/*
 * Copyright (C) 2012 - 2014 Allwinner Tech
 * Pan Nan <pannan@allwinnertech.com>
 *
 * Copyright (C) 2014 Maxime Ripard
 * Maxime Ripard <maxime.ripard@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 as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>

#include <linux/spi/spi.h>

#define SUN4I_FIFO_DEPTH                64

#define SUN4I_RXDATA_REG                0x00

#define SUN4I_TXDATA_REG                0x04

#define SUN4I_CTL_REG                   0x08
#define SUN4I_CTL_ENABLE                        BIT(0)
#define SUN4I_CTL_MASTER                        BIT(1)
#define SUN4I_CTL_CPHA                          BIT(2)
#define SUN4I_CTL_CPOL                          BIT(3)
#define SUN4I_CTL_CS_ACTIVE_LOW                 BIT(4)
#define SUN4I_CTL_LMTF                          BIT(6)
#define SUN4I_CTL_TF_RST                        BIT(8)
#define SUN4I_CTL_RF_RST                        BIT(9)
#define SUN4I_CTL_XCH                           BIT(10)
#define SUN4I_CTL_CS_MASK                       0x3000
#define SUN4I_CTL_CS(cs)                        (((cs) << 12) & SUN4I_CTL_CS_MASK)
#define SUN4I_CTL_DHB                           BIT(15)
#define SUN4I_CTL_CS_MANUAL                     BIT(16)
#define SUN4I_CTL_CS_LEVEL                      BIT(17)
#define SUN4I_CTL_TP                            BIT(18)

#define SUN4I_INT_CTL_REG               0x0c
#define SUN4I_INT_CTL_RF_F34                    BIT(4)
#define SUN4I_INT_CTL_TF_E34                    BIT(12)
#define SUN4I_INT_CTL_TC                        BIT(16)

#define SUN4I_INT_STA_REG               0x10

#define SUN4I_DMA_CTL_REG               0x14

#define SUN4I_WAIT_REG                  0x18

#define SUN4I_CLK_CTL_REG               0x1c
#define SUN4I_CLK_CTL_CDR2_MASK                 0xff
#define SUN4I_CLK_CTL_CDR2(div)                 ((div) & SUN4I_CLK_CTL_CDR2_MASK)
#define SUN4I_CLK_CTL_CDR1_MASK                 0xf
#define SUN4I_CLK_CTL_CDR1(div)                 (((div) & SUN4I_CLK_CTL_CDR1_MASK) << 8)
#define SUN4I_CLK_CTL_DRS                       BIT(12)

#define SUN4I_MAX_XFER_SIZE                     0xffffff

#define SUN4I_BURST_CNT_REG             0x20
#define SUN4I_BURST_CNT(cnt)                    ((cnt) & SUN4I_MAX_XFER_SIZE)

#define SUN4I_XMIT_CNT_REG              0x24
#define SUN4I_XMIT_CNT(cnt)                     ((cnt) & SUN4I_MAX_XFER_SIZE)


#define SUN4I_FIFO_STA_REG              0x28
#define SUN4I_FIFO_STA_RF_CNT_MASK              0x7f
#define SUN4I_FIFO_STA_RF_CNT_BITS              0
#define SUN4I_FIFO_STA_TF_CNT_MASK              0x7f
#define SUN4I_FIFO_STA_TF_CNT_BITS              16

struct sun4i_spi {
        struct spi_master       *master;
        void __iomem            *base_addr;
        struct clk              *hclk;
        struct clk              *mclk;

        struct completion       done;

        const u8                *tx_buf;
        u8                      *rx_buf;
        int                     len;
};

static inline u32 sun4i_spi_read(struct sun4i_spi *sspi, u32 reg)
{
        return readl(sspi->base_addr + reg);
}

static inline void sun4i_spi_write(struct sun4i_spi *sspi, u32 reg, u32 value)
{
        writel(value, sspi->base_addr + reg);
}

