/*
 * Freescale MXS SPI master driver
 *
 * Copyright 2012 DENX Software Engineering, GmbH.
 * Copyright 2012 Freescale Semiconductor, Inc.
 * Copyright 2008 Embedded Alley Solutions, Inc All Rights Reserved.
 *
 * Rework and transition to new API by:
 * Marek Vasut <marex@denx.de>
 *
 * Based on previous attempt by:
 * Fabio Estevam <fabio.estevam@freescale.com>
 *
 * Based on code from U-Boot bootloader by:
 * Marek Vasut <marex@denx.de>
 *
 * Based on spi-stmp.c, which is:
 * Author: Dmitry Pervushin <dimka@embeddedalley.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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 */

#include <linux/kernel.h>
#include <linux/ioport.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_gpio.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/highmem.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/completion.h>
#include <linux/gpio.h>
#include <linux/regulator/consumer.h>
#include <linux/module.h>
#include <linux/stmp_device.h>
#include <linux/spi/spi.h>
#include <linux/spi/mxs-spi.h>

#define DRIVER_NAME             "mxs-spi"

/* Use 10S timeout for very long transfers, it should suffice. */
#define SSP_TIMEOUT             10000

#define SG_MAXLEN               0xff00

/*
 * Flags for txrx functions.  More efficient that using an argument register for
 * each one.
 */
#define TXRX_WRITE              (1<<0)  /* This is a write */
#define TXRX_DEASSERT_CS        (1<<1)  /* De-assert CS at end of txrx */

struct mxs_spi {
        struct mxs_ssp          ssp;
        struct completion       c;
        unsigned int            sck;    /* Rate requested (vs actual) */
};

static int mxs_spi_setup_transfer(struct spi_device *dev,
                                  const struct spi_transfer *t)
{
        struct mxs_spi *spi = spi_master_get_devdata(dev->master);
        struct mxs_ssp *ssp = &spi->ssp;
        const unsigned int hz = min(dev->max_speed_hz, t->speed_hz);

        if (hz == 0) {
                dev_err(&dev->dev, "SPI clock rate of zero not allowed\n");
                return -EINVAL;
        }

        if (hz != spi->sck) {
                mxs_ssp_set_clk_rate(ssp, hz);
                /*
                 * Save requested rate, hz, rather than the actual rate,
                 * ssp->clk_rate.  Otherwise we would set the rate every transfer
                 * when the actual rate is not quite the same as requested rate.
                 */
                spi->sck = hz;
                /*
                 * Perhaps we should return an error if the actual clock is
                 * nowhere close to what was requested?
                 */
        }

        writel(BM_SSP_CTRL0_LOCK_CS,
                ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET);

        writel(BF_SSP_CTRL1_SSP_MODE(BV_SSP_CTRL1_SSP_MODE__SPI) |
               BF_SSP_CTRL1_WORD_LENGTH(BV_SSP_CTRL1_WORD_LENGTH__EIGHT_BITS) |
               ((dev->mode & SPI_CPOL) ? BM_SSP_CTRL1_POLARITY : 0) |
               ((dev->mode & SPI_CPHA) ? BM_SSP_CTRL1_PHASE : 0),
               ssp->base + HW_SSP_CTRL1(ssp));

        writel(0x0, ssp->base + HW_SSP_CMD0);
        writel(0x0, ssp->base + HW_SSP_CMD1);

        return 0;
}

static u32 mxs_spi_cs_to_reg(unsigned cs)
{
        u32 select = 0;

        /*
         * i.MX28 Datasheet: 17.10.1: HW_SSP_CTRL0
         *
         * The bits BM_SSP_CTRL0_WAIT_FOR_CMD and BM_SSP_CTRL0_WAIT_FOR_IRQ
         * in HW_SSP_CTRL0 register do have multiple usage, please refer to
         * the datasheet for further details. In SPI mode, they are used to
         * toggle the chip-select lines (nCS pins).
         */
        if (cs & 1)
                select |= BM_SSP_CTRL0_WAIT_FOR_CMD;
        if (cs & 2)
                select |= BM_SSP_CTRL0_WAIT_FOR_IRQ;

        return select;
}

static int mxs_ssp_wait(struct mxs_spi *spi, int offset, int mask, bool set)
{
        const unsigned long timeout = jiffies + msecs_to_jiffies(SSP_TIMEOUT);
        struct mxs_ssp *ssp = &spi->ssp;
        u32 reg;

        do {
                reg = readl_relaxed(ssp->base + offset);

                if (!set)
                        reg = ~reg;

                reg &= mask;

                if (reg == mask)
                        return 0;
        } while (time_before(jiffies, timeout));

        return -ETIMEDOUT;
}

static void mxs_ssp_dma_irq_callback(void *param)
{
        struct mxs_spi *spi = param;

