// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2006 Ben Dooks
 * Copyright 2006-2009 Simtec Electronics
 *      Ben Dooks <ben@simtec.co.uk>
*/

#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/slab.h>

#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>
#include <linux/spi/s3c24xx.h>
#include <linux/spi/s3c24xx-fiq.h>
#include <linux/module.h>

#include <asm/fiq.h>

#include "spi-s3c24xx-regs.h"

/**
 * struct s3c24xx_spi_devstate - per device data
 * @hz: Last frequency calculated for @sppre field.
 * @mode: Last mode setting for the @spcon field.
 * @spcon: Value to write to the SPCON register.
 * @sppre: Value to write to the SPPRE register.
 */
struct s3c24xx_spi_devstate {
        unsigned int    hz;
        unsigned int    mode;
        u8              spcon;
        u8              sppre;
};

enum spi_fiq_mode {
        FIQ_MODE_NONE   = 0,
        FIQ_MODE_TX     = 1,
        FIQ_MODE_RX     = 2,
        FIQ_MODE_TXRX   = 3,
};

struct s3c24xx_spi {
        /* bitbang has to be first */
        struct spi_bitbang       bitbang;
        struct completion        done;

        void __iomem            *regs;
        int                      irq;
        int                      len;
        int                      count;

        struct fiq_handler       fiq_handler;
        enum spi_fiq_mode        fiq_mode;
        unsigned char            fiq_inuse;
        unsigned char            fiq_claimed;

        /* data buffers */
        const unsigned char     *tx;
        unsigned char           *rx;

        struct clk              *clk;
        struct spi_master       *master;
        struct spi_device       *curdev;
        struct device           *dev;
        struct s3c2410_spi_info *pdata;
};

#define SPCON_DEFAULT (S3C2410_SPCON_MSTR | S3C2410_SPCON_SMOD_INT)
#define SPPIN_DEFAULT (S3C2410_SPPIN_KEEP)

static inline struct s3c24xx_spi *to_hw(struct spi_device *sdev)
{
        return spi_master_get_devdata(sdev->master);
}

static void s3c24xx_spi_chipsel(struct spi_device *spi, int value)
{
        struct s3c24xx_spi_devstate *cs = spi->controller_state;
        struct s3c24xx_spi *hw = to_hw(spi);

        /* change the chipselect state and the state of the spi engine clock */

        switch (value) {
        case BITBANG_CS_INACTIVE:
                writeb(cs->spcon, hw->regs + S3C2410_SPCON);
                break;

        case BITBANG_CS_ACTIVE:
                writeb(cs->spcon | S3C2410_SPCON_ENSCK,
                       hw->regs + S3C2410_SPCON);
                break;
        }
}

static int s3c24xx_spi_update_state(struct spi_device *spi,
                                    struct spi_transfer *t)
{
        struct s3c24xx_spi *hw = to_hw(spi);
        struct s3c24xx_spi_devstate *cs = spi->controller_state;
        unsigned int hz;
        unsigned int div;
        unsigned long clk;

        hz  = t ? t->speed_hz : spi->max_speed_hz;

        if (!hz)
                hz = spi->max_speed_hz;

        if (spi->mode != cs->mode) {
                u8 spcon = SPCON_DEFAULT | S3C2410_SPCON_ENSCK;

                if (spi->mode & SPI_CPHA)
                        spcon |= S3C2410_SPCON_CPHA_FMTB;

                if (spi->mode & SPI_CPOL)
                        spcon |= S3C2410_SPCON_CPOL_HIGH;

                cs->mode = spi->mode;
                cs->spcon = spcon;
        }

        if (cs->hz != hz) {
                clk = clk_get_rate(hw->clk);
                div = DIV_ROUND_UP(clk, hz * 2) - 1;

                if (div > 255)
                        div = 255;

                dev_dbg(&spi->dev, "pre-scaler=%d (wanted %d, got %ld)\n",
                        div, hz, clk / (2 * (div + 1)));

                cs->hz = hz;
                cs->sppre = div;
        }

        return 0;
}

static int s3c24xx_spi_setupxfer(struct spi_device *spi,
                                 struct spi_transfer *t)
{
        struct s3c24xx_spi_devstate *cs = spi->controller_state;
        struct s3c24xx_spi *hw = to_hw(spi);
        int ret;

        ret = s3c24xx_spi_update_state(spi, t);
        if (!ret)
                writeb(cs->sppre, hw->regs + S3C2410_SPPRE);

        return ret;
}

static int s3c24xx_spi_setup(struct spi_device *spi)
{
        struct s3c24xx_spi_devstate *cs = spi->controller_state;
        struct s3c24xx_spi *hw = to_hw(spi);
        int ret;

