dmaengine: edma: Use the edma_write_slot instead open coded memcpy_toio

[linux-2.6/btrfs-unstable.git] / drivers / spi / spi-atmel.c

/*
 * Driver for Atmel AT32 and AT91 SPI Controllers
 *
 * Copyright (C) 2006 Atmel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/clk.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/spi/spi.h>
#include <linux/slab.h>
#include <linux/platform_data/dma-atmel.h>
#include <linux/of.h>

#include <linux/io.h>
#include <linux/gpio.h>
#include <linux/pinctrl/consumer.h>
#include <linux/pm_runtime.h>

/* SPI register offsets */
#define SPI_CR                                  0x0000
#define SPI_MR                                  0x0004
#define SPI_RDR                                 0x0008
#define SPI_TDR                                 0x000c
#define SPI_SR                                  0x0010
#define SPI_IER                                 0x0014
#define SPI_IDR                                 0x0018
#define SPI_IMR                                 0x001c
#define SPI_CSR0                                0x0030
#define SPI_CSR1                                0x0034
#define SPI_CSR2                                0x0038
#define SPI_CSR3                                0x003c
#define SPI_FMR                                 0x0040
#define SPI_FLR                                 0x0044
#define SPI_VERSION                             0x00fc
#define SPI_RPR                                 0x0100
#define SPI_RCR                                 0x0104
#define SPI_TPR                                 0x0108
#define SPI_TCR                                 0x010c
#define SPI_RNPR                                0x0110
#define SPI_RNCR                                0x0114
#define SPI_TNPR                                0x0118
#define SPI_TNCR                                0x011c
#define SPI_PTCR                                0x0120
#define SPI_PTSR                                0x0124

/* Bitfields in CR */
#define SPI_SPIEN_OFFSET                        0
#define SPI_SPIEN_SIZE                          1
#define SPI_SPIDIS_OFFSET                       1
#define SPI_SPIDIS_SIZE                         1
#define SPI_SWRST_OFFSET                        7
#define SPI_SWRST_SIZE                          1
#define SPI_LASTXFER_OFFSET                     24
#define SPI_LASTXFER_SIZE                       1
#define SPI_TXFCLR_OFFSET                       16
#define SPI_TXFCLR_SIZE                         1
#define SPI_RXFCLR_OFFSET                       17
#define SPI_RXFCLR_SIZE                         1
#define SPI_FIFOEN_OFFSET                       30
#define SPI_FIFOEN_SIZE                         1
#define SPI_FIFODIS_OFFSET                      31
#define SPI_FIFODIS_SIZE                        1

/* Bitfields in MR */
#define SPI_MSTR_OFFSET                         0
#define SPI_MSTR_SIZE                           1
#define SPI_PS_OFFSET                           1
#define SPI_PS_SIZE                             1
#define SPI_PCSDEC_OFFSET                       2
#define SPI_PCSDEC_SIZE                         1
#define SPI_FDIV_OFFSET                         3
#define SPI_FDIV_SIZE                           1
#define SPI_MODFDIS_OFFSET                      4
#define SPI_MODFDIS_SIZE                        1
#define SPI_WDRBT_OFFSET                        5
#define SPI_WDRBT_SIZE                          1
#define SPI_LLB_OFFSET                          7
#define SPI_LLB_SIZE                            1
#define SPI_PCS_OFFSET                          16
#define SPI_PCS_SIZE                            4
#define SPI_DLYBCS_OFFSET                       24
#define SPI_DLYBCS_SIZE                         8

/* Bitfields in RDR */
#define SPI_RD_OFFSET                           0
#define SPI_RD_SIZE                             16

/* Bitfields in TDR */
#define SPI_TD_OFFSET                           0
#define SPI_TD_SIZE                             16

/* Bitfields in SR */
#define SPI_RDRF_OFFSET                         0
#define SPI_RDRF_SIZE                           1
#define SPI_TDRE_OFFSET                         1
#define SPI_TDRE_SIZE                           1
#define SPI_MODF_OFFSET                         2
#define SPI_MODF_SIZE                           1
#define SPI_OVRES_OFFSET                        3
#define SPI_OVRES_SIZE                          1
#define SPI_ENDRX_OFFSET                        4
#define SPI_ENDRX_SIZE                          1
#define SPI_ENDTX_OFFSET                        5
#define SPI_ENDTX_SIZE                          1
#define SPI_RXBUFF_OFFSET                       6
#define SPI_RXBUFF_SIZE                         1
#define SPI_TXBUFE_OFFSET                       7
#define SPI_TXBUFE_SIZE                         1
#define SPI_NSSR_OFFSET                         8
#define SPI_NSSR_SIZE                           1
#define SPI_TXEMPTY_OFFSET                      9
#define SPI_TXEMPTY_SIZE                        1
#define SPI_SPIENS_OFFSET                       16
#define SPI_SPIENS_SIZE                         1
#define SPI_TXFEF_OFFSET                        24
#define SPI_TXFEF_SIZE                          1
#define SPI_TXFFF_OFFSET                        25
#define SPI_TXFFF_SIZE                          1
#define SPI_TXFTHF_OFFSET                       26
#define SPI_TXFTHF_SIZE                         1
#define SPI_RXFEF_OFFSET                        27
#define SPI_RXFEF_SIZE                          1
#define SPI_RXFFF_OFFSET                        28
#define SPI_RXFFF_SIZE                          1
#define SPI_RXFTHF_OFFSET                       29
#define SPI_RXFTHF_SIZE                         1
#define SPI_TXFPTEF_OFFSET                      30
#define SPI_TXFPTEF_SIZE                        1
#define SPI_RXFPTEF_OFFSET                      31
#define SPI_RXFPTEF_SIZE                        1

/* Bitfields in CSR0 */
#define SPI_CPOL_OFFSET                         0
#define SPI_CPOL_SIZE                           1
#define SPI_NCPHA_OFFSET                        1
#define SPI_NCPHA_SIZE                          1
#define SPI_CSAAT_OFFSET                        3
#define SPI_CSAAT_SIZE                          1
#define SPI_BITS_OFFSET                         4
#define SPI_BITS_SIZE                           4
#define SPI_SCBR_OFFSET                         8
#define SPI_SCBR_SIZE                           8
#define SPI_DLYBS_OFFSET                        16
#define SPI_DLYBS_SIZE                          8
#define SPI_DLYBCT_OFFSET                       24
#define SPI_DLYBCT_SIZE                         8

/* Bitfields in RCR */
#define SPI_RXCTR_OFFSET                        0
#define SPI_RXCTR_SIZE                          16

/* Bitfields in TCR */
#define SPI_TXCTR_OFFSET                        0
#define SPI_TXCTR_SIZE                          16

/* Bitfields in RNCR */
#define SPI_RXNCR_OFFSET                        0
#define SPI_RXNCR_SIZE                          16

/* Bitfields in TNCR */
#define SPI_TXNCR_OFFSET                        0
#define SPI_TXNCR_SIZE                          16

/* Bitfields in PTCR */
#define SPI_RXTEN_OFFSET                        0
#define SPI_RXTEN_SIZE                          1
#define SPI_RXTDIS_OFFSET                       1
#define SPI_RXTDIS_SIZE                         1
#define SPI_TXTEN_OFFSET                        8
#define SPI_TXTEN_SIZE                          1
#define SPI_TXTDIS_OFFSET                       9
#define SPI_TXTDIS_SIZE                         1

/* Bitfields in FMR */
#define SPI_TXRDYM_OFFSET                       0
#define SPI_TXRDYM_SIZE                         2
#define SPI_RXRDYM_OFFSET                       4
#define SPI_RXRDYM_SIZE                         2
#define SPI_TXFTHRES_OFFSET                     16
#define SPI_TXFTHRES_SIZE                       6
#define SPI_RXFTHRES_OFFSET                     24
#define SPI_RXFTHRES_SIZE                       6

