1 files changed, 976 insertions, 0 deletions

diff --git a/drivers/spi/spi-ep93xx.c b/drivers/spi/spi-ep93xx.c
new file mode 100644
index 000000000..bb00be8d1
--- /dev/null
+++ b/drivers/spi/spi-ep93xx.c
@@ -0,0 +1,976 @@
+/*
+ * Driver for Cirrus Logic EP93xx SPI controller.
+ *
+ * Copyright (C) 2010-2011 Mika Westerberg
+ *
+ * Explicit FIFO handling code was inspired by amba-pl022 driver.
+ *
+ * Chip select support using other than built-in GPIOs by H. Hartley Sweeten.
+ *
+ * For more information about the SPI controller see documentation on Cirrus
+ * Logic web site:
+ *     http://www.cirrus.com/en/pubs/manual/EP93xx_Users_Guide_UM1.pdf
+ *
+ * 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/io.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/dmaengine.h>
+#include <linux/bitops.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/sched.h>
+#include <linux/scatterlist.h>
+#include <linux/spi/spi.h>
+
+#include <linux/platform_data/dma-ep93xx.h>
+#include <linux/platform_data/spi-ep93xx.h>
+
+#define SSPCR0			0x0000
+#define SSPCR0_MODE_SHIFT	6
+#define SSPCR0_SCR_SHIFT	8
+
+#define SSPCR1			0x0004
+#define SSPCR1_RIE		BIT(0)
+#define SSPCR1_TIE		BIT(1)
+#define SSPCR1_RORIE		BIT(2)
+#define SSPCR1_LBM		BIT(3)
+#define SSPCR1_SSE		BIT(4)
+#define SSPCR1_MS		BIT(5)
+#define SSPCR1_SOD		BIT(6)
+
+#define SSPDR			0x0008
+
+#define SSPSR			0x000c
+#define SSPSR_TFE		BIT(0)
+#define SSPSR_TNF		BIT(1)
+#define SSPSR_RNE		BIT(2)
+#define SSPSR_RFF		BIT(3)
+#define SSPSR_BSY		BIT(4)
+#define SSPCPSR			0x0010
+
+#define SSPIIR			0x0014
+#define SSPIIR_RIS		BIT(0)
+#define SSPIIR_TIS		BIT(1)
+#define SSPIIR_RORIS		BIT(2)
+#define SSPICR			SSPIIR
+
+/* timeout in milliseconds */
+#define SPI_TIMEOUT		5
+/* maximum depth of RX/TX FIFO */
+#define SPI_FIFO_SIZE		8
+
+/**
+ * struct ep93xx_spi - EP93xx SPI controller structure
+ * @pdev: pointer to platform device
+ * @clk: clock for the controller
+ * @regs_base: pointer to ioremap()'d registers
+ * @sspdr_phys: physical address of the SSPDR register
+ * @wait: wait here until given transfer is completed
+ * @current_msg: message that is currently processed (or %NULL if none)
+ * @tx: current byte in transfer to transmit
+ * @rx: current byte in transfer to receive
+ * @fifo_level: how full is FIFO (%0..%SPI_FIFO_SIZE - %1). Receiving one
+ *              frame decreases this level and sending one frame increases it.