        complete(&spi->c);
}

static irqreturn_t mxs_ssp_irq_handler(int irq, void *dev_id)
{
        struct mxs_ssp *ssp = dev_id;

        dev_err(ssp->dev, "%s[%i] CTRL1=%08x STATUS=%08x\n",
                __func__, __LINE__,
                readl(ssp->base + HW_SSP_CTRL1(ssp)),
                readl(ssp->base + HW_SSP_STATUS(ssp)));
        return IRQ_HANDLED;
}

static int mxs_spi_txrx_dma(struct mxs_spi *spi,
                            unsigned char *buf, int len,
                            unsigned int flags)
{
        struct mxs_ssp *ssp = &spi->ssp;
        struct dma_async_tx_descriptor *desc = NULL;
        const bool vmalloced_buf = is_vmalloc_addr(buf);
        const int desc_len = vmalloced_buf ? PAGE_SIZE : SG_MAXLEN;
        const int sgs = DIV_ROUND_UP(len, desc_len);
        int sg_count;
        int min, ret;
        u32 ctrl0;
        struct page *vm_page;
        struct {
                u32                     pio[4];
                struct scatterlist      sg;
        } *dma_xfer;

        if (!len)
                return -EINVAL;

        dma_xfer = kcalloc(sgs, sizeof(*dma_xfer), GFP_KERNEL);
        if (!dma_xfer)
                return -ENOMEM;

        reinit_completion(&spi->c);

        /* Chip select was already programmed into CTRL0 */
        ctrl0 = readl(ssp->base + HW_SSP_CTRL0);
        ctrl0 &= ~(BM_SSP_CTRL0_XFER_COUNT | BM_SSP_CTRL0_IGNORE_CRC |
                 BM_SSP_CTRL0_READ);
        ctrl0 |= BM_SSP_CTRL0_DATA_XFER;

        if (!(flags & TXRX_WRITE))
                ctrl0 |= BM_SSP_CTRL0_READ;

        /* Queue the DMA data transfer. */
        for (sg_count = 0; sg_count < sgs; sg_count++) {
                /* Prepare the transfer descriptor. */
                min = min(len, desc_len);

                /*
                 * De-assert CS on last segment if flag is set (i.e., no more
                 * transfers will follow)
                 */
                if ((sg_count + 1 == sgs) && (flags & TXRX_DEASSERT_CS))
                        ctrl0 |= BM_SSP_CTRL0_IGNORE_CRC;

                if (ssp->devid == IMX23_SSP) {
                        ctrl0 &= ~BM_SSP_CTRL0_XFER_COUNT;
                        ctrl0 |= min;
                }

                dma_xfer[sg_count].pio[0] = ctrl0;
                dma_xfer[sg_count].pio[3] = min;

                if (vmalloced_buf) {
                        vm_page = vmalloc_to_page(buf);
                        if (!vm_page) {
                                ret = -ENOMEM;
                                goto err_vmalloc;
                        }

                        sg_init_table(&dma_xfer[sg_count].sg, 1);
                        sg_set_page(&dma_xfer[sg_count].sg, vm_page,
                                    min, offset_in_page(buf));
                } else {
                        sg_init_one(&dma_xfer[sg_count].sg, buf, min);
                }

                ret = dma_map_sg(ssp->dev, &dma_xfer[sg_count].sg, 1,
                        (flags & TXRX_WRITE) ? DMA_TO_DEVICE : DMA_FROM_DEVICE);

                len -= min;
                buf += min;

                /* Queue the PIO register write transfer. */
                desc = dmaengine_prep_slave_sg(ssp->dmach,
                                (struct scatterlist *)dma_xfer[sg_count].pio,
                                (ssp->devid == IMX23_SSP) ? 1 : 4,
                                DMA_TRANS_NONE,
                                sg_count ? DMA_PREP_INTERRUPT : 0);
                if (!desc) {
                        dev_err(ssp->dev,
                                "Failed to get PIO reg. write descriptor.\n");
                        ret = -EINVAL;
                        goto err_mapped;
                }

                desc = dmaengine_prep_slave_sg(ssp->dmach,
                                &dma_xfer[sg_count].sg, 1,
                                (flags & TXRX_WRITE) ? DMA_MEM_TO_DEV : DMA_DEV_TO_MEM,
                                DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

                if (!desc) {
                        dev_err(ssp->dev,
                                "Failed to get DMA data write descriptor.\n");
                        ret = -EINVAL;
                        goto err_mapped;
                }
        }

        /*
         * The last descriptor must have this callback,
         * to finish the DMA transaction.
         */
        desc->callback = mxs_ssp_dma_irq_callback;
        desc->callback_param = spi;

