LiteX: driver for MMCM

[linux/fpc-iii.git] / drivers / spi / spi-dw-core.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Designware SPI core controller driver (refer pxa2xx_spi.c)
 *
 * Copyright (c) 2009, Intel Corporation.
 */

#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/preempt.h>
#include <linux/highmem.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi-mem.h>
#include <linux/string.h>
#include <linux/of.h>

#include "spi-dw.h"

#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
#endif

/* Slave spi_device related */
struct chip_data {
        u32 cr0;
        u32 rx_sample_dly;      /* RX sample delay */
};

#ifdef CONFIG_DEBUG_FS

#define DW_SPI_DBGFS_REG(_name, _off)   \
{                                       \
        .name = _name,                  \
        .offset = _off,                 \
}

static const struct debugfs_reg32 dw_spi_dbgfs_regs[] = {
        DW_SPI_DBGFS_REG("CTRLR0", DW_SPI_CTRLR0),
        DW_SPI_DBGFS_REG("CTRLR1", DW_SPI_CTRLR1),
        DW_SPI_DBGFS_REG("SSIENR", DW_SPI_SSIENR),
        DW_SPI_DBGFS_REG("SER", DW_SPI_SER),
        DW_SPI_DBGFS_REG("BAUDR", DW_SPI_BAUDR),
        DW_SPI_DBGFS_REG("TXFTLR", DW_SPI_TXFTLR),
        DW_SPI_DBGFS_REG("RXFTLR", DW_SPI_RXFTLR),
        DW_SPI_DBGFS_REG("TXFLR", DW_SPI_TXFLR),
        DW_SPI_DBGFS_REG("RXFLR", DW_SPI_RXFLR),
        DW_SPI_DBGFS_REG("SR", DW_SPI_SR),
        DW_SPI_DBGFS_REG("IMR", DW_SPI_IMR),
        DW_SPI_DBGFS_REG("ISR", DW_SPI_ISR),
        DW_SPI_DBGFS_REG("DMACR", DW_SPI_DMACR),
        DW_SPI_DBGFS_REG("DMATDLR", DW_SPI_DMATDLR),
        DW_SPI_DBGFS_REG("DMARDLR", DW_SPI_DMARDLR),
        DW_SPI_DBGFS_REG("RX_SAMPLE_DLY", DW_SPI_RX_SAMPLE_DLY),
};

static int dw_spi_debugfs_init(struct dw_spi *dws)
{
        char name[32];

        snprintf(name, 32, "dw_spi%d", dws->master->bus_num);
        dws->debugfs = debugfs_create_dir(name, NULL);
        if (!dws->debugfs)
                return -ENOMEM;

        dws->regset.regs = dw_spi_dbgfs_regs;
        dws->regset.nregs = ARRAY_SIZE(dw_spi_dbgfs_regs);
        dws->regset.base = dws->regs;
        debugfs_create_regset32("registers", 0400, dws->debugfs, &dws->regset);

        return 0;
}

static void dw_spi_debugfs_remove(struct dw_spi *dws)
{
        debugfs_remove_recursive(dws->debugfs);
}

#else
static inline int dw_spi_debugfs_init(struct dw_spi *dws)
{
        return 0;
}

static inline void dw_spi_debugfs_remove(struct dw_spi *dws)
{
}
#endif /* CONFIG_DEBUG_FS */

void dw_spi_set_cs(struct spi_device *spi, bool enable)
{
        struct dw_spi *dws = spi_controller_get_devdata(spi->controller);
        bool cs_high = !!(spi->mode & SPI_CS_HIGH);

        /*
         * DW SPI controller demands any native CS being set in order to
         * proceed with data transfer. So in order to activate the SPI
         * communications we must set a corresponding bit in the Slave
         * Enable register no matter whether the SPI core is configured to
         * support active-high or active-low CS level.
         */
        if (cs_high == enable)
                dw_writel(dws, DW_SPI_SER, BIT(spi->chip_select));
        else
                dw_writel(dws, DW_SPI_SER, 0);
}
EXPORT_SYMBOL_GPL(dw_spi_set_cs);

/* Return the max entries we can fill into tx fifo */
static inline u32 tx_max(struct dw_spi *dws)
{
        u32 tx_room, rxtx_gap;

        tx_room = dws->fifo_len - dw_readl(dws, DW_SPI_TXFLR);