+ * @dma_rx: RX DMA channel
+ * @dma_tx: TX DMA channel
+ * @dma_rx_data: RX parameters passed to the DMA engine
+ * @dma_tx_data: TX parameters passed to the DMA engine
+ * @rx_sgt: sg table for RX transfers
+ * @tx_sgt: sg table for TX transfers
+ * @zeropage: dummy page used as RX buffer when only TX buffer is passed in by
+ *            the client
+ */
+struct ep93xx_spi {
+	const struct platform_device	*pdev;
+	struct clk			*clk;
+	void __iomem			*regs_base;
+	unsigned long			sspdr_phys;
+	struct completion		wait;
+	struct spi_message		*current_msg;
+	size_t				tx;
+	size_t				rx;
+	size_t				fifo_level;
+	struct dma_chan			*dma_rx;
+	struct dma_chan			*dma_tx;
+	struct ep93xx_dma_data		dma_rx_data;
+	struct ep93xx_dma_data		dma_tx_data;
+	struct sg_table			rx_sgt;
+	struct sg_table			tx_sgt;
+	void				*zeropage;
+};
+
+/**
+ * struct ep93xx_spi_chip - SPI device hardware settings
+ * @spi: back pointer to the SPI device
+ * @ops: private chip operations
+ */
+struct ep93xx_spi_chip {
+	const struct spi_device		*spi;
+	struct ep93xx_spi_chip_ops	*ops;
+};
+
+/* converts bits per word to CR0.DSS value */
+#define bits_per_word_to_dss(bpw)	((bpw) - 1)
+
+static void ep93xx_spi_write_u8(const struct ep93xx_spi *espi,
+				u16 reg, u8 value)
+{
+	writeb(value, espi->regs_base + reg);
+}
+
+static u8 ep93xx_spi_read_u8(const struct ep93xx_spi *spi, u16 reg)
+{
+	return readb(spi->regs_base + reg);
+}
+
+static void ep93xx_spi_write_u16(const struct ep93xx_spi *espi,
+				 u16 reg, u16 value)
+{
+	writew(value, espi->regs_base + reg);
+}
+
+static u16 ep93xx_spi_read_u16(const struct ep93xx_spi *spi, u16 reg)
+{
+	return readw(spi->regs_base + reg);
+}
+
+static int ep93xx_spi_enable(const struct ep93xx_spi *espi)
+{
+	u8 regval;
+	int err;
+
+	err = clk_enable(espi->clk);
+	if (err)
+		return err;
+
+	regval = ep93xx_spi_read_u8(espi, SSPCR1);
+	regval |= SSPCR1_SSE;
+	ep93xx_spi_write_u8(espi, SSPCR1, regval);
+
+	return 0;
+}
+
+static void ep93xx_spi_disable(const struct ep93xx_spi *espi)
+{
+	u8 regval;
+
+	regval = ep93xx_spi_read_u8(espi, SSPCR1);
+	regval &= ~SSPCR1_SSE;
+	ep93xx_spi_write_u8(espi, SSPCR1, regval);
+
+	clk_disable(espi->clk);
+}
+
+static void ep93xx_spi_enable_interrupts(const struct ep93xx_spi *espi)
+{
+	u8 regval;
+
+	regval = ep93xx_spi_read_u8(espi, SSPCR1);
+	regval |= (SSPCR1_RORIE | SSPCR1_TIE | SSPCR1_RIE);
+	ep93xx_spi_write_u8(espi, SSPCR1, regval);
+}
+
+static void ep93xx_spi_disable_interrupts(const struct ep93xx_spi *espi)
+{
+	u8 regval;
+
+	regval = ep93xx_spi_read_u8(espi, SSPCR1);
+	regval &= ~(SSPCR1_RORIE | SSPCR1_TIE | SSPCR1_RIE);
+	ep93xx_spi_write_u8(espi, SSPCR1, regval);
+}
+
+/**
+ * ep93xx_spi_calc_divisors() - calculates SPI clock divisors
+ * @espi: ep93xx SPI controller struct
+ * @rate: desired SPI output clock rate
+ * @div_cpsr: pointer to return the cpsr (pre-scaler) divider
+ * @div_scr: pointer to return the scr divider
+ */
+static int ep93xx_spi_calc_divisors(const struct ep93xx_spi *espi,
+				    u32 rate, u8 *div_cpsr, u8 *div_scr)
+{
+	struct spi_master *master = platform_get_drvdata(espi->pdev);
+	unsigned long spi_clk_rate = clk_get_rate(espi->clk);
+	int cpsr, scr;
+
+	/*
+	 * Make sure that max value is between values supported by the
+	 * controller. Note that minimum value is already checked in
+	 * ep93xx_spi_transfer_one_message().
+	 */
+	rate = clamp(rate, master->min_speed_hz, master->max_speed_hz);
+
+	/*
+	 * Calculate divisors so that we can get speed according the
+	 * following formula:
+	 *	rate = spi_clock_rate / (cpsr * (1 + scr))
+	 *
+	 * cpsr must be even number and starts from 2, scr can be any number
+	 * between 0 and 255.