static inline u32 sun4i_spi_get_tx_fifo_count(struct sun4i_spi *sspi)
{
        u32 reg = sun4i_spi_read(sspi, SUN4I_FIFO_STA_REG);

        reg >>= SUN4I_FIFO_STA_TF_CNT_BITS;

        return reg & SUN4I_FIFO_STA_TF_CNT_MASK;
}

static inline void sun4i_spi_enable_interrupt(struct sun4i_spi *sspi, u32 mask)
{
        u32 reg = sun4i_spi_read(sspi, SUN4I_INT_CTL_REG);

        reg |= mask;
        sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, reg);
}

static inline void sun4i_spi_disable_interrupt(struct sun4i_spi *sspi, u32 mask)
{
        u32 reg = sun4i_spi_read(sspi, SUN4I_INT_CTL_REG);

        reg &= ~mask;
        sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, reg);
}

static inline void sun4i_spi_drain_fifo(struct sun4i_spi *sspi, int len)
{
        u32 reg, cnt;
        u8 byte;

        /* See how much data is available */
        reg = sun4i_spi_read(sspi, SUN4I_FIFO_STA_REG);
        reg &= SUN4I_FIFO_STA_RF_CNT_MASK;
        cnt = reg >> SUN4I_FIFO_STA_RF_CNT_BITS;

        if (len > cnt)
                len = cnt;

        while (len--) {
                byte = readb(sspi->base_addr + SUN4I_RXDATA_REG);
                if (sspi->rx_buf)
                        *sspi->rx_buf++ = byte;
        }
}

static inline void sun4i_spi_fill_fifo(struct sun4i_spi *sspi, int len)
{
        u32 cnt;
        u8 byte;

        /* See how much data we can fit */
        cnt = SUN4I_FIFO_DEPTH - sun4i_spi_get_tx_fifo_count(sspi);

        len = min3(len, (int)cnt, sspi->len);

        while (len--) {
                byte = sspi->tx_buf ? *sspi->tx_buf++ : 0;
                writeb(byte, sspi->base_addr + SUN4I_TXDATA_REG);
                sspi->len--;
        }
}

static void sun4i_spi_set_cs(struct spi_device *spi, bool enable)
{
        struct sun4i_spi *sspi = spi_master_get_devdata(spi->master);
        u32 reg;

        reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);

        reg &= ~SUN4I_CTL_CS_MASK;
        reg |= SUN4I_CTL_CS(spi->chip_select);

        /* We want to control the chip select manually */
        reg |= SUN4I_CTL_CS_MANUAL;

        if (enable)
                reg |= SUN4I_CTL_CS_LEVEL;
        else
                reg &= ~SUN4I_CTL_CS_LEVEL;

        /*
         * Even though this looks irrelevant since we are supposed to
         * be controlling the chip select manually, this bit also
         * controls the levels of the chip select for inactive
         * devices.
         *
         * If we don't set it, the chip select level will go low by
         * default when the device is idle, which is not really
         * expected in the common case where the chip select is active
         * low.
         */
        if (spi->mode & SPI_CS_HIGH)
                reg &= ~SUN4I_CTL_CS_ACTIVE_LOW;
        else
                reg |= SUN4I_CTL_CS_ACTIVE_LOW;

        sun4i_spi_write(sspi, SUN4I_CTL_REG, reg);
}

static size_t sun4i_spi_max_transfer_size(struct spi_device *spi)
{
        return SUN4I_FIFO_DEPTH - 1;
}

static int sun4i_spi_transfer_one(struct spi_master *master,
                                  struct spi_device *spi,
                                  struct spi_transfer *tfr)
{
        struct sun4i_spi *sspi = spi_master_get_devdata(master);
        unsigned int mclk_rate, div, timeout;
        unsigned int start, end, tx_time;
        unsigned int tx_len = 0;
        int ret = 0;
        u32 reg;

