// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2009 Texas Instruments.
 * Copyright (C) 2010 EF Johnson Technologies
 */

#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>
#include <linux/slab.h>

#include <linux/platform_data/spi-davinci.h>

#define CS_DEFAULT      0xFF

#define SPIFMT_PHASE_MASK       BIT(16)
#define SPIFMT_POLARITY_MASK    BIT(17)
#define SPIFMT_DISTIMER_MASK    BIT(18)
#define SPIFMT_SHIFTDIR_MASK    BIT(20)
#define SPIFMT_WAITENA_MASK     BIT(21)
#define SPIFMT_PARITYENA_MASK   BIT(22)
#define SPIFMT_ODD_PARITY_MASK  BIT(23)
#define SPIFMT_WDELAY_MASK      0x3f000000u
#define SPIFMT_WDELAY_SHIFT     24
#define SPIFMT_PRESCALE_SHIFT   8

/* SPIPC0 */
#define SPIPC0_DIFUN_MASK       BIT(11)         /* MISO */
#define SPIPC0_DOFUN_MASK       BIT(10)         /* MOSI */
#define SPIPC0_CLKFUN_MASK      BIT(9)          /* CLK */
#define SPIPC0_SPIENA_MASK      BIT(8)          /* nREADY */

#define SPIINT_MASKALL          0x0101035F
#define SPIINT_MASKINT          0x0000015F
#define SPI_INTLVL_1            0x000001FF
#define SPI_INTLVL_0            0x00000000

/* SPIDAT1 (upper 16 bit defines) */
#define SPIDAT1_CSHOLD_MASK     BIT(12)
#define SPIDAT1_WDEL            BIT(10)

/* SPIGCR1 */
#define SPIGCR1_CLKMOD_MASK     BIT(1)
#define SPIGCR1_MASTER_MASK     BIT(0)
#define SPIGCR1_POWERDOWN_MASK  BIT(8)
#define SPIGCR1_LOOPBACK_MASK   BIT(16)
#define SPIGCR1_SPIENA_MASK     BIT(24)

/* SPIBUF */
#define SPIBUF_TXFULL_MASK      BIT(29)
#define SPIBUF_RXEMPTY_MASK     BIT(31)

/* SPIDELAY */
#define SPIDELAY_C2TDELAY_SHIFT 24
#define SPIDELAY_C2TDELAY_MASK  (0xFF << SPIDELAY_C2TDELAY_SHIFT)
#define SPIDELAY_T2CDELAY_SHIFT 16
#define SPIDELAY_T2CDELAY_MASK  (0xFF << SPIDELAY_T2CDELAY_SHIFT)
#define SPIDELAY_T2EDELAY_SHIFT 8
#define SPIDELAY_T2EDELAY_MASK  (0xFF << SPIDELAY_T2EDELAY_SHIFT)
#define SPIDELAY_C2EDELAY_SHIFT 0
#define SPIDELAY_C2EDELAY_MASK  0xFF

/* Error Masks */
#define SPIFLG_DLEN_ERR_MASK            BIT(0)
#define SPIFLG_TIMEOUT_MASK             BIT(1)
#define SPIFLG_PARERR_MASK              BIT(2)
#define SPIFLG_DESYNC_MASK              BIT(3)
#define SPIFLG_BITERR_MASK              BIT(4)
#define SPIFLG_OVRRUN_MASK              BIT(6)
#define SPIFLG_BUF_INIT_ACTIVE_MASK     BIT(24)
#define SPIFLG_ERROR_MASK               (SPIFLG_DLEN_ERR_MASK \
                                | SPIFLG_TIMEOUT_MASK | SPIFLG_PARERR_MASK \
                                | SPIFLG_DESYNC_MASK | SPIFLG_BITERR_MASK \
                                | SPIFLG_OVRRUN_MASK)

#define SPIINT_DMA_REQ_EN       BIT(16)

/* SPI Controller registers */
#define SPIGCR0         0x00
#define SPIGCR1         0x04
#define SPIINT          0x08
#define SPILVL          0x0c
#define SPIFLG          0x10
#define SPIPC0          0x14
#define SPIDAT1         0x3c
#define SPIBUF          0x40
#define SPIDELAY        0x48
#define SPIDEF          0x4c
#define SPIFMT0         0x50