        /*
         * Another concern is about the tx/rx mismatch, we
         * though to use (dws->fifo_len - rxflr - txflr) as
         * one maximum value for tx, but it doesn't cover the
         * data which is out of tx/rx fifo and inside the
         * shift registers. So a control from sw point of
         * view is taken.
         */
        rxtx_gap = dws->fifo_len - (dws->rx_len - dws->tx_len);

        return min3((u32)dws->tx_len, tx_room, rxtx_gap);
}

/* Return the max entries we should read out of rx fifo */
static inline u32 rx_max(struct dw_spi *dws)
{
        return min_t(u32, dws->rx_len, dw_readl(dws, DW_SPI_RXFLR));
}

static void dw_writer(struct dw_spi *dws)
{
        u32 max = tx_max(dws);
        u32 txw = 0;

        while (max--) {
                if (dws->tx) {
                        if (dws->n_bytes == 1)
                                txw = *(u8 *)(dws->tx);
                        else if (dws->n_bytes == 2)
                                txw = *(u16 *)(dws->tx);
                        else
                                txw = *(u32 *)(dws->tx);

                        dws->tx += dws->n_bytes;
                }
                dw_write_io_reg(dws, DW_SPI_DR, txw);
                --dws->tx_len;
        }
}

static void dw_reader(struct dw_spi *dws)
{
        u32 max = rx_max(dws);
        u32 rxw;

        while (max--) {
                rxw = dw_read_io_reg(dws, DW_SPI_DR);
                if (dws->rx) {
                        if (dws->n_bytes == 1)
                                *(u8 *)(dws->rx) = rxw;
                        else if (dws->n_bytes == 2)
                                *(u16 *)(dws->rx) = rxw;
                        else
                                *(u32 *)(dws->rx) = rxw;

                        dws->rx += dws->n_bytes;
                }
                --dws->rx_len;
        }
}

int dw_spi_check_status(struct dw_spi *dws, bool raw)
{
        u32 irq_status;
        int ret = 0;

        if (raw)
                irq_status = dw_readl(dws, DW_SPI_RISR);
        else
                irq_status = dw_readl(dws, DW_SPI_ISR);

        if (irq_status & SPI_INT_RXOI) {
                dev_err(&dws->master->dev, "RX FIFO overflow detected\n");
                ret = -EIO;
        }

        if (irq_status & SPI_INT_RXUI) {
                dev_err(&dws->master->dev, "RX FIFO underflow detected\n");
                ret = -EIO;
        }

        if (irq_status & SPI_INT_TXOI) {
                dev_err(&dws->master->dev, "TX FIFO overflow detected\n");
                ret = -EIO;
        }

        /* Generically handle the erroneous situation */
        if (ret) {
                spi_reset_chip(dws);
                if (dws->master->cur_msg)
                        dws->master->cur_msg->status = ret;
        }

        return ret;
}
EXPORT_SYMBOL_GPL(dw_spi_check_status);

static irqreturn_t dw_spi_transfer_handler(struct dw_spi *dws)
{
        u16 irq_status = dw_readl(dws, DW_SPI_ISR);

        if (dw_spi_check_status(dws, false)) {
                spi_finalize_current_transfer(dws->master);
                return IRQ_HANDLED;
        }

        /*
         * Read data from the Rx FIFO every time we've got a chance executing
         * this method. If there is nothing left to receive, terminate the
         * procedure. Otherwise adjust the Rx FIFO Threshold level if it's a
         * final stage of the transfer. By doing so we'll get the next IRQ
         * right when the leftover incoming data is received.
         */
        dw_reader(dws);
        if (!dws->rx_len) {
                spi_mask_intr(dws, 0xff);
                spi_finalize_current_transfer(dws->master);
        } else if (dws->rx_len <= dw_readl(dws, DW_SPI_RXFTLR)) {
                dw_writel(dws, DW_SPI_RXFTLR, dws->rx_len - 1);
        }

        /*
         * Send data out if Tx FIFO Empty IRQ is received. The IRQ will be
         * disabled after the data transmission is finished so not to
         * have the TXE IRQ flood at the final stage of the transfer.
         */
        if (irq_status & SPI_INT_TXEI) {
                dw_writer(dws);
                if (!dws->tx_len)
                        spi_mask_intr(dws, SPI_INT_TXEI);
        }

        return IRQ_HANDLED;
}

static irqreturn_t dw_spi_irq(int irq, void *dev_id)
{
        struct spi_controller *master = dev_id;
        struct dw_spi *dws = spi_controller_get_devdata(master);
        u16 irq_status = dw_readl(dws, DW_SPI_ISR) & 0x3f;

        if (!irq_status)
                return IRQ_NONE;

        if (!master->cur_msg) {
                spi_mask_intr(dws, 0xff);
                return IRQ_HANDLED;
        }

        return dws->transfer_handler(dws);
}

static u32 dw_spi_prepare_cr0(struct dw_spi *dws, struct spi_device *spi)
{
        u32 cr0 = 0;

        if (!(dws->caps & DW_SPI_CAP_DWC_SSI)) {
                /* CTRLR0[ 5: 4] Frame Format */
                cr0 |= SSI_MOTO_SPI << SPI_FRF_OFFSET;