/* Bitfields in FLR */
#define SPI_TXFL_OFFSET                         0
#define SPI_TXFL_SIZE                           6
#define SPI_RXFL_OFFSET                         16
#define SPI_RXFL_SIZE                           6

/* Constants for BITS */
#define SPI_BITS_8_BPT                          0
#define SPI_BITS_9_BPT                          1
#define SPI_BITS_10_BPT                         2
#define SPI_BITS_11_BPT                         3
#define SPI_BITS_12_BPT                         4
#define SPI_BITS_13_BPT                         5
#define SPI_BITS_14_BPT                         6
#define SPI_BITS_15_BPT                         7
#define SPI_BITS_16_BPT                         8
#define SPI_ONE_DATA                            0
#define SPI_TWO_DATA                            1
#define SPI_FOUR_DATA                           2

/* Bit manipulation macros */
#define SPI_BIT(name) \
        (1 << SPI_##name##_OFFSET)
#define SPI_BF(name, value) \
        (((value) & ((1 << SPI_##name##_SIZE) - 1)) << SPI_##name##_OFFSET)
#define SPI_BFEXT(name, value) \
        (((value) >> SPI_##name##_OFFSET) & ((1 << SPI_##name##_SIZE) - 1))
#define SPI_BFINS(name, value, old) \
        (((old) & ~(((1 << SPI_##name##_SIZE) - 1) << SPI_##name##_OFFSET)) \
          | SPI_BF(name, value))

/* Register access macros */
#ifdef CONFIG_AVR32
#define spi_readl(port, reg) \
        __raw_readl((port)->regs + SPI_##reg)
#define spi_writel(port, reg, value) \
        __raw_writel((value), (port)->regs + SPI_##reg)

#define spi_readw(port, reg) \
        __raw_readw((port)->regs + SPI_##reg)
#define spi_writew(port, reg, value) \
        __raw_writew((value), (port)->regs + SPI_##reg)

#define spi_readb(port, reg) \
        __raw_readb((port)->regs + SPI_##reg)
#define spi_writeb(port, reg, value) \
        __raw_writeb((value), (port)->regs + SPI_##reg)
#else
#define spi_readl(port, reg) \
        readl_relaxed((port)->regs + SPI_##reg)
#define spi_writel(port, reg, value) \
        writel_relaxed((value), (port)->regs + SPI_##reg)

#define spi_readw(port, reg) \
        readw_relaxed((port)->regs + SPI_##reg)
#define spi_writew(port, reg, value) \
        writew_relaxed((value), (port)->regs + SPI_##reg)

#define spi_readb(port, reg) \
        readb_relaxed((port)->regs + SPI_##reg)
#define spi_writeb(port, reg, value) \
        writeb_relaxed((value), (port)->regs + SPI_##reg)
#endif
/* use PIO for small transfers, avoiding DMA setup/teardown overhead and
 * cache operations; better heuristics consider wordsize and bitrate.
 */
#define DMA_MIN_BYTES   16

#define SPI_DMA_TIMEOUT         (msecs_to_jiffies(1000))

#define AUTOSUSPEND_TIMEOUT     2000

struct atmel_spi_dma {
        struct dma_chan                 *chan_rx;
        struct dma_chan                 *chan_tx;
        struct scatterlist              sgrx;
        struct scatterlist              sgtx;
        struct dma_async_tx_descriptor  *data_desc_rx;
        struct dma_async_tx_descriptor  *data_desc_tx;

        struct at_dma_slave     dma_slave;
};

struct atmel_spi_caps {
        bool    is_spi2;
        bool    has_wdrbt;
        bool    has_dma_support;
};

/*
 * The core SPI transfer engine just talks to a register bank to set up
 * DMA transfers; transfer queue progress is driven by IRQs.  The clock
 * framework provides the base clock, subdivided for each spi_device.
 */
struct atmel_spi {
        spinlock_t              lock;
        unsigned long           flags;

        phys_addr_t             phybase;
        void __iomem            *regs;
        int                     irq;
        struct clk              *clk;
        struct platform_device  *pdev;

        struct spi_transfer     *current_transfer;
        int                     current_remaining_bytes;
        int                     done_status;

        struct completion       xfer_completion;

        /* scratch buffer */
        void                    *buffer;
        dma_addr_t              buffer_dma;

        struct atmel_spi_caps   caps;

        bool                    use_dma;
        bool                    use_pdc;
        bool                    use_cs_gpios;
        /* dmaengine data */
        struct atmel_spi_dma    dma;

        bool                    keep_cs;
        bool                    cs_active;

        u32                     fifo_size;
};

/* Controller-specific per-slave state */
struct atmel_spi_device {
        unsigned int            npcs_pin;
        u32                     csr;
};

#define BUFFER_SIZE             PAGE_SIZE
#define INVALID_DMA_ADDRESS     0xffffffff

/*
 * Version 2 of the SPI controller has
 *  - CR.LASTXFER
 *  - SPI_MR.DIV32 may become FDIV or must-be-zero (here: always zero)
 *  - SPI_SR.TXEMPTY, SPI_SR.NSSR (and corresponding irqs)
 *  - SPI_CSRx.CSAAT
 *  - SPI_CSRx.SBCR allows faster clocking
 */
static bool atmel_spi_is_v2(struct atmel_spi *as)
{
        return as->caps.is_spi2;
}

/*
 * Earlier SPI controllers (e.g. on at91rm9200) have a design bug whereby
 * they assume that spi slave device state will not change on deselect, so
 * that automagic deselection is OK.  ("NPCSx rises if no data is to be
 * transmitted")  Not so!  Workaround uses nCSx pins as GPIOs; or newer
 * controllers have CSAAT and friends.
 *
 * Since the CSAAT functionality is a bit weird on newer controllers as
 * well, we use GPIO to control nCSx pins on all controllers, updating
 * MR.PCS to avoid confusing the controller.  Using GPIOs also lets us
 * support active-high chipselects despite the controller's belief that
 * only active-low devices/systems exists.
 *
 * However, at91rm9200 has a second erratum whereby nCS0 doesn't work
 * right when driven with GPIO.  ("Mode Fault does not allow more than one
 * Master on Chip Select 0.")  No workaround exists for that ... so for
 * nCS0 on that chip, we (a) don't use the GPIO, (b) can't support CS_HIGH,
 * and (c) will trigger that first erratum in some cases.
 */

static void cs_activate(struct atmel_spi *as, struct spi_device *spi)
{
        struct atmel_spi_device *asd = spi->controller_state;
        unsigned active = spi->mode & SPI_CS_HIGH;
        u32 mr;

        if (atmel_spi_is_v2(as)) {
                spi_writel(as, CSR0 + 4 * spi->chip_select, asd->csr);
                /* For the low SPI version, there is a issue that PDC transfer
                 * on CS1,2,3 needs SPI_CSR0.BITS config as SPI_CSR1,2,3.BITS
                 */
                spi_writel(as, CSR0, asd->csr);
                if (as->caps.has_wdrbt) {
                        spi_writel(as, MR,
                                        SPI_BF(PCS, ~(0x01 << spi->chip_select))
                                        | SPI_BIT(WDRBT)
                                        | SPI_BIT(MODFDIS)
                                        | SPI_BIT(MSTR));
                } else {
                        spi_writel(as, MR,
                                        SPI_BF(PCS, ~(0x01 << spi->chip_select))
                                        | SPI_BIT(MODFDIS)
                                        | SPI_BIT(MSTR));
                }

                mr = spi_readl(as, MR);
                if (as->use_cs_gpios)
                        gpio_set_value(asd->npcs_pin, active);
        } else {
                u32 cpol = (spi->mode & SPI_CPOL) ? SPI_BIT(CPOL) : 0;
                int i;
                u32 csr;