#define DMA_MIN_BYTES   16

/* SPI Controller driver's private data. */
struct davinci_spi {
        struct spi_bitbang      bitbang;
        struct clk              *clk;

        u8                      version;
        resource_size_t         pbase;
        void __iomem            *base;
        u32                     irq;
        struct completion       done;

        const void              *tx;
        void                    *rx;
        int                     rcount;
        int                     wcount;

        struct dma_chan         *dma_rx;
        struct dma_chan         *dma_tx;

        struct davinci_spi_platform_data pdata;

        void                    (*get_rx)(u32 rx_data, struct davinci_spi *);
        u32                     (*get_tx)(struct davinci_spi *);

        u8                      *bytes_per_word;

        u8                      prescaler_limit;
};

static struct davinci_spi_config davinci_spi_default_cfg;

static void davinci_spi_rx_buf_u8(u32 data, struct davinci_spi *dspi)
{
        if (dspi->rx) {
                u8 *rx = dspi->rx;
                *rx++ = (u8)data;
                dspi->rx = rx;
        }
}

static void davinci_spi_rx_buf_u16(u32 data, struct davinci_spi *dspi)
{
        if (dspi->rx) {
                u16 *rx = dspi->rx;
                *rx++ = (u16)data;
                dspi->rx = rx;
        }
}

static u32 davinci_spi_tx_buf_u8(struct davinci_spi *dspi)
{
        u32 data = 0;

        if (dspi->tx) {
                const u8 *tx = dspi->tx;

                data = *tx++;
                dspi->tx = tx;
        }
        return data;
}

static u32 davinci_spi_tx_buf_u16(struct davinci_spi *dspi)
{
        u32 data = 0;

        if (dspi->tx) {
                const u16 *tx = dspi->tx;

                data = *tx++;
                dspi->tx = tx;
        }
        return data;
}

static inline void set_io_bits(void __iomem *addr, u32 bits)
{
        u32 v = ioread32(addr);

        v |= bits;
        iowrite32(v, addr);
}

static inline void clear_io_bits(void __iomem *addr, u32 bits)
{
        u32 v = ioread32(addr);

        v &= ~bits;
        iowrite32(v, addr);
}

/*
 * Interface to control the chip select signal
 */
static void davinci_spi_chipselect(struct spi_device *spi, int value)
{
        struct davinci_spi *dspi;
        struct davinci_spi_config *spicfg = spi->controller_data;
        u8 chip_sel = spi->chip_select;
        u16 spidat1 = CS_DEFAULT;

        dspi = spi_master_get_devdata(spi->master);

        /* program delay transfers if tx_delay is non zero */
        if (spicfg && spicfg->wdelay)
                spidat1 |= SPIDAT1_WDEL;

        /*
         * Board specific chip select logic decides the polarity and cs
         * line for the controller
         */
        if (spi->cs_gpiod) {
                /*
                 * FIXME: is this code ever executed? This host does not
                 * set SPI_MASTER_GPIO_SS so this chipselect callback should
                 * not get called from the SPI core when we are using
                 * GPIOs for chip select.
                 */
                if (value == BITBANG_CS_ACTIVE)
                        gpiod_set_value(spi->cs_gpiod, 1);
                else
                        gpiod_set_value(spi->cs_gpiod, 0);
        } else {
                if (value == BITBANG_CS_ACTIVE) {
                        if (!(spi->mode & SPI_CS_WORD))
                                spidat1 |= SPIDAT1_CSHOLD_MASK;
                        spidat1 &= ~(0x1 << chip_sel);
                }
        }

        iowrite16(spidat1, dspi->base + SPIDAT1 + 2);
}

/**
 * davinci_spi_get_prescale - Calculates the correct prescale value
 * @maxspeed_hz: the maximum rate the SPI clock can run at
 *
 * This function calculates the prescale value that generates a clock rate
 * less than or equal to the specified maximum.
 *
 * Returns: calculated prescale value for easy programming into SPI registers
 * or negative error number if valid prescalar cannot be updated.
 */
static inline int davinci_spi_get_prescale(struct davinci_spi *dspi,
                                                        u32 max_speed_hz)
{
        int ret;

        /* Subtract 1 to match what will be programmed into SPI register. */
        ret = DIV_ROUND_UP(clk_get_rate(dspi->clk), max_speed_hz) - 1;

        if (ret < dspi->prescaler_limit || ret > 255)
                return -EINVAL;

        return ret;
}

/**
 * davinci_spi_setup_transfer - This functions will determine transfer method
 * @spi: spi device on which data transfer to be done
 * @t: spi transfer in which transfer info is filled
 *
 * This function determines data transfer method (8/16/32 bit transfer).
 * It will also set the SPI Clock Control register according to
 * SPI slave device freq.
 */
static int davinci_spi_setup_transfer(struct spi_device *spi,
                struct spi_transfer *t)
{

        struct davinci_spi *dspi;
        struct davinci_spi_config *spicfg;
        u8 bits_per_word = 0;
        u32 hz = 0, spifmt = 0;
        int prescale;

        dspi = spi_master_get_devdata(spi->master);
        spicfg = spi->controller_data;
        if (!spicfg)
                spicfg = &davinci_spi_default_cfg;

        if (t) {
                bits_per_word = t->bits_per_word;
                hz = t->speed_hz;
        }