+	 */
+	for (cpsr = 2; cpsr <= 254; cpsr += 2) {
+		for (scr = 0; scr <= 255; scr++) {
+			if ((spi_clk_rate / (cpsr * (scr + 1))) <= rate) {
+				*div_scr = (u8)scr;
+				*div_cpsr = (u8)cpsr;
+				return 0;
+			}
+		}
+	}
+
+	return -EINVAL;
+}
+
+static void ep93xx_spi_cs_control(struct spi_device *spi, bool control)
+{
+	struct ep93xx_spi_chip *chip = spi_get_ctldata(spi);
+	int value = (spi->mode & SPI_CS_HIGH) ? control : !control;
+
+	if (chip->ops && chip->ops->cs_control)
+		chip->ops->cs_control(spi, value);
+}
+
+/**
+ * ep93xx_spi_setup() - setup an SPI device
+ * @spi: SPI device to setup
+ *
+ * This function sets up SPI device mode, speed etc. Can be called multiple
+ * times for a single device. Returns %0 in case of success, negative error in
+ * case of failure. When this function returns success, the device is
+ * deselected.
+ */
+static int ep93xx_spi_setup(struct spi_device *spi)
+{
+	struct ep93xx_spi *espi = spi_master_get_devdata(spi->master);
+	struct ep93xx_spi_chip *chip;
+
+	chip = spi_get_ctldata(spi);
+	if (!chip) {
+		dev_dbg(&espi->pdev->dev, "initial setup for %s\n",
+			spi->modalias);
+
+		chip = kzalloc(sizeof(*chip), GFP_KERNEL);
+		if (!chip)
+			return -ENOMEM;
+
+		chip->spi = spi;
+		chip->ops = spi->controller_data;
+
+		if (chip->ops && chip->ops->setup) {
+			int ret = chip->ops->setup(spi);
+
+			if (ret) {
+				kfree(chip);
+				return ret;
+			}
+		}
+
+		spi_set_ctldata(spi, chip);
+	}
+
+	ep93xx_spi_cs_control(spi, false);
+	return 0;
+}
+
+/**
+ * ep93xx_spi_cleanup() - cleans up master controller specific state
+ * @spi: SPI device to cleanup
+ *
+ * This function releases master controller specific state for given @spi
+ * device.
+ */
+static void ep93xx_spi_cleanup(struct spi_device *spi)
+{
+	struct ep93xx_spi_chip *chip;
+
+	chip = spi_get_ctldata(spi);
+	if (chip) {
+		if (chip->ops && chip->ops->cleanup)
+			chip->ops->cleanup(spi);
+		spi_set_ctldata(spi, NULL);
+		kfree(chip);
+	}
+}
+
+/**
+ * ep93xx_spi_chip_setup() - configures hardware according to given @chip
+ * @espi: ep93xx SPI controller struct
+ * @chip: chip specific settings
+ * @speed_hz: transfer speed
+ * @bits_per_word: transfer bits_per_word
+ */
+static int ep93xx_spi_chip_setup(const struct ep93xx_spi *espi,
+				 const struct ep93xx_spi_chip *chip,
+				 u32 speed_hz, u8 bits_per_word)
+{
+	u8 dss = bits_per_word_to_dss(bits_per_word);
+	u8 div_cpsr = 0;
+	u8 div_scr = 0;
+	u16 cr0;
+	int err;
+
+	err = ep93xx_spi_calc_divisors(espi, speed_hz, &div_cpsr, &div_scr);
+	if (err)
+		return err;
+
+	cr0 = div_scr << SSPCR0_SCR_SHIFT;
+	cr0 |= (chip->spi->mode & (SPI_CPHA|SPI_CPOL)) << SSPCR0_MODE_SHIFT;
+	cr0 |= dss;
+
+	dev_dbg(&espi->pdev->dev, "setup: mode %d, cpsr %d, scr %d, dss %d\n",