                /* Make sure clock polarity is correct */
                for (i = 0; i < spi->master->num_chipselect; i++) {
                        csr = spi_readl(as, CSR0 + 4 * i);
                        if ((csr ^ cpol) & SPI_BIT(CPOL))
                                spi_writel(as, CSR0 + 4 * i,
                                                csr ^ SPI_BIT(CPOL));
                }

                mr = spi_readl(as, MR);
                mr = SPI_BFINS(PCS, ~(1 << spi->chip_select), mr);
                if (as->use_cs_gpios && spi->chip_select != 0)
                        gpio_set_value(asd->npcs_pin, active);
                spi_writel(as, MR, mr);
        }

        dev_dbg(&spi->dev, "activate %u%s, mr %08x\n",
                        asd->npcs_pin, active ? " (high)" : "",
                        mr);
}

static void cs_deactivate(struct atmel_spi *as, struct spi_device *spi)
{
        struct atmel_spi_device *asd = spi->controller_state;
        unsigned active = spi->mode & SPI_CS_HIGH;
        u32 mr;

        /* only deactivate *this* device; sometimes transfers to
         * another device may be active when this routine is called.
         */
        mr = spi_readl(as, MR);
        if (~SPI_BFEXT(PCS, mr) & (1 << spi->chip_select)) {
                mr = SPI_BFINS(PCS, 0xf, mr);
                spi_writel(as, MR, mr);
        }

        dev_dbg(&spi->dev, "DEactivate %u%s, mr %08x\n",
                        asd->npcs_pin, active ? " (low)" : "",
                        mr);

        if (!as->use_cs_gpios)
                spi_writel(as, CR, SPI_BIT(LASTXFER));
        else if (atmel_spi_is_v2(as) || spi->chip_select != 0)
                gpio_set_value(asd->npcs_pin, !active);
}

static void atmel_spi_lock(struct atmel_spi *as) __acquires(&as->lock)
{
        spin_lock_irqsave(&as->lock, as->flags);
}

static void atmel_spi_unlock(struct atmel_spi *as) __releases(&as->lock)
{
        spin_unlock_irqrestore(&as->lock, as->flags);
}

static inline bool atmel_spi_use_dma(struct atmel_spi *as,
                                struct spi_transfer *xfer)
{
        return as->use_dma && xfer->len >= DMA_MIN_BYTES;
}

static int atmel_spi_dma_slave_config(struct atmel_spi *as,
                                struct dma_slave_config *slave_config,
                                u8 bits_per_word)
{
        int err = 0;

        if (bits_per_word > 8) {
                slave_config->dst_addr_width = DMA_SLAVE_BUSWIDTH_2_BYTES;
                slave_config->src_addr_width = DMA_SLAVE_BUSWIDTH_2_BYTES;
        } else {
                slave_config->dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
                slave_config->src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
        }

        slave_config->dst_addr = (dma_addr_t)as->phybase + SPI_TDR;
        slave_config->src_addr = (dma_addr_t)as->phybase + SPI_RDR;
        slave_config->src_maxburst = 1;
        slave_config->dst_maxburst = 1;
        slave_config->device_fc = false;

        /*
         * This driver uses fixed peripheral select mode (PS bit set to '0' in
         * the Mode Register).
         * So according to the datasheet, when FIFOs are available (and
         * enabled), the Transmit FIFO operates in Multiple Data Mode.
         * In this mode, up to 2 data, not 4, can be written into the Transmit
         * Data Register in a single access.
         * However, the first data has to be written into the lowest 16 bits and
         * the second data into the highest 16 bits of the Transmit
         * Data Register. For 8bit data (the most frequent case), it would
         * require to rework tx_buf so each data would actualy fit 16 bits.
         * So we'd rather write only one data at the time. Hence the transmit
         * path works the same whether FIFOs are available (and enabled) or not.
         */
        slave_config->direction = DMA_MEM_TO_DEV;
        if (dmaengine_slave_config(as->dma.chan_tx, slave_config)) {
                dev_err(&as->pdev->dev,
                        "failed to configure tx dma channel\n");
                err = -EINVAL;
        }

        /*
         * This driver configures the spi controller for master mode (MSTR bit
         * set to '1' in the Mode Register).
         * So according to the datasheet, when FIFOs are available (and
         * enabled), the Receive FIFO operates in Single Data Mode.
         * So the receive path works the same whether FIFOs are available (and
         * enabled) or not.
         */
        slave_config->direction = DMA_DEV_TO_MEM;
        if (dmaengine_slave_config(as->dma.chan_rx, slave_config)) {
                dev_err(&as->pdev->dev,
                        "failed to configure rx dma channel\n");
                err = -EINVAL;
        }

        return err;
}

static int atmel_spi_configure_dma(struct atmel_spi *as)
{
        struct dma_slave_config slave_config;
        struct device *dev = &as->pdev->dev;
        int err;

        dma_cap_mask_t mask;
        dma_cap_zero(mask);
        dma_cap_set(DMA_SLAVE, mask);

        as->dma.chan_tx = dma_request_slave_channel_reason(dev, "tx");
        if (IS_ERR(as->dma.chan_tx)) {
                err = PTR_ERR(as->dma.chan_tx);
                if (err == -EPROBE_DEFER) {
                        dev_warn(dev, "no DMA channel available at the moment\n");
                        return err;
                }
                dev_err(dev,
                        "DMA TX channel not available, SPI unable to use DMA\n");
                err = -EBUSY;
                goto error;
        }

        /*
         * No reason to check EPROBE_DEFER here since we have already requested
         * tx channel. If it fails here, it's for another reason.
         */
        as->dma.chan_rx = dma_request_slave_channel(dev, "rx");

        if (!as->dma.chan_rx) {
                dev_err(dev,
                        "DMA RX channel not available, SPI unable to use DMA\n");
                err = -EBUSY;
                goto error;
        }

        err = atmel_spi_dma_slave_config(as, &slave_config, 8);
        if (err)
                goto error;

        dev_info(&as->pdev->dev,
                        "Using %s (tx) and %s (rx) for DMA transfers\n",
                        dma_chan_name(as->dma.chan_tx),
                        dma_chan_name(as->dma.chan_rx));
        return 0;
error:
        if (as->dma.chan_rx)
                dma_release_channel(as->dma.chan_rx);
        if (!IS_ERR(as->dma.chan_tx))
                dma_release_channel(as->dma.chan_tx);
        return err;
}

static void atmel_spi_stop_dma(struct atmel_spi *as)
{
        if (as->dma.chan_rx)
                dmaengine_terminate_all(as->dma.chan_rx);
        if (as->dma.chan_tx)
                dmaengine_terminate_all(as->dma.chan_tx);
}

static void atmel_spi_release_dma(struct atmel_spi *as)
{
        if (as->dma.chan_rx)
                dma_release_channel(as->dma.chan_rx);
        if (as->dma.chan_tx)
                dma_release_channel(as->dma.chan_tx);
}

/* This function is called by the DMA driver from tasklet context */
static void dma_callback(void *data)
{
        struct spi_master       *master = data;
        struct atmel_spi        *as = spi_master_get_devdata(master);

        complete(&as->xfer_completion);
}

/*
 * Next transfer using PIO without FIFO.
 */
static void atmel_spi_next_xfer_single(struct spi_master *master,
                                       struct spi_transfer *xfer)
{
        struct atmel_spi        *as = spi_master_get_devdata(master);
        unsigned long xfer_pos = xfer->len - as->current_remaining_bytes;

        dev_vdbg(master->dev.parent, "atmel_spi_next_xfer_pio\n");