        /* if bits_per_word is not set then set it default */
        if (!bits_per_word)
                bits_per_word = spi->bits_per_word;

        /*
         * Assign function pointer to appropriate transfer method
         * 8bit, 16bit or 32bit transfer
         */
        if (bits_per_word <= 8) {
                dspi->get_rx = davinci_spi_rx_buf_u8;
                dspi->get_tx = davinci_spi_tx_buf_u8;
                dspi->bytes_per_word[spi->chip_select] = 1;
        } else {
                dspi->get_rx = davinci_spi_rx_buf_u16;
                dspi->get_tx = davinci_spi_tx_buf_u16;
                dspi->bytes_per_word[spi->chip_select] = 2;
        }

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

        /* Set up SPIFMTn register, unique to this chipselect. */

        prescale = davinci_spi_get_prescale(dspi, hz);
        if (prescale < 0)
                return prescale;

        spifmt = (prescale << SPIFMT_PRESCALE_SHIFT) | (bits_per_word & 0x1f);

        if (spi->mode & SPI_LSB_FIRST)
                spifmt |= SPIFMT_SHIFTDIR_MASK;

        if (spi->mode & SPI_CPOL)
                spifmt |= SPIFMT_POLARITY_MASK;

        if (!(spi->mode & SPI_CPHA))
                spifmt |= SPIFMT_PHASE_MASK;

        /*
        * Assume wdelay is used only on SPI peripherals that has this field
        * in SPIFMTn register and when it's configured from board file or DT.
        */
        if (spicfg->wdelay)
                spifmt |= ((spicfg->wdelay << SPIFMT_WDELAY_SHIFT)
                                & SPIFMT_WDELAY_MASK);

        /*
         * Version 1 hardware supports two basic SPI modes:
         *  - Standard SPI mode uses 4 pins, with chipselect
         *  - 3 pin SPI is a 4 pin variant without CS (SPI_NO_CS)
         *      (distinct from SPI_3WIRE, with just one data wire;
         *      or similar variants without MOSI or without MISO)
         *
         * Version 2 hardware supports an optional handshaking signal,
         * so it can support two more modes:
         *  - 5 pin SPI variant is standard SPI plus SPI_READY
         *  - 4 pin with enable is (SPI_READY | SPI_NO_CS)
         */

        if (dspi->version == SPI_VERSION_2) {

                u32 delay = 0;

                if (spicfg->odd_parity)
                        spifmt |= SPIFMT_ODD_PARITY_MASK;

                if (spicfg->parity_enable)
                        spifmt |= SPIFMT_PARITYENA_MASK;

                if (spicfg->timer_disable) {
                        spifmt |= SPIFMT_DISTIMER_MASK;
                } else {
                        delay |= (spicfg->c2tdelay << SPIDELAY_C2TDELAY_SHIFT)
                                                & SPIDELAY_C2TDELAY_MASK;
                        delay |= (spicfg->t2cdelay << SPIDELAY_T2CDELAY_SHIFT)
                                                & SPIDELAY_T2CDELAY_MASK;
                }

                if (spi->mode & SPI_READY) {
                        spifmt |= SPIFMT_WAITENA_MASK;
                        delay |= (spicfg->t2edelay << SPIDELAY_T2EDELAY_SHIFT)
                                                & SPIDELAY_T2EDELAY_MASK;
                        delay |= (spicfg->c2edelay << SPIDELAY_C2EDELAY_SHIFT)
                                                & SPIDELAY_C2EDELAY_MASK;
                }

                iowrite32(delay, dspi->base + SPIDELAY);
        }

        iowrite32(spifmt, dspi->base + SPIFMT0);

        return 0;
}

static int davinci_spi_of_setup(struct spi_device *spi)
{
        struct davinci_spi_config *spicfg = spi->controller_data;
        struct device_node *np = spi->dev.of_node;
        struct davinci_spi *dspi = spi_master_get_devdata(spi->master);
        u32 prop;

        if (spicfg == NULL && np) {
                spicfg = kzalloc(sizeof(*spicfg), GFP_KERNEL);
                if (!spicfg)
                        return -ENOMEM;
                *spicfg = davinci_spi_default_cfg;
                /* override with dt configured values */
                if (!of_property_read_u32(np, "ti,spi-wdelay", &prop))
                        spicfg->wdelay = (u8)prop;
                spi->controller_data = spicfg;