                /*
                 * SPI mode (SCPOL|SCPH)
                 * CTRLR0[ 6] Serial Clock Phase
                 * CTRLR0[ 7] Serial Clock Polarity
                 */
                cr0 |= ((spi->mode & SPI_CPOL) ? 1 : 0) << SPI_SCOL_OFFSET;
                cr0 |= ((spi->mode & SPI_CPHA) ? 1 : 0) << SPI_SCPH_OFFSET;

                /* CTRLR0[11] Shift Register Loop */
                cr0 |= ((spi->mode & SPI_LOOP) ? 1 : 0) << SPI_SRL_OFFSET;
        } else {
                /* CTRLR0[ 7: 6] Frame Format */
                cr0 |= SSI_MOTO_SPI << DWC_SSI_CTRLR0_FRF_OFFSET;

                /*
                 * SPI mode (SCPOL|SCPH)
                 * CTRLR0[ 8] Serial Clock Phase
                 * CTRLR0[ 9] Serial Clock Polarity
                 */
                cr0 |= ((spi->mode & SPI_CPOL) ? 1 : 0) << DWC_SSI_CTRLR0_SCPOL_OFFSET;
                cr0 |= ((spi->mode & SPI_CPHA) ? 1 : 0) << DWC_SSI_CTRLR0_SCPH_OFFSET;

                /* CTRLR0[13] Shift Register Loop */
                cr0 |= ((spi->mode & SPI_LOOP) ? 1 : 0) << DWC_SSI_CTRLR0_SRL_OFFSET;

                if (dws->caps & DW_SPI_CAP_KEEMBAY_MST)
                        cr0 |= DWC_SSI_CTRLR0_KEEMBAY_MST;
        }

        return cr0;
}

void dw_spi_update_config(struct dw_spi *dws, struct spi_device *spi,
                          struct dw_spi_cfg *cfg)
{
        struct chip_data *chip = spi_get_ctldata(spi);
        u32 cr0 = chip->cr0;
        u32 speed_hz;
        u16 clk_div;

        /* CTRLR0[ 4/3: 0] or CTRLR0[ 20: 16] Data Frame Size */
        cr0 |= (cfg->dfs - 1) << dws->dfs_offset;

        if (!(dws->caps & DW_SPI_CAP_DWC_SSI))
                /* CTRLR0[ 9:8] Transfer Mode */
                cr0 |= cfg->tmode << SPI_TMOD_OFFSET;
        else
                /* CTRLR0[11:10] Transfer Mode */
                cr0 |= cfg->tmode << DWC_SSI_CTRLR0_TMOD_OFFSET;

        dw_writel(dws, DW_SPI_CTRLR0, cr0);

        if (cfg->tmode == SPI_TMOD_EPROMREAD || cfg->tmode == SPI_TMOD_RO)
                dw_writel(dws, DW_SPI_CTRLR1, cfg->ndf ? cfg->ndf - 1 : 0);

        /* Note DW APB SSI clock divider doesn't support odd numbers */
        clk_div = (DIV_ROUND_UP(dws->max_freq, cfg->freq) + 1) & 0xfffe;
        speed_hz = dws->max_freq / clk_div;

        if (dws->current_freq != speed_hz) {
                spi_set_clk(dws, clk_div);
                dws->current_freq = speed_hz;
        }

        /* Update RX sample delay if required */
        if (dws->cur_rx_sample_dly != chip->rx_sample_dly) {
                dw_writel(dws, DW_SPI_RX_SAMPLE_DLY, chip->rx_sample_dly);
                dws->cur_rx_sample_dly = chip->rx_sample_dly;
        }
}
EXPORT_SYMBOL_GPL(dw_spi_update_config);

static void dw_spi_irq_setup(struct dw_spi *dws)
{
        u16 level;
        u8 imask;