        /* Make sure data is not remaining in RDR */
        spi_readl(as, RDR);
        while (spi_readl(as, SR) & SPI_BIT(RDRF)) {
                spi_readl(as, RDR);
                cpu_relax();
        }

        if (xfer->tx_buf) {
                if (xfer->bits_per_word > 8)
                        spi_writel(as, TDR, *(u16 *)(xfer->tx_buf + xfer_pos));
                else
                        spi_writel(as, TDR, *(u8 *)(xfer->tx_buf + xfer_pos));
        } else {
                spi_writel(as, TDR, 0);
        }

        dev_dbg(master->dev.parent,
                "  start pio xfer %p: len %u tx %p rx %p bitpw %d\n",
                xfer, xfer->len, xfer->tx_buf, xfer->rx_buf,
                xfer->bits_per_word);

        /* Enable relevant interrupts */
        spi_writel(as, IER, SPI_BIT(RDRF) | SPI_BIT(OVRES));
}

/*
 * Next transfer using PIO with FIFO.
 */
static void atmel_spi_next_xfer_fifo(struct spi_master *master,
                                     struct spi_transfer *xfer)
{
        struct atmel_spi *as = spi_master_get_devdata(master);
        u32 current_remaining_data, num_data;
        u32 offset = xfer->len - as->current_remaining_bytes;
        const u16 *words = (const u16 *)((u8 *)xfer->tx_buf + offset);
        const u8  *bytes = (const u8  *)((u8 *)xfer->tx_buf + offset);
        u16 td0, td1;
        u32 fifomr;

        dev_vdbg(master->dev.parent, "atmel_spi_next_xfer_fifo\n");

        /* Compute the number of data to transfer in the current iteration */
        current_remaining_data = ((xfer->bits_per_word > 8) ?
                                  ((u32)as->current_remaining_bytes >> 1) :
                                  (u32)as->current_remaining_bytes);
        num_data = min(current_remaining_data, as->fifo_size);

        /* Flush RX and TX FIFOs */
        spi_writel(as, CR, SPI_BIT(RXFCLR) | SPI_BIT(TXFCLR));
        while (spi_readl(as, FLR))
                cpu_relax();

        /* Set RX FIFO Threshold to the number of data to transfer */
        fifomr = spi_readl(as, FMR);
        spi_writel(as, FMR, SPI_BFINS(RXFTHRES, num_data, fifomr));

        /* Clear FIFO flags in the Status Register, especially RXFTHF */
        (void)spi_readl(as, SR);

        /* Fill TX FIFO */
        while (num_data >= 2) {
                if (xfer->tx_buf) {
                        if (xfer->bits_per_word > 8) {
                                td0 = *words++;
                                td1 = *words++;
                        } else {
                                td0 = *bytes++;
                                td1 = *bytes++;
                        }
                } else {
                        td0 = 0;
                        td1 = 0;
                }

                spi_writel(as, TDR, (td1 << 16) | td0);
                num_data -= 2;
        }

        if (num_data) {
                if (xfer->tx_buf) {
                        if (xfer->bits_per_word > 8)
                                td0 = *words++;
                        else
                                td0 = *bytes++;
                } else {
                        td0 = 0;
                }

                spi_writew(as, TDR, td0);
                num_data--;
        }

        dev_dbg(master->dev.parent,
                "  start fifo xfer %p: len %u tx %p rx %p bitpw %d\n",
                xfer, xfer->len, xfer->tx_buf, xfer->rx_buf,
                xfer->bits_per_word);

        /*
         * Enable RX FIFO Threshold Flag interrupt to be notified about
         * transfer completion.
         */
        spi_writel(as, IER, SPI_BIT(RXFTHF) | SPI_BIT(OVRES));
}

/*
 * Next transfer using PIO.
 */
static void atmel_spi_next_xfer_pio(struct spi_master *master,
                                    struct spi_transfer *xfer)
{
        struct atmel_spi *as = spi_master_get_devdata(master);

        if (as->fifo_size)
                atmel_spi_next_xfer_fifo(master, xfer);
        else
                atmel_spi_next_xfer_single(master, xfer);
}

/*
 * Submit next transfer for DMA.
 */
static int atmel_spi_next_xfer_dma_submit(struct spi_master *master,
                                struct spi_transfer *xfer,
                                u32 *plen)
{
        struct atmel_spi        *as = spi_master_get_devdata(master);
        struct dma_chan         *rxchan = as->dma.chan_rx;
        struct dma_chan         *txchan = as->dma.chan_tx;
        struct dma_async_tx_descriptor *rxdesc;
        struct dma_async_tx_descriptor *txdesc;
        struct dma_slave_config slave_config;
        dma_cookie_t            cookie;
        u32     len = *plen;

        dev_vdbg(master->dev.parent, "atmel_spi_next_xfer_dma_submit\n");

        /* Check that the channels are available */
        if (!rxchan || !txchan)
                return -ENODEV;

        /* release lock for DMA operations */
        atmel_spi_unlock(as);

        /* prepare the RX dma transfer */
        sg_init_table(&as->dma.sgrx, 1);
        if (xfer->rx_buf) {
                as->dma.sgrx.dma_address = xfer->rx_dma + xfer->len - *plen;
        } else {
                as->dma.sgrx.dma_address = as->buffer_dma;
                if (len > BUFFER_SIZE)
                        len = BUFFER_SIZE;
        }

        /* prepare the TX dma transfer */
        sg_init_table(&as->dma.sgtx, 1);
        if (xfer->tx_buf) {
                as->dma.sgtx.dma_address = xfer->tx_dma + xfer->len - *plen;
        } else {
                as->dma.sgtx.dma_address = as->buffer_dma;
                if (len > BUFFER_SIZE)
                        len = BUFFER_SIZE;
                memset(as->buffer, 0, len);
        }

        sg_dma_len(&as->dma.sgtx) = len;
        sg_dma_len(&as->dma.sgrx) = len;

        *plen = len;

        if (atmel_spi_dma_slave_config(as, &slave_config, 8))
                goto err_exit;

        /* Send both scatterlists */
        rxdesc = dmaengine_prep_slave_sg(rxchan, &as->dma.sgrx, 1,
                                         DMA_FROM_DEVICE,
                                         DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!rxdesc)
                goto err_dma;

        txdesc = dmaengine_prep_slave_sg(txchan, &as->dma.sgtx, 1,
                                         DMA_TO_DEVICE,
                                         DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!txdesc)
                goto err_dma;

        dev_dbg(master->dev.parent,
                "  start dma xfer %p: len %u tx %p/%08llx rx %p/%08llx\n",
                xfer, xfer->len, xfer->tx_buf, (unsigned long long)xfer->tx_dma,
                xfer->rx_buf, (unsigned long long)xfer->rx_dma);

        /* Enable relevant interrupts */
        spi_writel(as, IER, SPI_BIT(OVRES));

        /* Put the callback on the RX transfer only, that should finish last */
        rxdesc->callback = dma_callback;
        rxdesc->callback_param = master;

        /* Submit and fire RX and TX with TX last so we're ready to read! */
        cookie = rxdesc->tx_submit(rxdesc);
        if (dma_submit_error(cookie))
                goto err_dma;
        cookie = txdesc->tx_submit(txdesc);
        if (dma_submit_error(cookie))
                goto err_dma;
        rxchan->device->device_issue_pending(rxchan);
        txchan->device->device_issue_pending(txchan);

        /* take back lock */
        atmel_spi_lock(as);
        return 0;

err_dma:
        spi_writel(as, IDR, SPI_BIT(OVRES));
        atmel_spi_stop_dma(as);
err_exit:
        atmel_spi_lock(as);
        return -ENOMEM;
}

static void atmel_spi_next_xfer_data(struct spi_master *master,
                                struct spi_transfer *xfer,
                                dma_addr_t *tx_dma,
                                dma_addr_t *rx_dma,
                                u32 *plen)
{
        struct atmel_spi        *as = spi_master_get_devdata(master);
        u32                     len = *plen;