                if (dspi->dma_rx && dspi->dma_tx)
                        spicfg->io_type = SPI_IO_TYPE_DMA;
        }

        return 0;
}

/**
 * davinci_spi_setup - This functions will set default transfer method
 * @spi: spi device on which data transfer to be done
 *
 * This functions sets the default transfer method.
 */
static int davinci_spi_setup(struct spi_device *spi)
{
        struct davinci_spi *dspi;
        struct device_node *np = spi->dev.of_node;
        bool internal_cs = true;

        dspi = spi_master_get_devdata(spi->master);

        if (!(spi->mode & SPI_NO_CS)) {
                if (np && spi->cs_gpiod)
                        internal_cs = false;

                if (internal_cs)
                        set_io_bits(dspi->base + SPIPC0, 1 << spi->chip_select);
        }

        if (spi->mode & SPI_READY)
                set_io_bits(dspi->base + SPIPC0, SPIPC0_SPIENA_MASK);

        if (spi->mode & SPI_LOOP)
                set_io_bits(dspi->base + SPIGCR1, SPIGCR1_LOOPBACK_MASK);
        else
                clear_io_bits(dspi->base + SPIGCR1, SPIGCR1_LOOPBACK_MASK);

        return davinci_spi_of_setup(spi);
}

static void davinci_spi_cleanup(struct spi_device *spi)
{
        struct davinci_spi_config *spicfg = spi->controller_data;

        spi->controller_data = NULL;
        if (spi->dev.of_node)
                kfree(spicfg);
}

static bool davinci_spi_can_dma(struct spi_master *master,
                                struct spi_device *spi,
                                struct spi_transfer *xfer)
{
        struct davinci_spi_config *spicfg = spi->controller_data;
        bool can_dma = false;

        if (spicfg)
                can_dma = (spicfg->io_type == SPI_IO_TYPE_DMA) &&
                        (xfer->len >= DMA_MIN_BYTES) &&
                        !is_vmalloc_addr(xfer->rx_buf) &&
                        !is_vmalloc_addr(xfer->tx_buf);

        return can_dma;
}

static int davinci_spi_check_error(struct davinci_spi *dspi, int int_status)
{
        struct device *sdev = dspi->bitbang.master->dev.parent;

        if (int_status & SPIFLG_TIMEOUT_MASK) {
                dev_err(sdev, "SPI Time-out Error\n");
                return -ETIMEDOUT;
        }
        if (int_status & SPIFLG_DESYNC_MASK) {
                dev_err(sdev, "SPI Desynchronization Error\n");
                return -EIO;
        }
        if (int_status & SPIFLG_BITERR_MASK) {
                dev_err(sdev, "SPI Bit error\n");
                return -EIO;
        }

        if (dspi->version == SPI_VERSION_2) {
                if (int_status & SPIFLG_DLEN_ERR_MASK) {
                        dev_err(sdev, "SPI Data Length Error\n");
                        return -EIO;
                }
                if (int_status & SPIFLG_PARERR_MASK) {
                        dev_err(sdev, "SPI Parity Error\n");
                        return -EIO;
                }
                if (int_status & SPIFLG_OVRRUN_MASK) {
                        dev_err(sdev, "SPI Data Overrun error\n");
                        return -EIO;
                }
                if (int_status & SPIFLG_BUF_INIT_ACTIVE_MASK) {
                        dev_err(sdev, "SPI Buffer Init Active\n");
                        return -EBUSY;
                }
        }

        return 0;
}

/**
 * davinci_spi_process_events - check for and handle any SPI controller events
 * @dspi: the controller data
 *
 * This function will check the SPIFLG register and handle any events that are
 * detected there
 */
static int davinci_spi_process_events(struct davinci_spi *dspi)
{
        u32 buf, status, errors = 0, spidat1;

        buf = ioread32(dspi->base + SPIBUF);

        if (dspi->rcount > 0 && !(buf & SPIBUF_RXEMPTY_MASK)) {
                dspi->get_rx(buf & 0xFFFF, dspi);
                dspi->rcount--;
        }

        status = ioread32(dspi->base + SPIFLG);

        if (unlikely(status & SPIFLG_ERROR_MASK)) {
                errors = status & SPIFLG_ERROR_MASK;
                goto out;
        }