+		chip->spi->mode, div_cpsr, div_scr, dss);
+	dev_dbg(&espi->pdev->dev, "setup: cr0 %#x\n", cr0);
+
+	ep93xx_spi_write_u8(espi, SSPCPSR, div_cpsr);
+	ep93xx_spi_write_u16(espi, SSPCR0, cr0);
+
+	return 0;
+}
+
+static void ep93xx_do_write(struct ep93xx_spi *espi, struct spi_transfer *t)
+{
+	if (t->bits_per_word > 8) {
+		u16 tx_val = 0;
+
+		if (t->tx_buf)
+			tx_val = ((u16 *)t->tx_buf)[espi->tx];
+		ep93xx_spi_write_u16(espi, SSPDR, tx_val);
+		espi->tx += sizeof(tx_val);
+	} else {
+		u8 tx_val = 0;
+
+		if (t->tx_buf)
+			tx_val = ((u8 *)t->tx_buf)[espi->tx];
+		ep93xx_spi_write_u8(espi, SSPDR, tx_val);
+		espi->tx += sizeof(tx_val);
+	}
+}
+
+static void ep93xx_do_read(struct ep93xx_spi *espi, struct spi_transfer *t)
+{
+	if (t->bits_per_word > 8) {
+		u16 rx_val;
+
+		rx_val = ep93xx_spi_read_u16(espi, SSPDR);
+		if (t->rx_buf)
+			((u16 *)t->rx_buf)[espi->rx] = rx_val;
+		espi->rx += sizeof(rx_val);
+	} else {
+		u8 rx_val;
+
+		rx_val = ep93xx_spi_read_u8(espi, SSPDR);
+		if (t->rx_buf)
+			((u8 *)t->rx_buf)[espi->rx] = rx_val;
+		espi->rx += sizeof(rx_val);
+	}
+}
+
+/**
+ * ep93xx_spi_read_write() - perform next RX/TX transfer
+ * @espi: ep93xx SPI controller struct
+ *
+ * This function transfers next bytes (or half-words) to/from RX/TX FIFOs. If
+ * called several times, the whole transfer will be completed. Returns
+ * %-EINPROGRESS when current transfer was not yet completed otherwise %0.
+ *
+ * When this function is finished, RX FIFO should be empty and TX FIFO should be
+ * full.
+ */
+static int ep93xx_spi_read_write(struct ep93xx_spi *espi)
+{
+	struct spi_message *msg = espi->current_msg;
+	struct spi_transfer *t = msg->state;
+
+	/* read as long as RX FIFO has frames in it */
+	while ((ep93xx_spi_read_u8(espi, SSPSR) & SSPSR_RNE)) {
+		ep93xx_do_read(espi, t);
+		espi->fifo_level--;
+	}
+
+	/* write as long as TX FIFO has room */
+	while (espi->fifo_level < SPI_FIFO_SIZE && espi->tx < t->len) {
+		ep93xx_do_write(espi, t);
+		espi->fifo_level++;
+	}
+
+	if (espi->rx == t->len)
+		return 0;
+
+	return -EINPROGRESS;
+}
+
+static void ep93xx_spi_pio_transfer(struct ep93xx_spi *espi)
+{
+	/*
+	 * Now everything is set up for the current transfer. We prime the TX
+	 * FIFO, enable interrupts, and wait for the transfer to complete.
+	 */
+	if (ep93xx_spi_read_write(espi)) {
+		ep93xx_spi_enable_interrupts(espi);
+		wait_for_completion(&espi->wait);
+	}
+}
+
+/**
+ * ep93xx_spi_dma_prepare() - prepares a DMA transfer
+ * @espi: ep93xx SPI controller struct
+ * @dir: DMA transfer direction
+ *
+ * Function configures the DMA, maps the buffer and prepares the DMA
+ * descriptor. Returns a valid DMA descriptor in case of success and ERR_PTR
+ * in case of failure.