        /*
         * Originally Tx and Rx data lengths match. Rx FIFO Threshold level
         * will be adjusted at the final stage of the IRQ-based SPI transfer
         * execution so not to lose the leftover of the incoming data.
         */
        level = min_t(u16, dws->fifo_len / 2, dws->tx_len);
        dw_writel(dws, DW_SPI_TXFTLR, level);
        dw_writel(dws, DW_SPI_RXFTLR, level - 1);

        dws->transfer_handler = dw_spi_transfer_handler;

        imask = SPI_INT_TXEI | SPI_INT_TXOI | SPI_INT_RXUI | SPI_INT_RXOI |
                SPI_INT_RXFI;
        spi_umask_intr(dws, imask);
}

/*
 * The iterative procedure of the poll-based transfer is simple: write as much
 * as possible to the Tx FIFO, wait until the pending to receive data is ready
 * to be read, read it from the Rx FIFO and check whether the performed
 * procedure has been successful.
 *
 * Note this method the same way as the IRQ-based transfer won't work well for
 * the SPI devices connected to the controller with native CS due to the
 * automatic CS assertion/de-assertion.
 */
static int dw_spi_poll_transfer(struct dw_spi *dws,
                                struct spi_transfer *transfer)
{
        struct spi_delay delay;
        u16 nbits;
        int ret;

        delay.unit = SPI_DELAY_UNIT_SCK;
        nbits = dws->n_bytes * BITS_PER_BYTE;

        do {
                dw_writer(dws);

                delay.value = nbits * (dws->rx_len - dws->tx_len);
                spi_delay_exec(&delay, transfer);

                dw_reader(dws);

                ret = dw_spi_check_status(dws, true);
                if (ret)
                        return ret;
        } while (dws->rx_len);

        return 0;
}

static int dw_spi_transfer_one(struct spi_controller *master,
                struct spi_device *spi, struct spi_transfer *transfer)
{
        struct dw_spi *dws = spi_controller_get_devdata(master);
        struct dw_spi_cfg cfg = {
                .tmode = SPI_TMOD_TR,
                .dfs = transfer->bits_per_word,
                .freq = transfer->speed_hz,
        };
        int ret;

        dws->dma_mapped = 0;
        dws->n_bytes = DIV_ROUND_UP(transfer->bits_per_word, BITS_PER_BYTE);
        dws->tx = (void *)transfer->tx_buf;
        dws->tx_len = transfer->len / dws->n_bytes;
        dws->rx = transfer->rx_buf;
        dws->rx_len = dws->tx_len;

        /* Ensure the data above is visible for all CPUs */
        smp_mb();

        spi_enable_chip(dws, 0);

        dw_spi_update_config(dws, spi, &cfg);

        transfer->effective_speed_hz = dws->current_freq;

        /* Check if current transfer is a DMA transaction */
        if (master->can_dma && master->can_dma(master, spi, transfer))
                dws->dma_mapped = master->cur_msg_mapped;

        /* For poll mode just disable all interrupts */
        spi_mask_intr(dws, 0xff);

        if (dws->dma_mapped) {
                ret = dws->dma_ops->dma_setup(dws, transfer);
                if (ret)
                        return ret;
        }

        spi_enable_chip(dws, 1);

        if (dws->dma_mapped)
                return dws->dma_ops->dma_transfer(dws, transfer);
        else if (dws->irq == IRQ_NOTCONNECTED)
                return dw_spi_poll_transfer(dws, transfer);

        dw_spi_irq_setup(dws);

        return 1;
}

static void dw_spi_handle_err(struct spi_controller *master,
                struct spi_message *msg)
{
        struct dw_spi *dws = spi_controller_get_devdata(master);

        if (dws->dma_mapped)
                dws->dma_ops->dma_stop(dws);

        spi_reset_chip(dws);
}

static int dw_spi_adjust_mem_op_size(struct spi_mem *mem, struct spi_mem_op *op)
{
        if (op->data.dir == SPI_MEM_DATA_IN)
                op->data.nbytes = clamp_val(op->data.nbytes, 0, SPI_NDF_MASK + 1);

        return 0;
}

static bool dw_spi_supports_mem_op(struct spi_mem *mem,
                                   const struct spi_mem_op *op)
{
        if (op->data.buswidth > 1 || op->addr.buswidth > 1 ||
            op->dummy.buswidth > 1 || op->cmd.buswidth > 1)
                return false;

        return spi_mem_default_supports_op(mem, op);
}

static int dw_spi_init_mem_buf(struct dw_spi *dws, const struct spi_mem_op *op)
{
        unsigned int i, j, len;
        u8 *out;