        if (dspi->wcount > 0 && !(buf & SPIBUF_TXFULL_MASK)) {
                spidat1 = ioread32(dspi->base + SPIDAT1);
                dspi->wcount--;
                spidat1 &= ~0xFFFF;
                spidat1 |= 0xFFFF & dspi->get_tx(dspi);
                iowrite32(spidat1, dspi->base + SPIDAT1);
        }

out:
        return errors;
}

static void davinci_spi_dma_rx_callback(void *data)
{
        struct davinci_spi *dspi = (struct davinci_spi *)data;

        dspi->rcount = 0;

        if (!dspi->wcount && !dspi->rcount)
                complete(&dspi->done);
}

static void davinci_spi_dma_tx_callback(void *data)
{
        struct davinci_spi *dspi = (struct davinci_spi *)data;

        dspi->wcount = 0;

        if (!dspi->wcount && !dspi->rcount)
                complete(&dspi->done);
}

/**
 * davinci_spi_bufs - functions which will handle transfer data
 * @spi: spi device on which data transfer to be done
 * @t: spi transfer in which transfer info is filled
 *
 * This function will put data to be transferred into data register
 * of SPI controller and then wait until the completion will be marked
 * by the IRQ Handler.
 */
static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
{
        struct davinci_spi *dspi;
        int data_type, ret = -ENOMEM;
        u32 tx_data, spidat1;
        u32 errors = 0;
        struct davinci_spi_config *spicfg;
        struct davinci_spi_platform_data *pdata;
        unsigned uninitialized_var(rx_buf_count);

        dspi = spi_master_get_devdata(spi->master);
        pdata = &dspi->pdata;
        spicfg = (struct davinci_spi_config *)spi->controller_data;
        if (!spicfg)
                spicfg = &davinci_spi_default_cfg;

        /* convert len to words based on bits_per_word */
        data_type = dspi->bytes_per_word[spi->chip_select];

        dspi->tx = t->tx_buf;
        dspi->rx = t->rx_buf;
        dspi->wcount = t->len / data_type;
        dspi->rcount = dspi->wcount;

        spidat1 = ioread32(dspi->base + SPIDAT1);

        clear_io_bits(dspi->base + SPIGCR1, SPIGCR1_POWERDOWN_MASK);
        set_io_bits(dspi->base + SPIGCR1, SPIGCR1_SPIENA_MASK);

        reinit_completion(&dspi->done);

        if (!davinci_spi_can_dma(spi->master, spi, t)) {
                if (spicfg->io_type != SPI_IO_TYPE_POLL)
                        set_io_bits(dspi->base + SPIINT, SPIINT_MASKINT);
                /* start the transfer */
                dspi->wcount--;
                tx_data = dspi->get_tx(dspi);
                spidat1 &= 0xFFFF0000;
                spidat1 |= tx_data & 0xFFFF;
                iowrite32(spidat1, dspi->base + SPIDAT1);
        } else {
                struct dma_slave_config dma_rx_conf = {
                        .direction = DMA_DEV_TO_MEM,
                        .src_addr = (unsigned long)dspi->pbase + SPIBUF,
                        .src_addr_width = data_type,
                        .src_maxburst = 1,
                };
                struct dma_slave_config dma_tx_conf = {
                        .direction = DMA_MEM_TO_DEV,
                        .dst_addr = (unsigned long)dspi->pbase + SPIDAT1,
                        .dst_addr_width = data_type,
                        .dst_maxburst = 1,
                };
                struct dma_async_tx_descriptor *rxdesc;
                struct dma_async_tx_descriptor *txdesc;

                dmaengine_slave_config(dspi->dma_rx, &dma_rx_conf);
                dmaengine_slave_config(dspi->dma_tx, &dma_tx_conf);

                rxdesc = dmaengine_prep_slave_sg(dspi->dma_rx,
                                t->rx_sg.sgl, t->rx_sg.nents, DMA_DEV_TO_MEM,
                                DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
                if (!rxdesc)
                        goto err_desc;

                if (!t->tx_buf) {
                        /* To avoid errors when doing rx-only transfers with
                         * many SG entries (> 20), use the rx buffer as the
                         * dummy tx buffer so that dma reloads are done at the
                         * same time for rx and tx.
                         */
                        t->tx_sg.sgl = t->rx_sg.sgl;
                        t->tx_sg.nents = t->rx_sg.nents;
                }

                txdesc = dmaengine_prep_slave_sg(dspi->dma_tx,
                                t->tx_sg.sgl, t->tx_sg.nents, DMA_MEM_TO_DEV,
                                DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
                if (!txdesc)
                        goto err_desc;

                rxdesc->callback = davinci_spi_dma_rx_callback;
                rxdesc->callback_param = (void *)dspi;
                txdesc->callback = davinci_spi_dma_tx_callback;
                txdesc->callback_param = (void *)dspi;