+ */
+static struct dma_async_tx_descriptor *
+ep93xx_spi_dma_prepare(struct ep93xx_spi *espi, enum dma_transfer_direction dir)
+{
+	struct spi_transfer *t = espi->current_msg->state;
+	struct dma_async_tx_descriptor *txd;
+	enum dma_slave_buswidth buswidth;
+	struct dma_slave_config conf;
+	struct scatterlist *sg;
+	struct sg_table *sgt;
+	struct dma_chan *chan;
+	const void *buf, *pbuf;
+	size_t len = t->len;
+	int i, ret, nents;
+
+	if (t->bits_per_word > 8)
+		buswidth = DMA_SLAVE_BUSWIDTH_2_BYTES;
+	else
+		buswidth = DMA_SLAVE_BUSWIDTH_1_BYTE;
+
+	memset(&conf, 0, sizeof(conf));
+	conf.direction = dir;
+
+	if (dir == DMA_DEV_TO_MEM) {
+		chan = espi->dma_rx;
+		buf = t->rx_buf;
+		sgt = &espi->rx_sgt;
+
+		conf.src_addr = espi->sspdr_phys;
+		conf.src_addr_width = buswidth;
+	} else {
+		chan = espi->dma_tx;
+		buf = t->tx_buf;
+		sgt = &espi->tx_sgt;
+
+		conf.dst_addr = espi->sspdr_phys;
+		conf.dst_addr_width = buswidth;
+	}
+
+	ret = dmaengine_slave_config(chan, &conf);
+	if (ret)
+		return ERR_PTR(ret);
+
+	/*
+	 * We need to split the transfer into PAGE_SIZE'd chunks. This is
+	 * because we are using @espi->zeropage to provide a zero RX buffer
+	 * for the TX transfers and we have only allocated one page for that.
+	 *
+	 * For performance reasons we allocate a new sg_table only when
+	 * needed. Otherwise we will re-use the current one. Eventually the
+	 * last sg_table is released in ep93xx_spi_release_dma().
+	 */
+
+	nents = DIV_ROUND_UP(len, PAGE_SIZE);
+	if (nents != sgt->nents) {
+		sg_free_table(sgt);
+
+		ret = sg_alloc_table(sgt, nents, GFP_KERNEL);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+
+	pbuf = buf;
+	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
+		size_t bytes = min_t(size_t, len, PAGE_SIZE);
+
+		if (buf) {
+			sg_set_page(sg, virt_to_page(pbuf), bytes,
+				    offset_in_page(pbuf));
+		} else {
+			sg_set_page(sg, virt_to_page(espi->zeropage),
+				    bytes, 0);
+		}
+
+		pbuf += bytes;
+		len -= bytes;
+	}
+
+	if (WARN_ON(len)) {
+		dev_warn(&espi->pdev->dev, "len = %zu expected 0!\n", len);
+		return ERR_PTR(-EINVAL);
+	}
+
+	nents = dma_map_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
+	if (!nents)
+		return ERR_PTR(-ENOMEM);
+
+	txd = dmaengine_prep_slave_sg(chan, sgt->sgl, nents, dir, DMA_CTRL_ACK);
+	if (!txd) {
+		dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
+		return ERR_PTR(-ENOMEM);
+	}
+	return txd;
+}
+
+/**
+ * ep93xx_spi_dma_finish() - finishes with a DMA transfer
+ * @espi: ep93xx SPI controller struct
+ * @dir: DMA transfer direction
+ *
+ * Function finishes with the DMA transfer. After this, the DMA buffer is
+ * unmapped.
+ */
+static void ep93xx_spi_dma_finish(struct ep93xx_spi *espi,
+				  enum dma_transfer_direction dir)
+{
+	struct dma_chan *chan;
+	struct sg_table *sgt;
+
+	if (dir == DMA_DEV_TO_MEM) {
+		chan = espi->dma_rx;
+		sgt = &espi->rx_sgt;
+	} else {
+		chan = espi->dma_tx;
+		sgt = &espi->tx_sgt;
+	}
+
+	dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
+}
+
+static void ep93xx_spi_dma_callback(void *callback_param)
+{
+	complete(callback_param);
+}
+
+static void ep93xx_spi_dma_transfer(struct ep93xx_spi *espi)
+{
+	struct spi_message *msg = espi->current_msg;
+	struct dma_async_tx_descriptor *rxd, *txd;
+
+	rxd = ep93xx_spi_dma_prepare(espi, DMA_DEV_TO_MEM);
+	if (IS_ERR(rxd)) {
+		dev_err(&espi->pdev->dev, "DMA RX failed: %ld\n", PTR_ERR(rxd));
+		msg->status = PTR_ERR(rxd);
+		return;
+	}
+
+	txd = ep93xx_spi_dma_prepare(espi, DMA_MEM_TO_DEV);
+	if (IS_ERR(txd)) {
+		ep93xx_spi_dma_finish(espi, DMA_DEV_TO_MEM);
+		dev_err(&espi->pdev->dev, "DMA TX failed: %ld\n", PTR_ERR(rxd));
+		msg->status = PTR_ERR(txd);
+		return;
+	}
+
+	/* We are ready when RX is done */
+	rxd->callback = ep93xx_spi_dma_callback;
+	rxd->callback_param = &espi->wait;
+
+	/* Now submit both descriptors and wait while they finish */
+	dmaengine_submit(rxd);
+	dmaengine_submit(txd);
+
+	dma_async_issue_pending(espi->dma_rx);
+	dma_async_issue_pending(espi->dma_tx);
+
+	wait_for_completion(&espi->wait);
+
+	ep93xx_spi_dma_finish(espi, DMA_MEM_TO_DEV);
+	ep93xx_spi_dma_finish(espi, DMA_DEV_TO_MEM);
+}
+
+/**
+ * ep93xx_spi_process_transfer() - processes one SPI transfer
+ * @espi: ep93xx SPI controller struct
+ * @msg: current message
+ * @t: transfer to process
+ *
+ * This function processes one SPI transfer given in @t. Function waits until
+ * transfer is complete (may sleep) and updates @msg->status based on whether
+ * transfer was successfully processed or not.