        /* We don't support transfer larger than the FIFO */
        if (tfr->len > SUN4I_MAX_XFER_SIZE)
                return -EMSGSIZE;

        if (tfr->tx_buf && tfr->len >= SUN4I_MAX_XFER_SIZE)
                return -EMSGSIZE;

        reinit_completion(&sspi->done);
        sspi->tx_buf = tfr->tx_buf;
        sspi->rx_buf = tfr->rx_buf;
        sspi->len = tfr->len;

        /* Clear pending interrupts */
        sun4i_spi_write(sspi, SUN4I_INT_STA_REG, ~0);


        reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);

        /* Reset FIFOs */
        sun4i_spi_write(sspi, SUN4I_CTL_REG,
                        reg | SUN4I_CTL_RF_RST | SUN4I_CTL_TF_RST);

        /*
         * Setup the transfer control register: Chip Select,
         * polarities, etc.
         */
        if (spi->mode & SPI_CPOL)
                reg |= SUN4I_CTL_CPOL;
        else
                reg &= ~SUN4I_CTL_CPOL;

        if (spi->mode & SPI_CPHA)
                reg |= SUN4I_CTL_CPHA;
        else
                reg &= ~SUN4I_CTL_CPHA;

        if (spi->mode & SPI_LSB_FIRST)
                reg |= SUN4I_CTL_LMTF;
        else
                reg &= ~SUN4I_CTL_LMTF;


        /*
         * If it's a TX only transfer, we don't want to fill the RX
         * FIFO with bogus data
         */
        if (sspi->rx_buf)
                reg &= ~SUN4I_CTL_DHB;
        else
                reg |= SUN4I_CTL_DHB;

        sun4i_spi_write(sspi, SUN4I_CTL_REG, reg);

        /* Ensure that we have a parent clock fast enough */
        mclk_rate = clk_get_rate(sspi->mclk);
        if (mclk_rate < (2 * tfr->speed_hz)) {
                clk_set_rate(sspi->mclk, 2 * tfr->speed_hz);
                mclk_rate = clk_get_rate(sspi->mclk);
        }

        /*
         * Setup clock divider.
         *
         * We have two choices there. Either we can use the clock
         * divide rate 1, which is calculated thanks to this formula:
         * SPI_CLK = MOD_CLK / (2 ^ (cdr + 1))
         * Or we can use CDR2, which is calculated with the formula:
         * SPI_CLK = MOD_CLK / (2 * (cdr + 1))
         * Wether we use the former or the latter is set through the
         * DRS bit.
         *
         * First try CDR2, and if we can't reach the expected
         * frequency, fall back to CDR1.
         */
        div = mclk_rate / (2 * tfr->speed_hz);
        if (div <= (SUN4I_CLK_CTL_CDR2_MASK + 1)) {
                if (div > 0)
                        div--;

                reg = SUN4I_CLK_CTL_CDR2(div) | SUN4I_CLK_CTL_DRS;
        } else {
                div = ilog2(mclk_rate) - ilog2(tfr->speed_hz);
                reg = SUN4I_CLK_CTL_CDR1(div);
        }

        sun4i_spi_write(sspi, SUN4I_CLK_CTL_REG, reg);

        /* Setup the transfer now... */
        if (sspi->tx_buf)
                tx_len = tfr->len;

        /* Setup the counters */
        sun4i_spi_write(sspi, SUN4I_BURST_CNT_REG, SUN4I_BURST_CNT(tfr->len));
        sun4i_spi_write(sspi, SUN4I_XMIT_CNT_REG, SUN4I_XMIT_CNT(tx_len));

        /*
         * Fill the TX FIFO
         * Filling the FIFO fully causes timeout for some reason
         * at least on spi2 on A10s
         */
        sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH - 1);

        /* Enable the interrupts */
        sun4i_spi_enable_interrupt(sspi, SUN4I_INT_CTL_TC |
                                         SUN4I_INT_CTL_RF_F34);
        /* Only enable Tx FIFO interrupt if we really need it */
        if (tx_len > SUN4I_FIFO_DEPTH)
                sun4i_spi_enable_interrupt(sspi, SUN4I_INT_CTL_TF_E34);