                if (pdata->cshold_bug)
                        iowrite16(spidat1 >> 16, dspi->base + SPIDAT1 + 2);

                dmaengine_submit(rxdesc);
                dmaengine_submit(txdesc);

                dma_async_issue_pending(dspi->dma_rx);
                dma_async_issue_pending(dspi->dma_tx);

                set_io_bits(dspi->base + SPIINT, SPIINT_DMA_REQ_EN);
        }

        /* Wait for the transfer to complete */
        if (spicfg->io_type != SPI_IO_TYPE_POLL) {
                if (wait_for_completion_timeout(&dspi->done, HZ) == 0)
                        errors = SPIFLG_TIMEOUT_MASK;
        } else {
                while (dspi->rcount > 0 || dspi->wcount > 0) {
                        errors = davinci_spi_process_events(dspi);
                        if (errors)
                                break;
                        cpu_relax();
                }
        }

        clear_io_bits(dspi->base + SPIINT, SPIINT_MASKALL);
        if (davinci_spi_can_dma(spi->master, spi, t))
                clear_io_bits(dspi->base + SPIINT, SPIINT_DMA_REQ_EN);

        clear_io_bits(dspi->base + SPIGCR1, SPIGCR1_SPIENA_MASK);
        set_io_bits(dspi->base + SPIGCR1, SPIGCR1_POWERDOWN_MASK);

        /*
         * Check for bit error, desync error,parity error,timeout error and
         * receive overflow errors
         */
        if (errors) {
                ret = davinci_spi_check_error(dspi, errors);
                WARN(!ret, "%s: error reported but no error found!\n",
                                                        dev_name(&spi->dev));
                return ret;
        }

        if (dspi->rcount != 0 || dspi->wcount != 0) {
                dev_err(&spi->dev, "SPI data transfer error\n");
                return -EIO;
        }

        return t->len;

err_desc:
        return ret;
}

/**
 * dummy_thread_fn - dummy thread function
 * @irq: IRQ number for this SPI Master
 * @context_data: structure for SPI Master controller davinci_spi
 *
 * This is to satisfy the request_threaded_irq() API so that the irq
 * handler is called in interrupt context.
 */
static irqreturn_t dummy_thread_fn(s32 irq, void *data)
{
        return IRQ_HANDLED;
}

/**
 * davinci_spi_irq - Interrupt handler for SPI Master Controller
 * @irq: IRQ number for this SPI Master
 * @context_data: structure for SPI Master controller davinci_spi
 *
 * ISR will determine that interrupt arrives either for READ or WRITE command.
 * According to command it will do the appropriate action. It will check
 * transfer length and if it is not zero then dispatch transfer command again.
 * If transfer length is zero then it will indicate the COMPLETION so that
 * davinci_spi_bufs function can go ahead.
 */
static irqreturn_t davinci_spi_irq(s32 irq, void *data)
{
        struct davinci_spi *dspi = data;
        int status;

        status = davinci_spi_process_events(dspi);
        if (unlikely(status != 0))
                clear_io_bits(dspi->base + SPIINT, SPIINT_MASKINT);

        if ((!dspi->rcount && !dspi->wcount) || status)
                complete(&dspi->done);

        return IRQ_HANDLED;
}

static int davinci_spi_request_dma(struct davinci_spi *dspi)
{
        struct device *sdev = dspi->bitbang.master->dev.parent;

        dspi->dma_rx = dma_request_chan(sdev, "rx");
        if (IS_ERR(dspi->dma_rx))
                return PTR_ERR(dspi->dma_rx);

        dspi->dma_tx = dma_request_chan(sdev, "tx");
        if (IS_ERR(dspi->dma_tx)) {
                dma_release_channel(dspi->dma_rx);
                return PTR_ERR(dspi->dma_tx);
        }

        return 0;
}

#if defined(CONFIG_OF)

/* OF SPI data structure */
struct davinci_spi_of_data {
        u8      version;
        u8      prescaler_limit;
};

static const struct davinci_spi_of_data dm6441_spi_data = {
        .version = SPI_VERSION_1,
        .prescaler_limit = 2,
};

static const struct davinci_spi_of_data da830_spi_data = {
        .version = SPI_VERSION_2,
        .prescaler_limit = 2,
};

static const struct davinci_spi_of_data keystone_spi_data = {
        .version = SPI_VERSION_1,
        .prescaler_limit = 0,
};

static const struct of_device_id davinci_spi_of_match[] = {
        {
                .compatible = "ti,dm6441-spi",
                .data = &dm6441_spi_data,
        },
        {
                .compatible = "ti,da830-spi",
                .data = &da830_spi_data,
        },
        {
                .compatible = "ti,keystone-spi",
                .data = &keystone_spi_data,
        },
        { },
};
MODULE_DEVICE_TABLE(of, davinci_spi_of_match);