+ */
+static void ep93xx_spi_process_transfer(struct ep93xx_spi *espi,
+					struct spi_message *msg,
+					struct spi_transfer *t)
+{
+	struct ep93xx_spi_chip *chip = spi_get_ctldata(msg->spi);
+	int err;
+
+	msg->state = t;
+
+	err = ep93xx_spi_chip_setup(espi, chip, t->speed_hz, t->bits_per_word);
+	if (err) {
+		dev_err(&espi->pdev->dev,
+			"failed to setup chip for transfer\n");
+		msg->status = err;
+		return;
+	}
+
+	espi->rx = 0;
+	espi->tx = 0;
+
+	/*
+	 * There is no point of setting up DMA for the transfers which will
+	 * fit into the FIFO and can be transferred with a single interrupt.
+	 * So in these cases we will be using PIO and don't bother for DMA.
+	 */
+	if (espi->dma_rx && t->len > SPI_FIFO_SIZE)
+		ep93xx_spi_dma_transfer(espi);
+	else
+		ep93xx_spi_pio_transfer(espi);
+
+	/*
+	 * In case of error during transmit, we bail out from processing
+	 * the message.
+	 */
+	if (msg->status)
+		return;
+
+	msg->actual_length += t->len;
+
+	/*
+	 * After this transfer is finished, perform any possible
+	 * post-transfer actions requested by the protocol driver.
+	 */
+	if (t->delay_usecs) {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		schedule_timeout(usecs_to_jiffies(t->delay_usecs));
+	}
+	if (t->cs_change) {
+		if (!list_is_last(&t->transfer_list, &msg->transfers)) {
+			/*
+			 * In case protocol driver is asking us to drop the
+			 * chipselect briefly, we let the scheduler to handle
+			 * any "delay" here.
+			 */
+			ep93xx_spi_cs_control(msg->spi, false);
+			cond_resched();
+			ep93xx_spi_cs_control(msg->spi, true);
+		}
+	}
+}
+
+/*
+ * ep93xx_spi_process_message() - process one SPI message
+ * @espi: ep93xx SPI controller struct
+ * @msg: message to process
+ *
+ * This function processes a single SPI message. We go through all transfers in
+ * the message and pass them to ep93xx_spi_process_transfer(). Chipselect is
+ * asserted during the whole message (unless per transfer cs_change is set).
+ *
+ * @msg->status contains %0 in case of success or negative error code in case of
+ * failure.
+ */
+static void ep93xx_spi_process_message(struct ep93xx_spi *espi,
+				       struct spi_message *msg)
+{
+	unsigned long timeout;
+	struct spi_transfer *t;
+	int err;
+
+	/*
+	 * Enable the SPI controller and its clock.
+	 */
+	err = ep93xx_spi_enable(espi);
+	if (err) {
+		dev_err(&espi->pdev->dev, "failed to enable SPI controller\n");
+		msg->status = err;
+		return;
+	}
+
+	/*
+	 * Just to be sure: flush any data from RX FIFO.