        /*
         * Calculate the total length of the EEPROM command transfer and
         * either use the pre-allocated buffer or create a temporary one.
         */
        len = op->cmd.nbytes + op->addr.nbytes + op->dummy.nbytes;
        if (op->data.dir == SPI_MEM_DATA_OUT)
                len += op->data.nbytes;

        if (len <= SPI_BUF_SIZE) {
                out = dws->buf;
        } else {
                out = kzalloc(len, GFP_KERNEL);
                if (!out)
                        return -ENOMEM;
        }

        /*
         * Collect the operation code, address and dummy bytes into the single
         * buffer. If it's a transfer with data to be sent, also copy it into the
         * single buffer in order to speed the data transmission up.
         */
        for (i = 0; i < op->cmd.nbytes; ++i)
                out[i] = SPI_GET_BYTE(op->cmd.opcode, op->cmd.nbytes - i - 1);
        for (j = 0; j < op->addr.nbytes; ++i, ++j)
                out[i] = SPI_GET_BYTE(op->addr.val, op->addr.nbytes - j - 1);
        for (j = 0; j < op->dummy.nbytes; ++i, ++j)
                out[i] = 0x0;

        if (op->data.dir == SPI_MEM_DATA_OUT)
                memcpy(&out[i], op->data.buf.out, op->data.nbytes);

        dws->n_bytes = 1;
        dws->tx = out;
        dws->tx_len = len;
        if (op->data.dir == SPI_MEM_DATA_IN) {
                dws->rx = op->data.buf.in;
                dws->rx_len = op->data.nbytes;
        } else {
                dws->rx = NULL;
                dws->rx_len = 0;
        }

        return 0;
}

static void dw_spi_free_mem_buf(struct dw_spi *dws)
{
        if (dws->tx != dws->buf)
                kfree(dws->tx);
}

static int dw_spi_write_then_read(struct dw_spi *dws, struct spi_device *spi)
{
        u32 room, entries, sts;
        unsigned int len;
        u8 *buf;

        /*
         * At initial stage we just pre-fill the Tx FIFO in with no rush,
         * since native CS hasn't been enabled yet and the automatic data
         * transmission won't start til we do that.
         */
        len = min(dws->fifo_len, dws->tx_len);
        buf = dws->tx;
        while (len--)
                dw_write_io_reg(dws, DW_SPI_DR, *buf++);

        /*
         * After setting any bit in the SER register the transmission will
         * start automatically. We have to keep up with that procedure
         * otherwise the CS de-assertion will happen whereupon the memory
         * operation will be pre-terminated.
         */
        len = dws->tx_len - ((void *)buf - dws->tx);
        dw_spi_set_cs(spi, false);
        while (len) {
                entries = readl_relaxed(dws->regs + DW_SPI_TXFLR);
                if (!entries) {
                        dev_err(&dws->master->dev, "CS de-assertion on Tx\n");
                        return -EIO;
                }
                room = min(dws->fifo_len - entries, len);
                for (; room; --room, --len)
                        dw_write_io_reg(dws, DW_SPI_DR, *buf++);
        }

        /*
         * Data fetching will start automatically if the EEPROM-read mode is
         * activated. We have to keep up with the incoming data pace to
         * prevent the Rx FIFO overflow causing the inbound data loss.
         */
        len = dws->rx_len;
        buf = dws->rx;
        while (len) {
                entries = readl_relaxed(dws->regs + DW_SPI_RXFLR);
                if (!entries) {
                        sts = readl_relaxed(dws->regs + DW_SPI_RISR);
                        if (sts & SPI_INT_RXOI) {
                                dev_err(&dws->master->dev, "FIFO overflow on Rx\n");
                                return -EIO;
                        }
                        continue;
                }
                entries = min(entries, len);
                for (; entries; --entries, --len)
                        *buf++ = dw_read_io_reg(dws, DW_SPI_DR);
        }

        return 0;
}

static inline bool dw_spi_ctlr_busy(struct dw_spi *dws)
{
        return dw_readl(dws, DW_SPI_SR) & SR_BUSY;
}

static int dw_spi_wait_mem_op_done(struct dw_spi *dws)
{
        int retry = SPI_WAIT_RETRIES;
        struct spi_delay delay;
        unsigned long ns, us;
        u32 nents;