        /* Start the transfer. */
        dmaengine_submit(desc);
        dma_async_issue_pending(ssp->dmach);

        if (!wait_for_completion_timeout(&spi->c,
                                         msecs_to_jiffies(SSP_TIMEOUT))) {
                dev_err(ssp->dev, "DMA transfer timeout\n");
                ret = -ETIMEDOUT;
                dmaengine_terminate_all(ssp->dmach);
                goto err_vmalloc;
        }

        ret = 0;

err_vmalloc:
        while (--sg_count >= 0) {
err_mapped:
                dma_unmap_sg(ssp->dev, &dma_xfer[sg_count].sg, 1,
                        (flags & TXRX_WRITE) ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
        }

        kfree(dma_xfer);

        return ret;
}

static int mxs_spi_txrx_pio(struct mxs_spi *spi,
                            unsigned char *buf, int len,
                            unsigned int flags)
{
        struct mxs_ssp *ssp = &spi->ssp;

        writel(BM_SSP_CTRL0_IGNORE_CRC,
               ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_CLR);

        while (len--) {
                if (len == 0 && (flags & TXRX_DEASSERT_CS))
                        writel(BM_SSP_CTRL0_IGNORE_CRC,
                               ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET);

                if (ssp->devid == IMX23_SSP) {
                        writel(BM_SSP_CTRL0_XFER_COUNT,
                                ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_CLR);
                        writel(1,
                                ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET);
                } else {
                        writel(1, ssp->base + HW_SSP_XFER_SIZE);
                }

                if (flags & TXRX_WRITE)
                        writel(BM_SSP_CTRL0_READ,
                                ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_CLR);
                else
                        writel(BM_SSP_CTRL0_READ,
                                ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET);

                writel(BM_SSP_CTRL0_RUN,
                                ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET);

                if (mxs_ssp_wait(spi, HW_SSP_CTRL0, BM_SSP_CTRL0_RUN, 1))
                        return -ETIMEDOUT;

                if (flags & TXRX_WRITE)
                        writel(*buf, ssp->base + HW_SSP_DATA(ssp));

                writel(BM_SSP_CTRL0_DATA_XFER,
                             ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET);

                if (!(flags & TXRX_WRITE)) {
                        if (mxs_ssp_wait(spi, HW_SSP_STATUS(ssp),
                                                BM_SSP_STATUS_FIFO_EMPTY, 0))
                                return -ETIMEDOUT;

                        *buf = (readl(ssp->base + HW_SSP_DATA(ssp)) & 0xff);
                }

                if (mxs_ssp_wait(spi, HW_SSP_CTRL0, BM_SSP_CTRL0_RUN, 0))
                        return -ETIMEDOUT;

                buf++;
        }

        if (len <= 0)
                return 0;

        return -ETIMEDOUT;
}

static int mxs_spi_transfer_one(struct spi_master *master,
                                struct spi_message *m)
{
        struct mxs_spi *spi = spi_master_get_devdata(master);
        struct mxs_ssp *ssp = &spi->ssp;
        struct spi_transfer *t;
        unsigned int flag;
        int status = 0;

        /* Program CS register bits here, it will be used for all transfers. */
        writel(BM_SSP_CTRL0_WAIT_FOR_CMD | BM_SSP_CTRL0_WAIT_FOR_IRQ,
               ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_CLR);
        writel(mxs_spi_cs_to_reg(m->spi->chip_select),
               ssp->base + HW_SSP_CTRL0 + STMP_OFFSET_REG_SET);

        list_for_each_entry(t, &m->transfers, transfer_list) {

                status = mxs_spi_setup_transfer(m->spi, t);
                if (status)
                        break;

                /* De-assert on last transfer, inverted by cs_change flag */
                flag = (&t->transfer_list == m->transfers.prev) ^ t->cs_change ?
                       TXRX_DEASSERT_CS : 0;

                /*
                 * Small blocks can be transfered via PIO.
                 * Measured by empiric means:
                 *
                 * dd if=/dev/mtdblock0 of=/dev/null bs=1024k count=1
                 *
                 * DMA only: 2.164808 seconds, 473.0KB/s
                 * Combined: 1.676276 seconds, 610.9KB/s
                 */
                if (t->len < 32) {
                        writel(BM_SSP_CTRL1_DMA_ENABLE,
                                ssp->base + HW_SSP_CTRL1(ssp) +
                                STMP_OFFSET_REG_CLR);

                        if (t->tx_buf)
                                status = mxs_spi_txrx_pio(spi,
                                                (void *)t->tx_buf,
                                                t->len, flag | TXRX_WRITE);
                        if (t->rx_buf)
                                status = mxs_spi_txrx_pio(spi,
                                                t->rx_buf, t->len,
                                                flag);
                } else {
                        writel(BM_SSP_CTRL1_DMA_ENABLE,
                                ssp->base + HW_SSP_CTRL1(ssp) +
                                STMP_OFFSET_REG_SET);