        /* use scratch buffer only when rx or tx data is unspecified */
        if (xfer->rx_buf)
                *rx_dma = xfer->rx_dma + xfer->len - *plen;
        else {
                *rx_dma = as->buffer_dma;
                if (len > BUFFER_SIZE)
                        len = BUFFER_SIZE;
        }

        if (xfer->tx_buf)
                *tx_dma = xfer->tx_dma + xfer->len - *plen;
        else {
                *tx_dma = as->buffer_dma;
                if (len > BUFFER_SIZE)
                        len = BUFFER_SIZE;
                memset(as->buffer, 0, len);
                dma_sync_single_for_device(&as->pdev->dev,
                                as->buffer_dma, len, DMA_TO_DEVICE);
        }

        *plen = len;
}

static int atmel_spi_set_xfer_speed(struct atmel_spi *as,
                                    struct spi_device *spi,
                                    struct spi_transfer *xfer)
{
        u32                     scbr, csr;
        unsigned long           bus_hz;

        /* v1 chips start out at half the peripheral bus speed. */
        bus_hz = clk_get_rate(as->clk);
        if (!atmel_spi_is_v2(as))
                bus_hz /= 2;

        /*
         * Calculate the lowest divider that satisfies the
         * constraint, assuming div32/fdiv/mbz == 0.
         */
        if (xfer->speed_hz)
                scbr = DIV_ROUND_UP(bus_hz, xfer->speed_hz);
        else
                /*
                 * This can happend if max_speed is null.
                 * In this case, we set the lowest possible speed
                 */
                scbr = 0xff;

        /*
         * If the resulting divider doesn't fit into the
         * register bitfield, we can't satisfy the constraint.
         */
        if (scbr >= (1 << SPI_SCBR_SIZE)) {
                dev_err(&spi->dev,
                        "setup: %d Hz too slow, scbr %u; min %ld Hz\n",
                        xfer->speed_hz, scbr, bus_hz/255);
                return -EINVAL;
        }
        if (scbr == 0) {
                dev_err(&spi->dev,
                        "setup: %d Hz too high, scbr %u; max %ld Hz\n",
                        xfer->speed_hz, scbr, bus_hz);
                return -EINVAL;
        }
        csr = spi_readl(as, CSR0 + 4 * spi->chip_select);
        csr = SPI_BFINS(SCBR, scbr, csr);
        spi_writel(as, CSR0 + 4 * spi->chip_select, csr);

        return 0;
}

/*
 * Submit next transfer for PDC.
 * lock is held, spi irq is blocked
 */
static void atmel_spi_pdc_next_xfer(struct spi_master *master,
                                        struct spi_message *msg,
                                        struct spi_transfer *xfer)
{
        struct atmel_spi        *as = spi_master_get_devdata(master);
        u32                     len;
        dma_addr_t              tx_dma, rx_dma;

        spi_writel(as, PTCR, SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS));

        len = as->current_remaining_bytes;
        atmel_spi_next_xfer_data(master, xfer, &tx_dma, &rx_dma, &len);
        as->current_remaining_bytes -= len;

        spi_writel(as, RPR, rx_dma);
        spi_writel(as, TPR, tx_dma);

        if (msg->spi->bits_per_word > 8)
                len >>= 1;
        spi_writel(as, RCR, len);
        spi_writel(as, TCR, len);

        dev_dbg(&msg->spi->dev,
                "  start xfer %p: len %u tx %p/%08llx rx %p/%08llx\n",
                xfer, xfer->len, xfer->tx_buf,
                (unsigned long long)xfer->tx_dma, xfer->rx_buf,
                (unsigned long long)xfer->rx_dma);

        if (as->current_remaining_bytes) {
                len = as->current_remaining_bytes;
                atmel_spi_next_xfer_data(master, xfer, &tx_dma, &rx_dma, &len);
                as->current_remaining_bytes -= len;

                spi_writel(as, RNPR, rx_dma);
                spi_writel(as, TNPR, tx_dma);

                if (msg->spi->bits_per_word > 8)
                        len >>= 1;
                spi_writel(as, RNCR, len);
                spi_writel(as, TNCR, len);

                dev_dbg(&msg->spi->dev,
                        "  next xfer %p: len %u tx %p/%08llx rx %p/%08llx\n",
                        xfer, xfer->len, xfer->tx_buf,
                        (unsigned long long)xfer->tx_dma, xfer->rx_buf,
                        (unsigned long long)xfer->rx_dma);
        }

        /* REVISIT: We're waiting for RXBUFF before we start the next
         * transfer because we need to handle some difficult timing
         * issues otherwise. If we wait for TXBUFE in one transfer and
         * then starts waiting for RXBUFF in the next, it's difficult
         * to tell the difference between the RXBUFF interrupt we're
         * actually waiting for and the RXBUFF interrupt of the
         * previous transfer.
         *
         * It should be doable, though. Just not now...
         */
        spi_writel(as, IER, SPI_BIT(RXBUFF) | SPI_BIT(OVRES));
        spi_writel(as, PTCR, SPI_BIT(TXTEN) | SPI_BIT(RXTEN));
}

/*
 * For DMA, tx_buf/tx_dma have the same relationship as rx_buf/rx_dma:
 *  - The buffer is either valid for CPU access, else NULL
 *  - If the buffer is valid, so is its DMA address
 *
 * This driver manages the dma address unless message->is_dma_mapped.
 */
static int
atmel_spi_dma_map_xfer(struct atmel_spi *as, struct spi_transfer *xfer)
{
        struct device   *dev = &as->pdev->dev;

        xfer->tx_dma = xfer->rx_dma = INVALID_DMA_ADDRESS;
        if (xfer->tx_buf) {
                /* tx_buf is a const void* where we need a void * for the dma
                 * mapping */
                void *nonconst_tx = (void *)xfer->tx_buf;

                xfer->tx_dma = dma_map_single(dev,
                                nonconst_tx, xfer->len,
                                DMA_TO_DEVICE);
                if (dma_mapping_error(dev, xfer->tx_dma))
                        return -ENOMEM;
        }
        if (xfer->rx_buf) {
                xfer->rx_dma = dma_map_single(dev,
                                xfer->rx_buf, xfer->len,
                                DMA_FROM_DEVICE);
                if (dma_mapping_error(dev, xfer->rx_dma)) {
                        if (xfer->tx_buf)
                                dma_unmap_single(dev,
                                                xfer->tx_dma, xfer->len,
                                                DMA_TO_DEVICE);
                        return -ENOMEM;
                }
        }
        return 0;
}

static void atmel_spi_dma_unmap_xfer(struct spi_master *master,
                                     struct spi_transfer *xfer)
{
        if (xfer->tx_dma != INVALID_DMA_ADDRESS)
                dma_unmap_single(master->dev.parent, xfer->tx_dma,
                                 xfer->len, DMA_TO_DEVICE);
        if (xfer->rx_dma != INVALID_DMA_ADDRESS)
                dma_unmap_single(master->dev.parent, xfer->rx_dma,
                                 xfer->len, DMA_FROM_DEVICE);
}

static void atmel_spi_disable_pdc_transfer(struct atmel_spi *as)
{
        spi_writel(as, PTCR, SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS));
}

static void
atmel_spi_pump_single_data(struct atmel_spi *as, struct spi_transfer *xfer)
{
        u8              *rxp;
        u16             *rxp16;
        unsigned long   xfer_pos = xfer->len - as->current_remaining_bytes;

        if (xfer->rx_buf) {
                if (xfer->bits_per_word > 8) {
                        rxp16 = (u16 *)(((u8 *)xfer->rx_buf) + xfer_pos);
                        *rxp16 = spi_readl(as, RDR);
                } else {
                        rxp = ((u8 *)xfer->rx_buf) + xfer_pos;
                        *rxp = spi_readl(as, RDR);
                }
        } else {
                spi_readl(as, RDR);
        }
        if (xfer->bits_per_word > 8) {
                if (as->current_remaining_bytes > 2)
                        as->current_remaining_bytes -= 2;
                else
                        as->current_remaining_bytes = 0;
        } else {
                as->current_remaining_bytes--;
        }
}

static void
atmel_spi_pump_fifo_data(struct atmel_spi *as, struct spi_transfer *xfer)
{
        u32 fifolr = spi_readl(as, FLR);
        u32 num_bytes, num_data = SPI_BFEXT(RXFL, fifolr);
        u32 offset = xfer->len - as->current_remaining_bytes;
        u16 *words = (u16 *)((u8 *)xfer->rx_buf + offset);
        u8  *bytes = (u8  *)((u8 *)xfer->rx_buf + offset);
        u16 rd; /* RD field is the lowest 16 bits of RDR */