        nents = dw_readl(dws, DW_SPI_TXFLR);
        ns = NSEC_PER_SEC / dws->current_freq * nents;
        ns *= dws->n_bytes * BITS_PER_BYTE;
        if (ns <= NSEC_PER_USEC) {
                delay.unit = SPI_DELAY_UNIT_NSECS;
                delay.value = ns;
        } else {
                us = DIV_ROUND_UP(ns, NSEC_PER_USEC);
                delay.unit = SPI_DELAY_UNIT_USECS;
                delay.value = clamp_val(us, 0, USHRT_MAX);
        }

        while (dw_spi_ctlr_busy(dws) && retry--)
                spi_delay_exec(&delay, NULL);

        if (retry < 0) {
                dev_err(&dws->master->dev, "Mem op hanged up\n");
                return -EIO;
        }

        return 0;
}

static void dw_spi_stop_mem_op(struct dw_spi *dws, struct spi_device *spi)
{
        spi_enable_chip(dws, 0);
        dw_spi_set_cs(spi, true);
        spi_enable_chip(dws, 1);
}

/*
 * The SPI memory operation implementation below is the best choice for the
 * devices, which are selected by the native chip-select lane. It's
 * specifically developed to workaround the problem with automatic chip-select
 * lane toggle when there is no data in the Tx FIFO buffer. Luckily the current
 * SPI-mem core calls exec_op() callback only if the GPIO-based CS is
 * unavailable.
 */
static int dw_spi_exec_mem_op(struct spi_mem *mem, const struct spi_mem_op *op)
{
        struct dw_spi *dws = spi_controller_get_devdata(mem->spi->controller);
        struct dw_spi_cfg cfg;
        unsigned long flags;
        int ret;

        /*
         * Collect the outbound data into a single buffer to speed the
         * transmission up at least on the initial stage.
         */
        ret = dw_spi_init_mem_buf(dws, op);
        if (ret)
                return ret;

        /*
         * DW SPI EEPROM-read mode is required only for the SPI memory Data-IN
         * operation. Transmit-only mode is suitable for the rest of them.
         */
        cfg.dfs = 8;
        cfg.freq = clamp(mem->spi->max_speed_hz, 0U, dws->max_mem_freq);
        if (op->data.dir == SPI_MEM_DATA_IN) {
                cfg.tmode = SPI_TMOD_EPROMREAD;
                cfg.ndf = op->data.nbytes;
        } else {
                cfg.tmode = SPI_TMOD_TO;
        }

        spi_enable_chip(dws, 0);

        dw_spi_update_config(dws, mem->spi, &cfg);

        spi_mask_intr(dws, 0xff);

        spi_enable_chip(dws, 1);

        /*
         * DW APB SSI controller has very nasty peculiarities. First originally
         * (without any vendor-specific modifications) it doesn't provide a
         * direct way to set and clear the native chip-select signal. Instead
         * the controller asserts the CS lane if Tx FIFO isn't empty and a
         * transmission is going on, and automatically de-asserts it back to
         * the high level if the Tx FIFO doesn't have anything to be pushed
         * out. Due to that a multi-tasking or heavy IRQs activity might be
         * fatal, since the transfer procedure preemption may cause the Tx FIFO
         * getting empty and sudden CS de-assertion, which in the middle of the
         * transfer will most likely cause the data loss. Secondly the
         * EEPROM-read or Read-only DW SPI transfer modes imply the incoming
         * data being automatically pulled in into the Rx FIFO. So if the
         * driver software is late in fetching the data from the FIFO before
         * it's overflown, new incoming data will be lost. In order to make
         * sure the executed memory operations are CS-atomic and to prevent the
         * Rx FIFO overflow we have to disable the local interrupts so to block
         * any preemption during the subsequent IO operations.
         *
         * Note. At some circumstances disabling IRQs may not help to prevent
         * the problems described above. The CS de-assertion and Rx FIFO
         * overflow may still happen due to the relatively slow system bus or
         * CPU not working fast enough, so the write-then-read algo implemented
         * here just won't keep up with the SPI bus data transfer. Such
         * situation is highly platform specific and is supposed to be fixed by
         * manually restricting the SPI bus frequency using the
         * dws->max_mem_freq parameter.
         */
        local_irq_save(flags);
        preempt_disable();

        ret = dw_spi_write_then_read(dws, mem->spi);

        local_irq_restore(flags);
        preempt_enable();