        /* Start the transfer */
        reg = sun4i_spi_read(sspi, SUN4I_CTL_REG);
        sun4i_spi_write(sspi, SUN4I_CTL_REG, reg | SUN4I_CTL_XCH);

        tx_time = max(tfr->len * 8 * 2 / (tfr->speed_hz / 1000), 100U);
        start = jiffies;
        timeout = wait_for_completion_timeout(&sspi->done,
                                              msecs_to_jiffies(tx_time));
        end = jiffies;
        if (!timeout) {
                dev_warn(&master->dev,
                         "%s: timeout transferring %u bytes@%iHz for %i(%i)ms",
                         dev_name(&spi->dev), tfr->len, tfr->speed_hz,
                         jiffies_to_msecs(end - start), tx_time);
                ret = -ETIMEDOUT;
                goto out;
        }


out:
        sun4i_spi_write(sspi, SUN4I_INT_CTL_REG, 0);

        return ret;
}

static irqreturn_t sun4i_spi_handler(int irq, void *dev_id)
{
        struct sun4i_spi *sspi = dev_id;
        u32 status = sun4i_spi_read(sspi, SUN4I_INT_STA_REG);

        /* Transfer complete */
        if (status & SUN4I_INT_CTL_TC) {
                sun4i_spi_write(sspi, SUN4I_INT_STA_REG, SUN4I_INT_CTL_TC);
                sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH);
                complete(&sspi->done);
                return IRQ_HANDLED;
        }

        /* Receive FIFO 3/4 full */
        if (status & SUN4I_INT_CTL_RF_F34) {
                sun4i_spi_drain_fifo(sspi, SUN4I_FIFO_DEPTH);
                /* Only clear the interrupt _after_ draining the FIFO */
                sun4i_spi_write(sspi, SUN4I_INT_STA_REG, SUN4I_INT_CTL_RF_F34);
                return IRQ_HANDLED;
        }

        /* Transmit FIFO 3/4 empty */
        if (status & SUN4I_INT_CTL_TF_E34) {
                sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH);

                if (!sspi->len)
                        /* nothing left to transmit */
                        sun4i_spi_disable_interrupt(sspi, SUN4I_INT_CTL_TF_E34);

                /* Only clear the interrupt _after_ re-seeding the FIFO */
                sun4i_spi_write(sspi, SUN4I_INT_STA_REG, SUN4I_INT_CTL_TF_E34);

                return IRQ_HANDLED;
        }

        return IRQ_NONE;
}

static int sun4i_spi_runtime_resume(struct device *dev)
{
        struct spi_master *master = dev_get_drvdata(dev);
        struct sun4i_spi *sspi = spi_master_get_devdata(master);
        int ret;

        ret = clk_prepare_enable(sspi->hclk);
        if (ret) {
                dev_err(dev, "Couldn't enable AHB clock\n");
                goto out;
        }

        ret = clk_prepare_enable(sspi->mclk);
        if (ret) {
                dev_err(dev, "Couldn't enable module clock\n");
                goto err;
        }

        sun4i_spi_write(sspi, SUN4I_CTL_REG,
                        SUN4I_CTL_ENABLE | SUN4I_CTL_MASTER | SUN4I_CTL_TP);

        return 0;

err:
        clk_disable_unprepare(sspi->hclk);
out:
        return ret;
}

static int sun4i_spi_runtime_suspend(struct device *dev)
{
        struct spi_master *master = dev_get_drvdata(dev);
        struct sun4i_spi *sspi = spi_master_get_devdata(master);

        clk_disable_unprepare(sspi->mclk);
        clk_disable_unprepare(sspi->hclk);

        return 0;
}

static int sun4i_spi_probe(struct platform_device *pdev)
{
        struct spi_master *master;
        struct sun4i_spi *sspi;
        struct resource *res;
        int ret = 0, irq;

        master = spi_alloc_master(&pdev->dev, sizeof(struct sun4i_spi));
        if (!master) {
                dev_err(&pdev->dev, "Unable to allocate SPI Master\n");
                return -ENOMEM;
        }

        platform_set_drvdata(pdev, master);
        sspi = spi_master_get_devdata(master);