/**
 * spi_davinci_get_pdata - Get platform data from DTS binding
 * @pdev: ptr to platform data
 * @dspi: ptr to driver data
 *
 * Parses and populates pdata in dspi from device tree bindings.
 *
 * NOTE: Not all platform data params are supported currently.
 */
static int spi_davinci_get_pdata(struct platform_device *pdev,
                        struct davinci_spi *dspi)
{
        struct device_node *node = pdev->dev.of_node;
        struct davinci_spi_of_data *spi_data;
        struct davinci_spi_platform_data *pdata;
        unsigned int num_cs, intr_line = 0;
        const struct of_device_id *match;

        pdata = &dspi->pdata;

        match = of_match_device(davinci_spi_of_match, &pdev->dev);
        if (!match)
                return -ENODEV;

        spi_data = (struct davinci_spi_of_data *)match->data;

        pdata->version = spi_data->version;
        pdata->prescaler_limit = spi_data->prescaler_limit;
        /*
         * default num_cs is 1 and all chipsel are internal to the chip
         * indicated by chip_sel being NULL or cs_gpios being NULL or
         * set to -ENOENT. num-cs includes internal as well as gpios.
         * indicated by chip_sel being NULL. GPIO based CS is not
         * supported yet in DT bindings.
         */
        num_cs = 1;
        of_property_read_u32(node, "num-cs", &num_cs);
        pdata->num_chipselect = num_cs;
        of_property_read_u32(node, "ti,davinci-spi-intr-line", &intr_line);
        pdata->intr_line = intr_line;
        return 0;
}
#else
static int spi_davinci_get_pdata(struct platform_device *pdev,
                        struct davinci_spi *dspi)
{
        return -ENODEV;
}
#endif

/**
 * davinci_spi_probe - probe function for SPI Master Controller
 * @pdev: platform_device structure which contains plateform specific data
 *
 * According to Linux Device Model this function will be invoked by Linux
 * with platform_device struct which contains the device specific info.
 * This function will map the SPI controller's memory, register IRQ,
 * Reset SPI controller and setting its registers to default value.
 * It will invoke spi_bitbang_start to create work queue so that client driver
 * can register transfer method to work queue.
 */
static int davinci_spi_probe(struct platform_device *pdev)
{
        struct spi_master *master;
        struct davinci_spi *dspi;
        struct davinci_spi_platform_data *pdata;
        struct resource *r;
        int ret = 0;
        u32 spipc0;

        master = spi_alloc_master(&pdev->dev, sizeof(struct davinci_spi));
        if (master == NULL) {
                ret = -ENOMEM;
                goto err;
        }

        platform_set_drvdata(pdev, master);

        dspi = spi_master_get_devdata(master);

        if (dev_get_platdata(&pdev->dev)) {
                pdata = dev_get_platdata(&pdev->dev);
                dspi->pdata = *pdata;
        } else {
                /* update dspi pdata with that from the DT */
                ret = spi_davinci_get_pdata(pdev, dspi);
                if (ret < 0)
                        goto free_master;
        }

        /* pdata in dspi is now updated and point pdata to that */
        pdata = &dspi->pdata;

        dspi->bytes_per_word = devm_kcalloc(&pdev->dev,
                                            pdata->num_chipselect,
                                            sizeof(*dspi->bytes_per_word),
                                            GFP_KERNEL);
        if (dspi->bytes_per_word == NULL) {
                ret = -ENOMEM;
                goto free_master;
        }

        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (r == NULL) {
                ret = -ENOENT;
                goto free_master;
        }

        dspi->pbase = r->start;

        dspi->base = devm_ioremap_resource(&pdev->dev, r);
        if (IS_ERR(dspi->base)) {
                ret = PTR_ERR(dspi->base);
                goto free_master;
        }

        init_completion(&dspi->done);

        ret = platform_get_irq(pdev, 0);
        if (ret == 0)
                ret = -EINVAL;
        if (ret < 0)
                goto free_master;
        dspi->irq = ret;

        ret = devm_request_threaded_irq(&pdev->dev, dspi->irq, davinci_spi_irq,
                                dummy_thread_fn, 0, dev_name(&pdev->dev), dspi);
        if (ret)
                goto free_master;

        dspi->bitbang.master = master;