        /*
         * Wait for the operation being finished and check the controller
         * status only if there hasn't been any run-time error detected. In the
         * former case it's just pointless. In the later one to prevent an
         * additional error message printing since any hw error flag being set
         * would be due to an error detected on the data transfer.
         */
        if (!ret) {
                ret = dw_spi_wait_mem_op_done(dws);
                if (!ret)
                        ret = dw_spi_check_status(dws, true);
        }

        dw_spi_stop_mem_op(dws, mem->spi);

        dw_spi_free_mem_buf(dws);

        return ret;
}

/*
 * Initialize the default memory operations if a glue layer hasn't specified
 * custom ones. Direct mapping operations will be preserved anyway since DW SPI
 * controller doesn't have an embedded dirmap interface. Note the memory
 * operations implemented in this driver is the best choice only for the DW APB
 * SSI controller with standard native CS functionality. If a hardware vendor
 * has fixed the automatic CS assertion/de-assertion peculiarity, then it will
 * be safer to use the normal SPI-messages-based transfers implementation.
 */
static void dw_spi_init_mem_ops(struct dw_spi *dws)
{
        if (!dws->mem_ops.exec_op && !(dws->caps & DW_SPI_CAP_CS_OVERRIDE) &&
            !dws->set_cs) {
                dws->mem_ops.adjust_op_size = dw_spi_adjust_mem_op_size;
                dws->mem_ops.supports_op = dw_spi_supports_mem_op;
                dws->mem_ops.exec_op = dw_spi_exec_mem_op;
                if (!dws->max_mem_freq)
                        dws->max_mem_freq = dws->max_freq;
        }
}

/* This may be called twice for each spi dev */
static int dw_spi_setup(struct spi_device *spi)
{
        struct dw_spi *dws = spi_controller_get_devdata(spi->controller);
        struct chip_data *chip;

        /* Only alloc on first setup */
        chip = spi_get_ctldata(spi);
        if (!chip) {
                struct dw_spi *dws = spi_controller_get_devdata(spi->controller);
                u32 rx_sample_dly_ns;

                chip = kzalloc(sizeof(struct chip_data), GFP_KERNEL);
                if (!chip)
                        return -ENOMEM;
                spi_set_ctldata(spi, chip);
                /* Get specific / default rx-sample-delay */
                if (device_property_read_u32(&spi->dev,
                                             "rx-sample-delay-ns",
                                             &rx_sample_dly_ns) != 0)
                        /* Use default controller value */
                        rx_sample_dly_ns = dws->def_rx_sample_dly_ns;
                chip->rx_sample_dly = DIV_ROUND_CLOSEST(rx_sample_dly_ns,
                                                        NSEC_PER_SEC /
                                                        dws->max_freq);
        }

        /*
         * Update CR0 data each time the setup callback is invoked since
         * the device parameters could have been changed, for instance, by
         * the MMC SPI driver or something else.
         */
        chip->cr0 = dw_spi_prepare_cr0(dws, spi);

        return 0;
}

static void dw_spi_cleanup(struct spi_device *spi)
{
        struct chip_data *chip = spi_get_ctldata(spi);

        kfree(chip);
        spi_set_ctldata(spi, NULL);
}

/* Restart the controller, disable all interrupts, clean rx fifo */
static void spi_hw_init(struct device *dev, struct dw_spi *dws)
{
        spi_reset_chip(dws);

        /*
         * Try to detect the FIFO depth if not set by interface driver,
         * the depth could be from 2 to 256 from HW spec
         */
        if (!dws->fifo_len) {
                u32 fifo;

                for (fifo = 1; fifo < 256; fifo++) {
                        dw_writel(dws, DW_SPI_TXFTLR, fifo);
                        if (fifo != dw_readl(dws, DW_SPI_TXFTLR))
                                break;
                }
                dw_writel(dws, DW_SPI_TXFTLR, 0);

                dws->fifo_len = (fifo == 1) ? 0 : fifo;
                dev_dbg(dev, "Detected FIFO size: %u bytes\n", dws->fifo_len);
        }

        /*
         * Detect CTRLR0.DFS field size and offset by testing the lowest bits
         * writability. Note DWC SSI controller also has the extended DFS, but
         * with zero offset.
         */
        if (!(dws->caps & DW_SPI_CAP_DWC_SSI)) {
                u32 cr0, tmp = dw_readl(dws, DW_SPI_CTRLR0);

                spi_enable_chip(dws, 0);
                dw_writel(dws, DW_SPI_CTRLR0, 0xffffffff);
                cr0 = dw_readl(dws, DW_SPI_CTRLR0);
                dw_writel(dws, DW_SPI_CTRLR0, tmp);
                spi_enable_chip(dws, 1);

                if (!(cr0 & SPI_DFS_MASK)) {
                        dws->caps |= DW_SPI_CAP_DFS32;
                        dws->dfs_offset = SPI_DFS32_OFFSET;
                        dev_dbg(dev, "Detected 32-bits max data frame size\n");
                }
        } else {
                dws->caps |= DW_SPI_CAP_DFS32;
        }