        /* Update the number of remaining bytes to transfer */
        num_bytes = ((xfer->bits_per_word > 8) ?
                     (num_data << 1) :
                     num_data);

        if (as->current_remaining_bytes > num_bytes)
                as->current_remaining_bytes -= num_bytes;
        else
                as->current_remaining_bytes = 0;

        /* Handle odd number of bytes when data are more than 8bit width */
        if (xfer->bits_per_word > 8)
                as->current_remaining_bytes &= ~0x1;

        /* Read data */
        while (num_data) {
                rd = spi_readl(as, RDR);
                if (xfer->rx_buf) {
                        if (xfer->bits_per_word > 8)
                                *words++ = rd;
                        else
                                *bytes++ = rd;
                }
                num_data--;
        }
}

/* Called from IRQ
 *
 * Must update "current_remaining_bytes" to keep track of data
 * to transfer.
 */
static void
atmel_spi_pump_pio_data(struct atmel_spi *as, struct spi_transfer *xfer)
{
        if (as->fifo_size)
                atmel_spi_pump_fifo_data(as, xfer);
        else
                atmel_spi_pump_single_data(as, xfer);
}

/* Interrupt
 *
 * No need for locking in this Interrupt handler: done_status is the
 * only information modified.
 */
static irqreturn_t
atmel_spi_pio_interrupt(int irq, void *dev_id)
{
        struct spi_master       *master = dev_id;
        struct atmel_spi        *as = spi_master_get_devdata(master);
        u32                     status, pending, imr;
        struct spi_transfer     *xfer;
        int                     ret = IRQ_NONE;

        imr = spi_readl(as, IMR);
        status = spi_readl(as, SR);
        pending = status & imr;

        if (pending & SPI_BIT(OVRES)) {
                ret = IRQ_HANDLED;
                spi_writel(as, IDR, SPI_BIT(OVRES));
                dev_warn(master->dev.parent, "overrun\n");

                /*
                 * When we get an overrun, we disregard the current
                 * transfer. Data will not be copied back from any
                 * bounce buffer and msg->actual_len will not be
                 * updated with the last xfer.
                 *
                 * We will also not process any remaning transfers in
                 * the message.
                 */
                as->done_status = -EIO;
                smp_wmb();

                /* Clear any overrun happening while cleaning up */
                spi_readl(as, SR);

                complete(&as->xfer_completion);

        } else if (pending & (SPI_BIT(RDRF) | SPI_BIT(RXFTHF))) {
                atmel_spi_lock(as);

                if (as->current_remaining_bytes) {
                        ret = IRQ_HANDLED;
                        xfer = as->current_transfer;
                        atmel_spi_pump_pio_data(as, xfer);
                        if (!as->current_remaining_bytes)
                                spi_writel(as, IDR, pending);

                        complete(&as->xfer_completion);
                }

                atmel_spi_unlock(as);
        } else {
                WARN_ONCE(pending, "IRQ not handled, pending = %x\n", pending);
                ret = IRQ_HANDLED;
                spi_writel(as, IDR, pending);
        }

        return ret;
}

static irqreturn_t
atmel_spi_pdc_interrupt(int irq, void *dev_id)
{
        struct spi_master       *master = dev_id;
        struct atmel_spi        *as = spi_master_get_devdata(master);
        u32                     status, pending, imr;
        int                     ret = IRQ_NONE;

        imr = spi_readl(as, IMR);
        status = spi_readl(as, SR);
        pending = status & imr;

        if (pending & SPI_BIT(OVRES)) {

                ret = IRQ_HANDLED;

                spi_writel(as, IDR, (SPI_BIT(RXBUFF) | SPI_BIT(ENDRX)
                                     | SPI_BIT(OVRES)));

                /* Clear any overrun happening while cleaning up */
                spi_readl(as, SR);

                as->done_status = -EIO;

                complete(&as->xfer_completion);

        } else if (pending & (SPI_BIT(RXBUFF) | SPI_BIT(ENDRX))) {
                ret = IRQ_HANDLED;

                spi_writel(as, IDR, pending);

                complete(&as->xfer_completion);
        }

        return ret;
}

static int atmel_spi_setup(struct spi_device *spi)
{
        struct atmel_spi        *as;
        struct atmel_spi_device *asd;
        u32                     csr;
        unsigned int            bits = spi->bits_per_word;
        unsigned int            npcs_pin;
        int                     ret;

        as = spi_master_get_devdata(spi->master);

        /* see notes above re chipselect */
        if (!atmel_spi_is_v2(as)
                        && spi->chip_select == 0
                        && (spi->mode & SPI_CS_HIGH)) {
                dev_dbg(&spi->dev, "setup: can't be active-high\n");
                return -EINVAL;
        }

        csr = SPI_BF(BITS, bits - 8);
        if (spi->mode & SPI_CPOL)
                csr |= SPI_BIT(CPOL);
        if (!(spi->mode & SPI_CPHA))
                csr |= SPI_BIT(NCPHA);
        if (!as->use_cs_gpios)
                csr |= SPI_BIT(CSAAT);

        /* DLYBS is mostly irrelevant since we manage chipselect using GPIOs.
         *
         * DLYBCT would add delays between words, slowing down transfers.
         * It could potentially be useful to cope with DMA bottlenecks, but
         * in those cases it's probably best to just use a lower bitrate.
         */
        csr |= SPI_BF(DLYBS, 0);
        csr |= SPI_BF(DLYBCT, 0);

        /* chipselect must have been muxed as GPIO (e.g. in board setup) */
        npcs_pin = (unsigned long)spi->controller_data;

        if (!as->use_cs_gpios)
                npcs_pin = spi->chip_select;
        else if (gpio_is_valid(spi->cs_gpio))
                npcs_pin = spi->cs_gpio;

        asd = spi->controller_state;
        if (!asd) {
                asd = kzalloc(sizeof(struct atmel_spi_device), GFP_KERNEL);
                if (!asd)
                        return -ENOMEM;

                if (as->use_cs_gpios) {
                        ret = gpio_request(npcs_pin, dev_name(&spi->dev));
                        if (ret) {
                                kfree(asd);
                                return ret;
                        }

                        gpio_direction_output(npcs_pin,
                                              !(spi->mode & SPI_CS_HIGH));
                }

                asd->npcs_pin = npcs_pin;
                spi->controller_state = asd;
        }

        asd->csr = csr;

        dev_dbg(&spi->dev,
                "setup: bpw %u mode 0x%x -> csr%d %08x\n",
                bits, spi->mode, spi->chip_select, csr);

        if (!atmel_spi_is_v2(as))
                spi_writel(as, CSR0 + 4 * spi->chip_select, csr);

        return 0;
}

static int atmel_spi_one_transfer(struct spi_master *master,
                                        struct spi_message *msg,
                                        struct spi_transfer *xfer)
{
        struct atmel_spi        *as;
        struct spi_device       *spi = msg->spi;
        u8                      bits;
        u32                     len;
        struct atmel_spi_device *asd;
        int                     timeout;
        int                     ret;
        unsigned long           dma_timeout;

        as = spi_master_get_devdata(master);

        if (!(xfer->tx_buf || xfer->rx_buf) && xfer->len) {
                dev_dbg(&spi->dev, "missing rx or tx buf\n");
                return -EINVAL;
        }

        if (xfer->bits_per_word) {
                asd = spi->controller_state;
                bits = (asd->csr >> 4) & 0xf;
                if (bits != xfer->bits_per_word - 8) {
                        dev_dbg(&spi->dev,
                        "you can't yet change bits_per_word in transfers\n");
                        return -ENOPROTOOPT;
                }
        }