        /* allocate settings on the first call */
        if (!cs) {
                cs = devm_kzalloc(&spi->dev,
                                  sizeof(struct s3c24xx_spi_devstate),
                                  GFP_KERNEL);
                if (!cs)
                        return -ENOMEM;

                cs->spcon = SPCON_DEFAULT;
                cs->hz = -1;
                spi->controller_state = cs;
        }

        /* initialise the state from the device */
        ret = s3c24xx_spi_update_state(spi, NULL);
        if (ret)
                return ret;

        mutex_lock(&hw->bitbang.lock);
        if (!hw->bitbang.busy) {
                hw->bitbang.chipselect(spi, BITBANG_CS_INACTIVE);
                /* need to ndelay for 0.5 clocktick ? */
        }
        mutex_unlock(&hw->bitbang.lock);

        return 0;
}

static inline unsigned int hw_txbyte(struct s3c24xx_spi *hw, int count)
{
        return hw->tx ? hw->tx[count] : 0;
}

#ifdef CONFIG_SPI_S3C24XX_FIQ
/* Support for FIQ based pseudo-DMA to improve the transfer speed.
 *
 * This code uses the assembly helper in spi_s3c24xx_spi.S which is
 * used by the FIQ core to move data between main memory and the peripheral
 * block. Since this is code running on the processor, there is no problem
 * with cache coherency of the buffers, so we can use any buffer we like.
 */

/**
 * struct spi_fiq_code - FIQ code and header
 * @length: The length of the code fragment, excluding this header.
 * @ack_offset: The offset from @data to the word to place the IRQ ACK bit at.
 * @data: The code itself to install as a FIQ handler.
 */
struct spi_fiq_code {
        u32     length;
        u32     ack_offset;
        u8      data[];
};

/**
 * s3c24xx_spi_tryfiq - attempt to claim and setup FIQ for transfer
 * @hw: The hardware state.
 *
 * Claim the FIQ handler (only one can be active at any one time) and
 * then setup the correct transfer code for this transfer.
 *
 * This call updates all the necessary state information if successful,
 * so the caller does not need to do anything more than start the transfer
 * as normal, since the IRQ will have been re-routed to the FIQ handler.
*/
static void s3c24xx_spi_tryfiq(struct s3c24xx_spi *hw)
{
        struct pt_regs regs;
        enum spi_fiq_mode mode;
        struct spi_fiq_code *code;
        u32 *ack_ptr = NULL;
        int ret;

        if (!hw->fiq_claimed) {
                /* try and claim fiq if we haven't got it, and if not
                 * then return and simply use another transfer method */

                ret = claim_fiq(&hw->fiq_handler);
                if (ret)
                        return;
        }

        if (hw->tx && !hw->rx)
                mode = FIQ_MODE_TX;
        else if (hw->rx && !hw->tx)
                mode = FIQ_MODE_RX;
        else
                mode = FIQ_MODE_TXRX;

        regs.uregs[fiq_rspi] = (long)hw->regs;
        regs.uregs[fiq_rrx]  = (long)hw->rx;
        regs.uregs[fiq_rtx]  = (long)hw->tx + 1;
        regs.uregs[fiq_rcount] = hw->len - 1;

        set_fiq_regs(&regs);

        if (hw->fiq_mode != mode) {
                hw->fiq_mode = mode;

                switch (mode) {
                case FIQ_MODE_TX:
                        code = &s3c24xx_spi_fiq_tx;
                        break;
                case FIQ_MODE_RX:
                        code = &s3c24xx_spi_fiq_rx;
                        break;
                case FIQ_MODE_TXRX:
                        code = &s3c24xx_spi_fiq_txrx;
                        break;
                default:
                        code = NULL;
                }

                BUG_ON(!code);

                ack_ptr = (u32 *)&code->data[code->ack_offset];
                set_fiq_handler(&code->data, code->length);
        }

        s3c24xx_set_fiq(hw->irq, ack_ptr, true);

        hw->fiq_mode = mode;
        hw->fiq_inuse = 1;
}

/**
 * s3c24xx_spi_fiqop - FIQ core code callback
 * @pw: Data registered with the handler
 * @release: Whether this is a release or a return.
 *
 * Called by the FIQ code when another module wants to use the FIQ, so
 * return whether we are currently using this or not and then update our
 * internal state.
 */
static int s3c24xx_spi_fiqop(void *pw, int release)
{
        struct s3c24xx_spi *hw = pw;
        int ret = 0;

        if (release) {
                if (hw->fiq_inuse)
                        ret = -EBUSY;