        /* enable HW fixup for explicit CS deselect for Amazon's alpine chip */
        if (dws->caps & DW_SPI_CAP_CS_OVERRIDE)
                dw_writel(dws, DW_SPI_CS_OVERRIDE, 0xF);
}

int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
{
        struct spi_controller *master;
        int ret;

        if (!dws)
                return -EINVAL;

        master = spi_alloc_master(dev, 0);
        if (!master)
                return -ENOMEM;

        dws->master = master;
        dws->dma_addr = (dma_addr_t)(dws->paddr + DW_SPI_DR);

        spi_controller_set_devdata(master, dws);

        /* Basic HW init */
        spi_hw_init(dev, dws);

        ret = request_irq(dws->irq, dw_spi_irq, IRQF_SHARED, dev_name(dev),
                          master);
        if (ret < 0 && ret != -ENOTCONN) {
                dev_err(dev, "can not get IRQ\n");
                goto err_free_master;
        }

        dw_spi_init_mem_ops(dws);

        master->use_gpio_descriptors = true;
        master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP;
        if (dws->caps & DW_SPI_CAP_DFS32)
                master->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 32);
        else
                master->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 16);
        master->bus_num = dws->bus_num;
        master->num_chipselect = dws->num_cs;
        master->setup = dw_spi_setup;
        master->cleanup = dw_spi_cleanup;
        if (dws->set_cs)
                master->set_cs = dws->set_cs;
        else
                master->set_cs = dw_spi_set_cs;
        master->transfer_one = dw_spi_transfer_one;
        master->handle_err = dw_spi_handle_err;
        if (dws->mem_ops.exec_op)
                master->mem_ops = &dws->mem_ops;
        master->max_speed_hz = dws->max_freq;
        master->dev.of_node = dev->of_node;
        master->dev.fwnode = dev->fwnode;
        master->flags = SPI_MASTER_GPIO_SS;
        master->auto_runtime_pm = true;

        /* Get default rx sample delay */
        device_property_read_u32(dev, "rx-sample-delay-ns",
                                 &dws->def_rx_sample_dly_ns);

        if (dws->dma_ops && dws->dma_ops->dma_init) {
                ret = dws->dma_ops->dma_init(dev, dws);
                if (ret) {
                        dev_warn(dev, "DMA init failed\n");
                } else {
                        master->can_dma = dws->dma_ops->can_dma;
                        master->flags |= SPI_CONTROLLER_MUST_TX;
                }
        }

        ret = spi_register_controller(master);
        if (ret) {
                dev_err(&master->dev, "problem registering spi master\n");
                goto err_dma_exit;
        }

        dw_spi_debugfs_init(dws);
        return 0;

err_dma_exit:
        if (dws->dma_ops && dws->dma_ops->dma_exit)
                dws->dma_ops->dma_exit(dws);
        spi_enable_chip(dws, 0);
        free_irq(dws->irq, master);
err_free_master:
        spi_controller_put(master);
        return ret;
}
EXPORT_SYMBOL_GPL(dw_spi_add_host);

void dw_spi_remove_host(struct dw_spi *dws)
{
        dw_spi_debugfs_remove(dws);

        spi_unregister_controller(dws->master);

        if (dws->dma_ops && dws->dma_ops->dma_exit)
                dws->dma_ops->dma_exit(dws);

        spi_shutdown_chip(dws);

        free_irq(dws->irq, dws->master);
}
EXPORT_SYMBOL_GPL(dw_spi_remove_host);

int dw_spi_suspend_host(struct dw_spi *dws)
{
        int ret;

        ret = spi_controller_suspend(dws->master);
        if (ret)
                return ret;

        spi_shutdown_chip(dws);
        return 0;
}
EXPORT_SYMBOL_GPL(dw_spi_suspend_host);

int dw_spi_resume_host(struct dw_spi *dws)
{
        spi_hw_init(&dws->master->dev, dws);
        return spi_controller_resume(dws->master);
}
EXPORT_SYMBOL_GPL(dw_spi_resume_host);

MODULE_AUTHOR("Feng Tang <feng.tang@intel.com>");
MODULE_DESCRIPTION("Driver for DesignWare SPI controller core");
MODULE_LICENSE("GPL v2");