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/init.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/atmel.h>
#include <linux/platform_data/dma-atmel.h>
#include <linux/of.h>

#include <linux/io.h>
#include <linux/gpio.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_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

/* 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

/* 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

/* 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

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

/* use PIO for small transfers, avoiding DMA setup/teardown overhead and
 * cache operations; better heuristics consider wordsize and bitrate.
 */
#define DMA_MIN_BYTES	16

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_device	*stay;

	u8			stopping;
	struct list_head	queue;
	struct tasklet_struct	tasklet;
	struct spi_transfer	*current_transfer;
	unsigned long		current_remaining_bytes;
	struct spi_transfer	*next_transfer;
	unsigned long		next_remaining_bytes;
	int			done_status;

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

	struct atmel_spi_caps	caps;

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

/* 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);
		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 (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 (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)
{
	spin_lock_irqsave(&as->lock, as->flags);
}

static void atmel_spi_unlock(struct atmel_spi *as)
{
	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 inline int atmel_spi_xfer_is_last(struct spi_message *msg,
					struct spi_transfer *xfer)
{
	return msg->transfers.prev == &xfer->transfer_list;
}

static inline int atmel_spi_xfer_can_be_chained(struct spi_transfer *xfer)
{
	return xfer->delay_usecs == 0 && !xfer->cs_change;
}

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;

	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;
	}

	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 bool filter(struct dma_chan *chan, void *slave)
{
	struct	at_dma_slave *sl = slave;

	if (sl->dma_dev == chan->device->dev) {
		chan->private = sl;
		return true;
	} else {
		return false;
	}
}

static int atmel_spi_configure_dma(struct atmel_spi *as)
{
	struct at_dma_slave *sdata = &as->dma.dma_slave;
	struct dma_slave_config	slave_config;
	int err;

	if (sdata && sdata->dma_dev) {
		dma_cap_mask_t mask;

		/* Try to grab two DMA channels */
		dma_cap_zero(mask);
		dma_cap_set(DMA_SLAVE, mask);
		as->dma.chan_tx = dma_request_channel(mask, filter, sdata);
		if (as->dma.chan_tx)
			as->dma.chan_rx =
				dma_request_channel(mask, filter, sdata);
	}
	if (!as->dma.chan_rx || !as->dma.chan_tx) {
		dev_err(&as->pdev->dev,
			"DMA 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 (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)
		as->dma.chan_rx->device->device_control(as->dma.chan_rx,
							DMA_TERMINATE_ALL, 0);
	if (as->dma.chan_tx)
		as->dma.chan_tx->device->device_control(as->dma.chan_tx,
							DMA_TERMINATE_ALL, 0);
}

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);

	/* trigger SPI tasklet */
	tasklet_schedule(&as->tasklet);
}

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

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

	as->current_remaining_bytes = xfer->len;

	/* 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));
		else
			spi_writel(as, TDR, *(u8 *)(xfer->tx_buf));
	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));
}

/*
 * Submit next transfer for DMA.
 * lock is held, spi tasklet is blocked
 */
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 = rxchan->device->device_prep_slave_sg(rxchan,
					&as->dma.sgrx,
					1,
					DMA_FROM_DEVICE,
					DMA_PREP_INTERRUPT | DMA_CTRL_ACK,
					NULL);
	if (!rxdesc)
		goto err_dma;

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

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

/*
 * 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 atmel_spi	*as = spi_master_get_devdata(master);
	struct spi_transfer	*xfer;
	u32			len, remaining;
	u32			ieval;
	dma_addr_t		tx_dma, rx_dma;

	if (!as->current_transfer)
		xfer = list_entry(msg->transfers.next,
				struct spi_transfer, transfer_list);
	else if (!as->next_transfer)
		xfer = list_entry(as->current_transfer->transfer_list.next,
				struct spi_transfer, transfer_list);
	else
		xfer = NULL;

	if (xfer) {
		spi_writel(as, PTCR, SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS));

		len = xfer->len;
		atmel_spi_next_xfer_data(master, xfer, &tx_dma, &rx_dma, &len);
		remaining = xfer->len - 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/%08x rx %p/%08x\n",
			xfer, xfer->len, xfer->tx_buf, xfer->tx_dma,
			xfer->rx_buf, xfer->rx_dma);
	} else {
		xfer = as->next_transfer;
		remaining = as->next_remaining_bytes;
	}

	as->current_transfer = xfer;
	as->current_remaining_bytes = remaining;

	if (remaining > 0)
		len = remaining;
	else if (!atmel_spi_xfer_is_last(msg, xfer)
			&& atmel_spi_xfer_can_be_chained(xfer)) {
		xfer = list_entry(xfer->transfer_list.next,
				struct spi_transfer, transfer_list);
		len = xfer->len;
	} else
		xfer = NULL;