        /*
         * DMA map early, for performance (empties dcache ASAP) and
         * better fault reporting.
         */
        if ((!msg->is_dma_mapped)
                && (atmel_spi_use_dma(as, xfer) || as->use_pdc)) {
                if (atmel_spi_dma_map_xfer(as, xfer) < 0)
                        return -ENOMEM;
        }

        atmel_spi_set_xfer_speed(as, msg->spi, xfer);

        as->done_status = 0;
        as->current_transfer = xfer;
        as->current_remaining_bytes = xfer->len;
        while (as->current_remaining_bytes) {
                reinit_completion(&as->xfer_completion);

                if (as->use_pdc) {
                        atmel_spi_pdc_next_xfer(master, msg, xfer);
                } else if (atmel_spi_use_dma(as, xfer)) {
                        len = as->current_remaining_bytes;
                        ret = atmel_spi_next_xfer_dma_submit(master,
                                                                xfer, &len);
                        if (ret) {
                                dev_err(&spi->dev,
                                        "unable to use DMA, fallback to PIO\n");
                                atmel_spi_next_xfer_pio(master, xfer);
                        } else {
                                as->current_remaining_bytes -= len;
                                if (as->current_remaining_bytes < 0)
                                        as->current_remaining_bytes = 0;
                        }
                } else {
                        atmel_spi_next_xfer_pio(master, xfer);
                }

                /* interrupts are disabled, so free the lock for schedule */
                atmel_spi_unlock(as);
                dma_timeout = wait_for_completion_timeout(&as->xfer_completion,
                                                          SPI_DMA_TIMEOUT);
                atmel_spi_lock(as);
                if (WARN_ON(dma_timeout == 0)) {
                        dev_err(&spi->dev, "spi transfer timeout\n");
                        as->done_status = -EIO;
                }

                if (as->done_status)
                        break;
        }

        if (as->done_status) {
                if (as->use_pdc) {
                        dev_warn(master->dev.parent,
                                "overrun (%u/%u remaining)\n",
                                spi_readl(as, TCR), spi_readl(as, RCR));

                        /*
                         * Clean up DMA registers and make sure the data
                         * registers are empty.
                         */
                        spi_writel(as, RNCR, 0);
                        spi_writel(as, TNCR, 0);
                        spi_writel(as, RCR, 0);
                        spi_writel(as, TCR, 0);
                        for (timeout = 1000; timeout; timeout--)
                                if (spi_readl(as, SR) & SPI_BIT(TXEMPTY))
                                        break;
                        if (!timeout)
                                dev_warn(master->dev.parent,
                                         "timeout waiting for TXEMPTY");
                        while (spi_readl(as, SR) & SPI_BIT(RDRF))
                                spi_readl(as, RDR);

                        /* Clear any overrun happening while cleaning up */
                        spi_readl(as, SR);

                } else if (atmel_spi_use_dma(as, xfer)) {
                        atmel_spi_stop_dma(as);
                }

                if (!msg->is_dma_mapped
                        && (atmel_spi_use_dma(as, xfer) || as->use_pdc))
                        atmel_spi_dma_unmap_xfer(master, xfer);

                return 0;

        } else {
                /* only update length if no error */
                msg->actual_length += xfer->len;
        }

        if (!msg->is_dma_mapped
                && (atmel_spi_use_dma(as, xfer) || as->use_pdc))
                atmel_spi_dma_unmap_xfer(master, xfer);

        if (xfer->delay_usecs)
                udelay(xfer->delay_usecs);

        if (xfer->cs_change) {
                if (list_is_last(&xfer->transfer_list,
                                 &msg->transfers)) {
                        as->keep_cs = true;
                } else {
                        as->cs_active = !as->cs_active;
                        if (as->cs_active)
                                cs_activate(as, msg->spi);
                        else
                                cs_deactivate(as, msg->spi);
                }
        }

        return 0;
}

static int atmel_spi_transfer_one_message(struct spi_master *master,
                                                struct spi_message *msg)
{
        struct atmel_spi *as;
        struct spi_transfer *xfer;
        struct spi_device *spi = msg->spi;
        int ret = 0;

        as = spi_master_get_devdata(master);

        dev_dbg(&spi->dev, "new message %p submitted for %s\n",
                                        msg, dev_name(&spi->dev));

        atmel_spi_lock(as);
        cs_activate(as, spi);

        as->cs_active = true;
        as->keep_cs = false;

        msg->status = 0;
        msg->actual_length = 0;

        list_for_each_entry(xfer, &msg->transfers, transfer_list) {
                ret = atmel_spi_one_transfer(master, msg, xfer);
                if (ret)
                        goto msg_done;
        }

        if (as->use_pdc)
                atmel_spi_disable_pdc_transfer(as);

        list_for_each_entry(xfer, &msg->transfers, transfer_list) {
                dev_dbg(&spi->dev,
                        "  xfer %p: len %u tx %p/%pad rx %p/%pad\n",
                        xfer, xfer->len,
                        xfer->tx_buf, &xfer->tx_dma,
                        xfer->rx_buf, &xfer->rx_dma);
        }

msg_done:
        if (!as->keep_cs)
                cs_deactivate(as, msg->spi);

        atmel_spi_unlock(as);

        msg->status = as->done_status;
        spi_finalize_current_message(spi->master);

        return ret;
}

static void atmel_spi_cleanup(struct spi_device *spi)
{
        struct atmel_spi_device *asd = spi->controller_state;
        unsigned                gpio = (unsigned long) spi->controller_data;

        if (!asd)
                return;

        spi->controller_state = NULL;
        gpio_free(gpio);
        kfree(asd);
}

static inline unsigned int atmel_get_version(struct atmel_spi *as)
{
        return spi_readl(as, VERSION) & 0x00000fff;
}

static void atmel_get_caps(struct atmel_spi *as)
{
        unsigned int version;

        version = atmel_get_version(as);
        dev_info(&as->pdev->dev, "version: 0x%x\n", version);

        as->caps.is_spi2 = version > 0x121;
        as->caps.has_wdrbt = version >= 0x210;
        as->caps.has_dma_support = version >= 0x212;
}

/*-------------------------------------------------------------------------*/

static int atmel_spi_probe(struct platform_device *pdev)
{
        struct resource         *regs;
        int                     irq;
        struct clk              *clk;
        int                     ret;
        struct spi_master       *master;
        struct atmel_spi        *as;

        /* Select default pin state */
        pinctrl_pm_select_default_state(&pdev->dev);

        regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!regs)
                return -ENXIO;

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

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

        /* setup spi core then atmel-specific driver state */
        ret = -ENOMEM;
        master = spi_alloc_master(&pdev->dev, sizeof(*as));
        if (!master)
                goto out_free;

        /* the spi->mode bits understood by this driver: */
        master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
        master->bits_per_word_mask = SPI_BPW_RANGE_MASK(8, 16);
        master->dev.of_node = pdev->dev.of_node;
        master->bus_num = pdev->id;
        master->num_chipselect = master->dev.of_node ? 0 : 4;
        master->setup = atmel_spi_setup;
        master->transfer_one_message = atmel_spi_transfer_one_message;
        master->cleanup = atmel_spi_cleanup;
        master->auto_runtime_pm = true;
        platform_set_drvdata(pdev, master);

        as = spi_master_get_devdata(master);