        dspi->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(dspi->clk)) {
                ret = -ENODEV;
                goto free_master;
        }
        ret = clk_prepare_enable(dspi->clk);
        if (ret)
                goto free_master;

        master->use_gpio_descriptors = true;
        master->dev.of_node = pdev->dev.of_node;
        master->bus_num = pdev->id;
        master->num_chipselect = pdata->num_chipselect;
        master->bits_per_word_mask = SPI_BPW_RANGE_MASK(2, 16);
        master->flags = SPI_MASTER_MUST_RX;
        master->setup = davinci_spi_setup;
        master->cleanup = davinci_spi_cleanup;
        master->can_dma = davinci_spi_can_dma;

        dspi->bitbang.chipselect = davinci_spi_chipselect;
        dspi->bitbang.setup_transfer = davinci_spi_setup_transfer;
        dspi->prescaler_limit = pdata->prescaler_limit;
        dspi->version = pdata->version;

        dspi->bitbang.flags = SPI_NO_CS | SPI_LSB_FIRST | SPI_LOOP | SPI_CS_WORD;
        if (dspi->version == SPI_VERSION_2)
                dspi->bitbang.flags |= SPI_READY;

        dspi->bitbang.txrx_bufs = davinci_spi_bufs;

        ret = davinci_spi_request_dma(dspi);
        if (ret == -EPROBE_DEFER) {
                goto free_clk;
        } else if (ret) {
                dev_info(&pdev->dev, "DMA is not supported (%d)\n", ret);
                dspi->dma_rx = NULL;
                dspi->dma_tx = NULL;
        }

        dspi->get_rx = davinci_spi_rx_buf_u8;
        dspi->get_tx = davinci_spi_tx_buf_u8;

        /* Reset In/OUT SPI module */
        iowrite32(0, dspi->base + SPIGCR0);
        udelay(100);
        iowrite32(1, dspi->base + SPIGCR0);

        /* Set up SPIPC0.  CS and ENA init is done in davinci_spi_setup */
        spipc0 = SPIPC0_DIFUN_MASK | SPIPC0_DOFUN_MASK | SPIPC0_CLKFUN_MASK;
        iowrite32(spipc0, dspi->base + SPIPC0);

        if (pdata->intr_line)
                iowrite32(SPI_INTLVL_1, dspi->base + SPILVL);
        else
                iowrite32(SPI_INTLVL_0, dspi->base + SPILVL);

        iowrite32(CS_DEFAULT, dspi->base + SPIDEF);

        /* master mode default */
        set_io_bits(dspi->base + SPIGCR1, SPIGCR1_CLKMOD_MASK);
        set_io_bits(dspi->base + SPIGCR1, SPIGCR1_MASTER_MASK);
        set_io_bits(dspi->base + SPIGCR1, SPIGCR1_POWERDOWN_MASK);

        ret = spi_bitbang_start(&dspi->bitbang);
        if (ret)
                goto free_dma;

        dev_info(&pdev->dev, "Controller at 0x%p\n", dspi->base);

        return ret;

free_dma:
        if (dspi->dma_rx) {
                dma_release_channel(dspi->dma_rx);
                dma_release_channel(dspi->dma_tx);
        }
free_clk:
        clk_disable_unprepare(dspi->clk);
free_master:
        spi_master_put(master);
err:
        return ret;
}

/**
 * davinci_spi_remove - remove function for SPI Master Controller
 * @pdev: platform_device structure which contains plateform specific data
 *
 * This function will do the reverse action of davinci_spi_probe function
 * It will free the IRQ and SPI controller's memory region.
 * It will also call spi_bitbang_stop to destroy the work queue which was
 * created by spi_bitbang_start.
 */
static int davinci_spi_remove(struct platform_device *pdev)
{
        struct davinci_spi *dspi;
        struct spi_master *master;

        master = platform_get_drvdata(pdev);
        dspi = spi_master_get_devdata(master);

        spi_bitbang_stop(&dspi->bitbang);

        clk_disable_unprepare(dspi->clk);
        spi_master_put(master);

        if (dspi->dma_rx) {
                dma_release_channel(dspi->dma_rx);
                dma_release_channel(dspi->dma_tx);
        }

        return 0;
}

static struct platform_driver davinci_spi_driver = {
        .driver = {
                .name = "spi_davinci",
                .of_match_table = of_match_ptr(davinci_spi_of_match),
        },
        .probe = davinci_spi_probe,
        .remove = davinci_spi_remove,
};
module_platform_driver(davinci_spi_driver);

MODULE_DESCRIPTION("TI DaVinci SPI Master Controller Driver");
MODULE_LICENSE("GPL");