	as->next_transfer = xfer;

	if (xfer) {
		u32	total;

		total = len;
		atmel_spi_next_xfer_data(master, xfer, &tx_dma, &rx_dma, &len);
		as->next_remaining_bytes = total - 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/%08x rx %p/%08x\n",
			xfer, xfer->len, xfer->tx_buf, xfer->tx_dma,
			xfer->rx_buf, xfer->rx_dma);
		ieval = SPI_BIT(ENDRX) | SPI_BIT(OVRES);
	} else {
		spi_writel(as, RNCR, 0);
		spi_writel(as, TNCR, 0);
		ieval = SPI_BIT(RXBUFF) | SPI_BIT(ENDRX) | SPI_BIT(OVRES);
	}

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

/*
 * Choose way to submit next transfer and start it.
 * lock is held, spi tasklet is blocked
 */
static void atmel_spi_dma_next_xfer(struct spi_master *master,
				struct spi_message *msg)
{
	struct atmel_spi	*as = spi_master_get_devdata(master);
	struct spi_transfer	*xfer;
	u32	remaining, len;

	remaining = as->current_remaining_bytes;
	if (remaining) {
		xfer = as->current_transfer;
		len = remaining;
	} else {
		if (!as->current_transfer)
			xfer = list_entry(msg->transfers.next,
				struct spi_transfer, transfer_list);
		else
			xfer = list_entry(
				as->current_transfer->transfer_list.next,
					struct spi_transfer, transfer_list);

		as->current_transfer = xfer;
		len = xfer->len;
	}

	if (atmel_spi_use_dma(as, xfer)) {
		u32 total = len;
		if (!atmel_spi_next_xfer_dma_submit(master, xfer, &len)) {
			as->current_remaining_bytes = total - len;
			return;
		} else {
			dev_err(&msg->spi->dev, "unable to use DMA, fallback to PIO\n");
		}
	}

	/* use PIO if error appened using DMA */
	atmel_spi_next_xfer_pio(master, xfer);
}

static void atmel_spi_next_message(struct spi_master *master)
{
	struct atmel_spi	*as = spi_master_get_devdata(master);
	struct spi_message	*msg;
	struct spi_device	*spi;

	BUG_ON(as->current_transfer);

	msg = list_entry(as->queue.next, struct spi_message, queue);
	spi = msg->spi;

	dev_dbg(master->dev.parent, "start message %p for %s\n",
			msg, dev_name(&spi->dev));

	/* select chip if it's not still active */
	if (as->stay) {
		if (as->stay != spi) {
			cs_deactivate(as, as->stay);
			cs_activate(as, spi);
		}
		as->stay = NULL;
	} else
		cs_activate(as, spi);

	if (as->use_pdc)
		atmel_spi_pdc_next_xfer(master, msg);
	else
		atmel_spi_dma_next_xfer(master, msg);
}

/*
 * 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_msg_done(struct spi_master *master, struct atmel_spi *as,
		struct spi_message *msg, int stay)
{
	if (!stay || as->done_status < 0)
		cs_deactivate(as, msg->spi);
	else
		as->stay = msg->spi;

	list_del(&msg->queue);
	msg->status = as->done_status;

	dev_dbg(master->dev.parent,
		"xfer complete: %u bytes transferred\n",
		msg->actual_length);

	atmel_spi_unlock(as);
	msg->complete(msg->context);
	atmel_spi_lock(as);

	as->current_transfer = NULL;
	as->next_transfer = NULL;
	as->done_status = 0;

	/* continue if needed */
	if (list_empty(&as->queue) || as->stopping) {
		if (as->use_pdc)
			atmel_spi_disable_pdc_transfer(as);
	} else {
		atmel_spi_next_message(master);
	}
}

/* Called from IRQ
 * lock is held
 *
 * 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)
{
	u8		*txp;
	u8		*rxp;
	u16		*txp16;
	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) {
		as->current_remaining_bytes -= 2;
		if (as->current_remaining_bytes < 0)
			as->current_remaining_bytes = 0;
	} else {
		as->current_remaining_bytes--;
	}

	if (as->current_remaining_bytes) {
		if (xfer->tx_buf) {
			if (xfer->bits_per_word > 8) {
				txp16 = (u16 *)(((u8 *)xfer->tx_buf)
							+ xfer_pos + 2);
				spi_writel(as, TDR, *txp16);
			} else {
				txp = ((u8 *)xfer->tx_buf) + xfer_pos + 1;
				spi_writel(as, TDR, *txp);
			}
		} else {
			spi_writel(as, TDR, 0);
		}
	}
}

/* Tasklet
 * Called from DMA callback + pio transfer and overrun IRQ.
 */
static void atmel_spi_tasklet_func(unsigned long data)
{