        /*
         * Scratch buffer is used for throwaway rx and tx data.
         * It's coherent to minimize dcache pollution.
         */
        as->buffer = dma_alloc_coherent(&pdev->dev, BUFFER_SIZE,
                                        &as->buffer_dma, GFP_KERNEL);
        if (!as->buffer)
                goto out_free;

        spin_lock_init(&as->lock);

        as->pdev = pdev;
        as->regs = devm_ioremap_resource(&pdev->dev, regs);
        if (IS_ERR(as->regs)) {
                ret = PTR_ERR(as->regs);
                goto out_free_buffer;
        }
        as->phybase = regs->start;
        as->irq = irq;
        as->clk = clk;

        init_completion(&as->xfer_completion);

        atmel_get_caps(as);

        as->use_cs_gpios = true;
        if (atmel_spi_is_v2(as) &&
            !of_get_property(pdev->dev.of_node, "cs-gpios", NULL)) {
                as->use_cs_gpios = false;
                master->num_chipselect = 4;
        }

        as->use_dma = false;
        as->use_pdc = false;
        if (as->caps.has_dma_support) {
                ret = atmel_spi_configure_dma(as);
                if (ret == 0)
                        as->use_dma = true;
                else if (ret == -EPROBE_DEFER)
                        return ret;
        } else {
                as->use_pdc = true;
        }

        if (as->caps.has_dma_support && !as->use_dma)
                dev_info(&pdev->dev, "Atmel SPI Controller using PIO only\n");

        if (as->use_pdc) {
                ret = devm_request_irq(&pdev->dev, irq, atmel_spi_pdc_interrupt,
                                        0, dev_name(&pdev->dev), master);
        } else {
                ret = devm_request_irq(&pdev->dev, irq, atmel_spi_pio_interrupt,
                                        0, dev_name(&pdev->dev), master);
        }
        if (ret)
                goto out_unmap_regs;

        /* Initialize the hardware */
        ret = clk_prepare_enable(clk);
        if (ret)
                goto out_free_irq;
        spi_writel(as, CR, SPI_BIT(SWRST));
        spi_writel(as, CR, SPI_BIT(SWRST)); /* AT91SAM9263 Rev B workaround */
        if (as->caps.has_wdrbt) {
                spi_writel(as, MR, SPI_BIT(WDRBT) | SPI_BIT(MODFDIS)
                                | SPI_BIT(MSTR));
        } else {
                spi_writel(as, MR, SPI_BIT(MSTR) | SPI_BIT(MODFDIS));
        }

        if (as->use_pdc)
                spi_writel(as, PTCR, SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS));
        spi_writel(as, CR, SPI_BIT(SPIEN));

        as->fifo_size = 0;
        if (!of_property_read_u32(pdev->dev.of_node, "atmel,fifo-size",
                                  &as->fifo_size)) {
                dev_info(&pdev->dev, "Using FIFO (%u data)\n", as->fifo_size);
                spi_writel(as, CR, SPI_BIT(FIFOEN));
        }

        /* go! */
        dev_info(&pdev->dev, "Atmel SPI Controller at 0x%08lx (irq %d)\n",
                        (unsigned long)regs->start, irq);

        pm_runtime_set_autosuspend_delay(&pdev->dev, AUTOSUSPEND_TIMEOUT);
        pm_runtime_use_autosuspend(&pdev->dev);
        pm_runtime_set_active(&pdev->dev);
        pm_runtime_enable(&pdev->dev);

        ret = devm_spi_register_master(&pdev->dev, master);
        if (ret)
                goto out_free_dma;

        return 0;

out_free_dma:
        pm_runtime_disable(&pdev->dev);
        pm_runtime_set_suspended(&pdev->dev);

        if (as->use_dma)
                atmel_spi_release_dma(as);

        spi_writel(as, CR, SPI_BIT(SWRST));
        spi_writel(as, CR, SPI_BIT(SWRST)); /* AT91SAM9263 Rev B workaround */
        clk_disable_unprepare(clk);
out_free_irq:
out_unmap_regs:
out_free_buffer:
        dma_free_coherent(&pdev->dev, BUFFER_SIZE, as->buffer,
                        as->buffer_dma);
out_free:
        spi_master_put(master);
        return ret;
}

static int atmel_spi_remove(struct platform_device *pdev)
{
        struct spi_master       *master = platform_get_drvdata(pdev);
        struct atmel_spi        *as = spi_master_get_devdata(master);

        pm_runtime_get_sync(&pdev->dev);

        /* reset the hardware and block queue progress */
        spin_lock_irq(&as->lock);
        if (as->use_dma) {
                atmel_spi_stop_dma(as);
                atmel_spi_release_dma(as);
        }

        spi_writel(as, CR, SPI_BIT(SWRST));
        spi_writel(as, CR, SPI_BIT(SWRST)); /* AT91SAM9263 Rev B workaround */
        spi_readl(as, SR);
        spin_unlock_irq(&as->lock);

        dma_free_coherent(&pdev->dev, BUFFER_SIZE, as->buffer,
                        as->buffer_dma);

        clk_disable_unprepare(as->clk);

        pm_runtime_put_noidle(&pdev->dev);
        pm_runtime_disable(&pdev->dev);

        return 0;
}

#ifdef CONFIG_PM
static int atmel_spi_runtime_suspend(struct device *dev)
{
        struct spi_master *master = dev_get_drvdata(dev);
        struct atmel_spi *as = spi_master_get_devdata(master);

        clk_disable_unprepare(as->clk);
        pinctrl_pm_select_sleep_state(dev);

        return 0;
}

static int atmel_spi_runtime_resume(struct device *dev)
{
        struct spi_master *master = dev_get_drvdata(dev);
        struct atmel_spi *as = spi_master_get_devdata(master);

        pinctrl_pm_select_default_state(dev);

        return clk_prepare_enable(as->clk);
}

static int atmel_spi_suspend(struct device *dev)
{
        struct spi_master *master = dev_get_drvdata(dev);
        int ret;

        /* Stop the queue running */
        ret = spi_master_suspend(master);
        if (ret) {
                dev_warn(dev, "cannot suspend master\n");
                return ret;
        }

        if (!pm_runtime_suspended(dev))
                atmel_spi_runtime_suspend(dev);

        return 0;
}

static int atmel_spi_resume(struct device *dev)
{
        struct spi_master *master = dev_get_drvdata(dev);
        int ret;

        if (!pm_runtime_suspended(dev)) {
                ret = atmel_spi_runtime_resume(dev);
                if (ret)
                        return ret;
        }

        /* Start the queue running */
        ret = spi_master_resume(master);
        if (ret)
                dev_err(dev, "problem starting queue (%d)\n", ret);

        return ret;
}

static const struct dev_pm_ops atmel_spi_pm_ops = {
        SET_SYSTEM_SLEEP_PM_OPS(atmel_spi_suspend, atmel_spi_resume)
        SET_RUNTIME_PM_OPS(atmel_spi_runtime_suspend,
                           atmel_spi_runtime_resume, NULL)
};
#define ATMEL_SPI_PM_OPS        (&atmel_spi_pm_ops)
#else
#define ATMEL_SPI_PM_OPS        NULL
#endif

#if defined(CONFIG_OF)
static const struct of_device_id atmel_spi_dt_ids[] = {
        { .compatible = "atmel,at91rm9200-spi" },
        { /* sentinel */ }
};

MODULE_DEVICE_TABLE(of, atmel_spi_dt_ids);
#endif

static struct platform_driver atmel_spi_driver = {
        .driver         = {
                .name   = "atmel_spi",
                .pm     = ATMEL_SPI_PM_OPS,
                .of_match_table = of_match_ptr(atmel_spi_dt_ids),
        },
        .probe          = atmel_spi_probe,
        .remove         = atmel_spi_remove,
};
module_platform_driver(atmel_spi_driver);

MODULE_DESCRIPTION("Atmel AT32/AT91 SPI Controller driver");
MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:atmel_spi");