                /* note, we do not need to unroute the FIQ, as the FIQ
                 * vector code de-routes it to signal the end of transfer */

                hw->fiq_mode = FIQ_MODE_NONE;
                hw->fiq_claimed = 0;
        } else {
                hw->fiq_claimed = 1;
        }

        return ret;
}

/**
 * s3c24xx_spi_initfiq - setup the information for the FIQ core
 * @hw: The hardware state.
 *
 * Setup the fiq_handler block to pass to the FIQ core.
 */
static inline void s3c24xx_spi_initfiq(struct s3c24xx_spi *hw)
{
        hw->fiq_handler.dev_id = hw;
        hw->fiq_handler.name = dev_name(hw->dev);
        hw->fiq_handler.fiq_op = s3c24xx_spi_fiqop;
}

/**
 * s3c24xx_spi_usefiq - return if we should be using FIQ.
 * @hw: The hardware state.
 *
 * Return true if the platform data specifies whether this channel is
 * allowed to use the FIQ.
 */
static inline bool s3c24xx_spi_usefiq(struct s3c24xx_spi *hw)
{
        return hw->pdata->use_fiq;
}

/**
 * s3c24xx_spi_usingfiq - return if channel is using FIQ
 * @spi: The hardware state.
 *
 * Return whether the channel is currently using the FIQ (separate from
 * whether the FIQ is claimed).
 */
static inline bool s3c24xx_spi_usingfiq(struct s3c24xx_spi *spi)
{
        return spi->fiq_inuse;
}
#else

static inline void s3c24xx_spi_initfiq(struct s3c24xx_spi *s) { }
static inline void s3c24xx_spi_tryfiq(struct s3c24xx_spi *s) { }
static inline bool s3c24xx_spi_usefiq(struct s3c24xx_spi *s) { return false; }
static inline bool s3c24xx_spi_usingfiq(struct s3c24xx_spi *s) { return false; }

#endif /* CONFIG_SPI_S3C24XX_FIQ */

static int s3c24xx_spi_txrx(struct spi_device *spi, struct spi_transfer *t)
{
        struct s3c24xx_spi *hw = to_hw(spi);

        hw->tx = t->tx_buf;
        hw->rx = t->rx_buf;
        hw->len = t->len;
        hw->count = 0;

        init_completion(&hw->done);

        hw->fiq_inuse = 0;
        if (s3c24xx_spi_usefiq(hw) && t->len >= 3)
                s3c24xx_spi_tryfiq(hw);

        /* send the first byte */
        writeb(hw_txbyte(hw, 0), hw->regs + S3C2410_SPTDAT);

        wait_for_completion(&hw->done);
        return hw->count;
}

static irqreturn_t s3c24xx_spi_irq(int irq, void *dev)
{
        struct s3c24xx_spi *hw = dev;
        unsigned int spsta = readb(hw->regs + S3C2410_SPSTA);
        unsigned int count = hw->count;

        if (spsta & S3C2410_SPSTA_DCOL) {
                dev_dbg(hw->dev, "data-collision\n");
                complete(&hw->done);
                goto irq_done;
        }

        if (!(spsta & S3C2410_SPSTA_READY)) {
                dev_dbg(hw->dev, "spi not ready for tx?\n");
                complete(&hw->done);
                goto irq_done;
        }

        if (!s3c24xx_spi_usingfiq(hw)) {
                hw->count++;

                if (hw->rx)
                        hw->rx[count] = readb(hw->regs + S3C2410_SPRDAT);

                count++;

                if (count < hw->len)
                        writeb(hw_txbyte(hw, count), hw->regs + S3C2410_SPTDAT);
                else
                        complete(&hw->done);
        } else {
                hw->count = hw->len;
                hw->fiq_inuse = 0;

                if (hw->rx)
                        hw->rx[hw->len-1] = readb(hw->regs + S3C2410_SPRDAT);

                complete(&hw->done);
        }

 irq_done:
        return IRQ_HANDLED;
}

static void s3c24xx_spi_initialsetup(struct s3c24xx_spi *hw)
{
        /* for the moment, permanently enable the clock */

        clk_enable(hw->clk);