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        sspi->base_addr = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(sspi->base_addr)) {
                ret = PTR_ERR(sspi->base_addr);
                goto err_free_master;
        }

        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
                dev_err(&pdev->dev, "No spi IRQ specified\n");
                ret = -ENXIO;
                goto err_free_master;
        }

        ret = devm_request_irq(&pdev->dev, irq, sun4i_spi_handler,
                               0, "sun4i-spi", sspi);
        if (ret) {
                dev_err(&pdev->dev, "Cannot request IRQ\n");
                goto err_free_master;
        }

        sspi->master = master;
        master->max_speed_hz = 100 * 1000 * 1000;
        master->min_speed_hz = 3 * 1000;
        master->set_cs = sun4i_spi_set_cs;
        master->transfer_one = sun4i_spi_transfer_one;
        master->num_chipselect = 4;
        master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_LSB_FIRST;
        master->bits_per_word_mask = SPI_BPW_MASK(8);
        master->dev.of_node = pdev->dev.of_node;
        master->auto_runtime_pm = true;
        master->max_transfer_size = sun4i_spi_max_transfer_size;

        sspi->hclk = devm_clk_get(&pdev->dev, "ahb");
        if (IS_ERR(sspi->hclk)) {
                dev_err(&pdev->dev, "Unable to acquire AHB clock\n");
                ret = PTR_ERR(sspi->hclk);
                goto err_free_master;
        }

        sspi->mclk = devm_clk_get(&pdev->dev, "mod");
        if (IS_ERR(sspi->mclk)) {
                dev_err(&pdev->dev, "Unable to acquire module clock\n");
                ret = PTR_ERR(sspi->mclk);
                goto err_free_master;
        }

        init_completion(&sspi->done);

        /*
         * This wake-up/shutdown pattern is to be able to have the
         * device woken up, even if runtime_pm is disabled
         */
        ret = sun4i_spi_runtime_resume(&pdev->dev);
        if (ret) {
                dev_err(&pdev->dev, "Couldn't resume the device\n");
                goto err_free_master;
        }

        pm_runtime_set_active(&pdev->dev);
        pm_runtime_enable(&pdev->dev);
        pm_runtime_idle(&pdev->dev);

        ret = devm_spi_register_master(&pdev->dev, master);
        if (ret) {
                dev_err(&pdev->dev, "cannot register SPI master\n");
                goto err_pm_disable;
        }

        return 0;

err_pm_disable:
        pm_runtime_disable(&pdev->dev);
        sun4i_spi_runtime_suspend(&pdev->dev);
err_free_master:
        spi_master_put(master);
        return ret;
}

static int sun4i_spi_remove(struct platform_device *pdev)
{
        pm_runtime_disable(&pdev->dev);

        return 0;
}

static const struct of_device_id sun4i_spi_match[] = {
        { .compatible = "allwinner,sun4i-a10-spi", },
        {}
};
MODULE_DEVICE_TABLE(of, sun4i_spi_match);

static const struct dev_pm_ops sun4i_spi_pm_ops = {
        .runtime_resume         = sun4i_spi_runtime_resume,
        .runtime_suspend        = sun4i_spi_runtime_suspend,
};

static struct platform_driver sun4i_spi_driver = {
        .probe  = sun4i_spi_probe,
        .remove = sun4i_spi_remove,
        .driver = {
                .name           = "sun4i-spi",
                .of_match_table = sun4i_spi_match,
                .pm             = &sun4i_spi_pm_ops,
        },
};
module_platform_driver(sun4i_spi_driver);

MODULE_AUTHOR("Pan Nan <pannan@allwinnertech.com>");
MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
MODULE_DESCRIPTION("Allwinner A1X/A20 SPI controller driver");
MODULE_LICENSE("GPL");