_ERR(spi_st->clk)) {
                dev_err(&pdev->dev, "Unable to request clock\n");
                ret = PTR_ERR(spi_st->clk);
                goto put_master;
        }

        ret = clk_prepare_enable(spi_st->clk);
        if (ret)
                goto put_master;

        init_completion(&spi_st->done);

        /* Get resources */
        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        spi_st->base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(spi_st->base)) {
                ret = PTR_ERR(spi_st->base);
                goto clk_disable;
        }

        /* Disable I2C and Reset SSC */
        writel_relaxed(0x0, spi_st->base + SSC_I2C);
        var = readw_relaxed(spi_st->base + SSC_CTL);
        var |= SSC_CTL_SR;
        writel_relaxed(var, spi_st->base + SSC_CTL);

        udelay(1);
        var = readl_relaxed(spi_st->base + SSC_CTL);
        var &= ~SSC_CTL_SR;
        writel_relaxed(var, spi_st->base + SSC_CTL);

        /* Set SSC into slave mode before reconfiguring PIO pins */
        var = readl_relaxed(spi_st->base + SSC_CTL);
        var &= ~SSC_CTL_MS;
        writel_relaxed(var, spi_st->base + SSC_CTL);

        irq = irq_of_parse_and_map(np, 0);
        if (!irq) {
                dev_err(&pdev->dev, "IRQ missing or invalid\n");
                ret = -EINVAL;
                goto clk_disable;
        }

        ret = devm_request_irq(&pdev->dev, irq, spi_st_irq, 0,
                               pdev->name, spi_st);
        if (ret) {
                dev_err(&pdev->dev, "Failed to request irq %d\n", irq);
                goto clk_disable;
        }

        /* by default the device is on */
        pm_runtime_set_active(&pdev->dev);
        pm_runtime_enable(&pdev->dev);

        platform_set_drvdata(pdev, master);

        ret = devm_spi_register_master(&pdev->dev, master);
        if (ret) {
                dev_err(&pdev->dev, "Failed to register master\n");
                goto clk_disable;
        }

        return 0;

clk_disable:
        clk_disable_unprepare(spi_st->clk);
put_master:
        spi_master_put(master);
        return ret;
}

static int spi_st_remove(struct platform_device *pdev)
{
        struct spi_master *master = platform_get_drvdata(pdev);
        struct spi_st *spi_st = spi_master_get_devdata(master);

        clk_disable_unprepare(spi_st->clk);

        pinctrl_pm_select_sleep_state(&pdev->dev);

        return 0;
}

#ifdef CONFIG_PM
static int spi_st_runtime_suspend(struct device *dev)
{
        struct spi_master *master = dev_get_drvdata(dev);
        struct spi_st *spi_st = spi_master_get_devdata(master);

        writel_relaxed(0, spi_st->base + SSC_IEN);
        pinctrl_pm_select_sleep_state(dev);

        clk_disable_unprepare(spi_st->clk);

        return 0;
}

static int spi_st_runtime_resume(struct device *dev)
{
        struct spi_master *master = dev_get_drvdata(dev);
        struct spi_st *spi_st = spi_master_get_devdata(master);
        int ret;

        ret = clk_prepare_enable(spi_st->clk);
        pinctrl_pm_select_default_state(dev);

        return ret;
}
#endif

#ifdef CONFIG_PM_SLEEP
static int spi_st_suspend(struct device *dev)
{
        struct spi_master *master = dev_get_drvdata(dev);
        int ret;

        ret = spi_master_suspend(master);
        if (ret)
                return ret;

        return pm_runtime_force_suspend(dev);
}

static int spi_st_resume(struct device *dev)
{
        struct spi_master *master = dev_get_drvdata(dev);
        int ret;

        ret = spi_master_resume(master);
        if (ret)
                return ret;

        return pm_runtime_force_resume(dev);
}
#endif

static const struct dev_pm_ops spi_st_pm = {
        SET_SYSTEM_SLEEP_PM_OPS(spi_st_suspend, spi_st_resume)
        SET_RUNTIME_PM_OPS(spi_st_runtime_suspend, spi_st_runtime_resume, NULL)
};

static const struct of_device_id stm_spi_match[] = {
        { .compatible = "st,comms-ssc4-spi", },
        {},
};
MODULE_DEVICE_TABLE(of, stm_spi_match);

static struct platform_driver spi_st_driver = {
        .driver = {
                .name = "spi-st",
                .pm = &spi_st_pm,
                .of_match_table = of_match_ptr(stm_spi_match),
        },
        .probe = spi_st_probe,
        .remove = spi_st_remove,
};
module_platform_driver(spi_st_driver);

MODULE_AUTHOR("Patrice Chotard <patrice.chotard@st.com>");
MODULE_DESCRIPTION("STM SSC SPI driver");
MODULE_LICENSE("GPL v2");