                        if (t->tx_buf)
                                status = mxs_spi_txrx_dma(spi,
                                                (void *)t->tx_buf, t->len,
                                                flag | TXRX_WRITE);
                        if (t->rx_buf)
                                status = mxs_spi_txrx_dma(spi,
                                                t->rx_buf, t->len,
                                                flag);
                }

                if (status) {
                        stmp_reset_block(ssp->base);
                        break;
                }

                m->actual_length += t->len;
        }

        m->status = status;
        spi_finalize_current_message(master);

        return status;
}

static const struct of_device_id mxs_spi_dt_ids[] = {
        { .compatible = "fsl,imx23-spi", .data = (void *) IMX23_SSP, },
        { .compatible = "fsl,imx28-spi", .data = (void *) IMX28_SSP, },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, mxs_spi_dt_ids);

static int mxs_spi_probe(struct platform_device *pdev)
{
        const struct of_device_id *of_id =
                        of_match_device(mxs_spi_dt_ids, &pdev->dev);
        struct device_node *np = pdev->dev.of_node;
        struct spi_master *master;
        struct mxs_spi *spi;
        struct mxs_ssp *ssp;
        struct resource *iores;
        struct clk *clk;
        void __iomem *base;
        int devid, clk_freq;
        int ret = 0, irq_err;

        /*
         * Default clock speed for the SPI core. 160MHz seems to
         * work reasonably well with most SPI flashes, so use this
         * as a default. Override with "clock-frequency" DT prop.
         */
        const int clk_freq_default = 160000000;

        iores = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        irq_err = platform_get_irq(pdev, 0);
        if (irq_err < 0)
                return irq_err;

        base = devm_ioremap_resource(&pdev->dev, iores);
        if (IS_ERR(base))
                return PTR_ERR(base);

        clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(clk))
                return PTR_ERR(clk);

        devid = (enum mxs_ssp_id) of_id->data;
        ret = of_property_read_u32(np, "clock-frequency",
                                   &clk_freq);
        if (ret)
                clk_freq = clk_freq_default;

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

        master->transfer_one_message = mxs_spi_transfer_one;
        master->bits_per_word_mask = SPI_BPW_MASK(8);
        master->mode_bits = SPI_CPOL | SPI_CPHA;
        master->num_chipselect = 3;
        master->dev.of_node = np;
        master->flags = SPI_MASTER_HALF_DUPLEX;

        spi = spi_master_get_devdata(master);
        ssp = &spi->ssp;
        ssp->dev = &pdev->dev;
        ssp->clk = clk;
        ssp->base = base;
        ssp->devid = devid;

        init_completion(&spi->c);

        ret = devm_request_irq(&pdev->dev, irq_err, mxs_ssp_irq_handler, 0,
                               dev_name(&pdev->dev), ssp);
        if (ret)
                goto out_master_free;

        ssp->dmach = dma_request_slave_channel(&pdev->dev, "rx-tx");
        if (!ssp->dmach) {
                dev_err(ssp->dev, "Failed to request DMA\n");
                ret = -ENODEV;
                goto out_master_free;
        }

        ret = clk_prepare_enable(ssp->clk);
        if (ret)
                goto out_dma_release;

        clk_set_rate(ssp->clk, clk_freq);

        ret = stmp_reset_block(ssp->base);
        if (ret)
                goto out_disable_clk;

        platform_set_drvdata(pdev, master);

        ret = devm_spi_register_master(&pdev->dev, master);
        if (ret) {
                dev_err(&pdev->dev, "Cannot register SPI master, %d\n", ret);
                goto out_disable_clk;
        }

        return 0;

out_disable_clk:
        clk_disable_unprepare(ssp->clk);
out_dma_release:
        dma_release_channel(ssp->dmach);
out_master_free:
        spi_master_put(master);
        return ret;
}

static int mxs_spi_remove(struct platform_device *pdev)
{
        struct spi_master *master;
        struct mxs_spi *spi;
        struct mxs_ssp *ssp;

        master = platform_get_drvdata(pdev);
        spi = spi_master_get_devdata(master);
        ssp = &spi->ssp;

        clk_disable_unprepare(ssp->clk);
        dma_release_channel(ssp->dmach);

        return 0;
}

static struct platform_driver mxs_spi_driver = {
        .probe  = mxs_spi_probe,
        .remove = mxs_spi_remove,
        .driver = {
                .name   = DRIVER_NAME,
                .of_match_table = mxs_spi_dt_ids,
        },
};

module_platform_driver(mxs_spi_driver);

MODULE_AUTHOR("Marek Vasut <marex@denx.de>");
MODULE_DESCRIPTION("MXS SPI master driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:mxs-spi");