        /* program defaults into the registers */

        writeb(0xff, hw->regs + S3C2410_SPPRE);
        writeb(SPPIN_DEFAULT, hw->regs + S3C2410_SPPIN);
        writeb(SPCON_DEFAULT, hw->regs + S3C2410_SPCON);
}

static int s3c24xx_spi_probe(struct platform_device *pdev)
{
        struct s3c2410_spi_info *pdata;
        struct s3c24xx_spi *hw;
        struct spi_master *master;
        int err = 0;

        master = spi_alloc_master(&pdev->dev, sizeof(struct s3c24xx_spi));
        if (master == NULL) {
                dev_err(&pdev->dev, "No memory for spi_master\n");
                return -ENOMEM;
        }

        hw = spi_master_get_devdata(master);

        hw->master = master;
        hw->pdata = pdata = dev_get_platdata(&pdev->dev);
        hw->dev = &pdev->dev;

        if (pdata == NULL) {
                dev_err(&pdev->dev, "No platform data supplied\n");
                err = -ENOENT;
                goto err_no_pdata;
        }

        platform_set_drvdata(pdev, hw);
        init_completion(&hw->done);

        /* initialise fiq handler */

        s3c24xx_spi_initfiq(hw);

        /* setup the master state. */

        /* the spi->mode bits understood by this driver: */
        master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;

        master->num_chipselect = hw->pdata->num_cs;
        master->bus_num = pdata->bus_num;
        master->bits_per_word_mask = SPI_BPW_MASK(8);
        /* we need to call the local chipselect callback */
        master->flags = SPI_MASTER_GPIO_SS;
        master->use_gpio_descriptors = true;

        /* setup the state for the bitbang driver */

        hw->bitbang.master         = hw->master;
        hw->bitbang.setup_transfer = s3c24xx_spi_setupxfer;
        hw->bitbang.chipselect     = s3c24xx_spi_chipsel;
        hw->bitbang.txrx_bufs      = s3c24xx_spi_txrx;

        hw->master->setup  = s3c24xx_spi_setup;

        dev_dbg(hw->dev, "bitbang at %p\n", &hw->bitbang);

        /* find and map our resources */
        hw->regs = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(hw->regs)) {
                err = PTR_ERR(hw->regs);
                goto err_no_pdata;
        }

        hw->irq = platform_get_irq(pdev, 0);
        if (hw->irq < 0) {
                err = -ENOENT;
                goto err_no_pdata;
        }

        err = devm_request_irq(&pdev->dev, hw->irq, s3c24xx_spi_irq, 0,
                                pdev->name, hw);
        if (err) {
                dev_err(&pdev->dev, "Cannot claim IRQ\n");
                goto err_no_pdata;
        }

        hw->clk = devm_clk_get(&pdev->dev, "spi");
        if (IS_ERR(hw->clk)) {
                dev_err(&pdev->dev, "No clock for device\n");
                err = PTR_ERR(hw->clk);
                goto err_no_pdata;
        }

        s3c24xx_spi_initialsetup(hw);

        /* register our spi controller */

        err = spi_bitbang_start(&hw->bitbang);
        if (err) {
                dev_err(&pdev->dev, "Failed to register SPI master\n");
                goto err_register;
        }

        return 0;

 err_register:
        clk_disable(hw->clk);

 err_no_pdata:
        spi_master_put(hw->master);
        return err;
}

static int s3c24xx_spi_remove(struct platform_device *dev)
{
        struct s3c24xx_spi *hw = platform_get_drvdata(dev);

        spi_bitbang_stop(&hw->bitbang);
        clk_disable(hw->clk);
        spi_master_put(hw->master);
        return 0;
}


#ifdef CONFIG_PM

static int s3c24xx_spi_suspend(struct device *dev)
{
        struct s3c24xx_spi *hw = dev_get_drvdata(dev);
        int ret;

        ret = spi_master_suspend(hw->master);
        if (ret)
                return ret;

        clk_disable(hw->clk);
        return 0;
}

static int s3c24xx_spi_resume(struct device *dev)
{
        struct s3c24xx_spi *hw = dev_get_drvdata(dev);

        s3c24xx_spi_initialsetup(hw);
        return spi_master_resume(hw->master);
}

static const struct dev_pm_ops s3c24xx_spi_pmops = {
        .suspend        = s3c24xx_spi_suspend,
        .resume         = s3c24xx_spi_resume,
};

#define S3C24XX_SPI_PMOPS &s3c24xx_spi_pmops
#else
#define S3C24XX_SPI_PMOPS NULL
#endif /* CONFIG_PM */

MODULE_ALIAS("platform:s3c2410-spi");
static struct platform_driver s3c24xx_spi_driver = {
        .probe          = s3c24xx_spi_probe,
        .remove         = s3c24xx_spi_remove,
        .driver         = {
                .name   = "s3c2410-spi",
                .pm     = S3C24XX_SPI_PMOPS,
        },
};
module_platform_driver(s3c24xx_spi_driver);

MODULE_DESCRIPTION("S3C24XX SPI Driver");
MODULE_AUTHOR("Ben Dooks, <ben@simtec.co.uk>");
MODULE_LICENSE("GPL");