+	 */
+	timeout = jiffies + msecs_to_jiffies(SPI_TIMEOUT);
+	while (ep93xx_spi_read_u16(espi, SSPSR) & SSPSR_RNE) {
+		if (time_after(jiffies, timeout)) {
+			dev_warn(&espi->pdev->dev,
+				 "timeout while flushing RX FIFO\n");
+			msg->status = -ETIMEDOUT;
+			return;
+		}
+		ep93xx_spi_read_u16(espi, SSPDR);
+	}
+
+	/*
+	 * We explicitly handle FIFO level. This way we don't have to check TX
+	 * FIFO status using %SSPSR_TNF bit which may cause RX FIFO overruns.
+	 */
+	espi->fifo_level = 0;
+
+	/*
+	 * Assert the chipselect.
+	 */
+	ep93xx_spi_cs_control(msg->spi, true);
+
+	list_for_each_entry(t, &msg->transfers, transfer_list) {
+		ep93xx_spi_process_transfer(espi, msg, t);
+		if (msg->status)
+			break;
+	}
+
+	/*
+	 * Now the whole message is transferred (or failed for some reason). We
+	 * deselect the device and disable the SPI controller.
+	 */
+	ep93xx_spi_cs_control(msg->spi, false);
+	ep93xx_spi_disable(espi);
+}
+
+static int ep93xx_spi_transfer_one_message(struct spi_master *master,
+					   struct spi_message *msg)
+{
+	struct ep93xx_spi *espi = spi_master_get_devdata(master);
+
+	msg->state = NULL;
+	msg->status = 0;
+	msg->actual_length = 0;
+
+	espi->current_msg = msg;
+	ep93xx_spi_process_message(espi, msg);
+	espi->current_msg = NULL;
+
+	spi_finalize_current_message(master);
+
+	return 0;
+}
+
+static irqreturn_t ep93xx_spi_interrupt(int irq, void *dev_id)
+{
+	struct ep93xx_spi *espi = dev_id;
+	u8 irq_status = ep93xx_spi_read_u8(espi, SSPIIR);
+
+	/*
+	 * If we got ROR (receive overrun) interrupt we know that something is
+	 * wrong. Just abort the message.
+	 */
+	if (unlikely(irq_status & SSPIIR_RORIS)) {
+		/* clear the overrun interrupt */
+		ep93xx_spi_write_u8(espi, SSPICR, 0);
+		dev_warn(&espi->pdev->dev,
+			 "receive overrun, aborting the message\n");
+		espi->current_msg->status = -EIO;
+	} else {
+		/*
+		 * Interrupt is either RX (RIS) or TX (TIS). For both cases we
+		 * simply execute next data transfer.
+		 */
+		if (ep93xx_spi_read_write(espi)) {
+			/*
+			 * In normal case, there still is some processing left
+			 * for current transfer. Let's wait for the next
+			 * interrupt then.
+			 */
+			return IRQ_HANDLED;
+		}
+	}
+
+	/*
+	 * Current transfer is finished, either with error or with success. In
+	 * any case we disable interrupts and notify the worker to handle
+	 * any post-processing of the message.
+	 */
+	ep93xx_spi_disable_interrupts(espi);
+	complete(&espi->wait);
+	return IRQ_HANDLED;
+}
+
+static bool ep93xx_spi_dma_filter(struct dma_chan *chan, void *filter_param)
+{
+	if (ep93xx_dma_chan_is_m2p(chan))
+		return false;
+
+	chan->private = filter_param;
+	return true;
+}
+
+static int ep93xx_spi_setup_dma(struct ep93xx_spi *espi)
+{
+	dma_cap_mask_t mask;
+	int ret;
+
+	espi->zeropage = (void *)get_zeroed_page(GFP_KERNEL);
+	if (!espi->zeropage)
+		return -ENOMEM;
+
+	dma_cap_zero(mask);
+	dma_cap_set(DMA_SLAVE, mask);
+
+	espi->dma_rx_data.port = EP93XX_DMA_SSP;
+	espi->dma_rx_data.direction = DMA_DEV_TO_MEM;
+	espi->dma_rx_data.name = "ep93xx-spi-rx";
+
+	espi->dma_rx = dma_request_channel(mask, ep93xx_spi_dma_filter,
+					   &espi->dma_rx_data);
+	if (!espi->dma_rx) {
+		ret = -ENODEV;
+		goto fail_free_page;
+	}
+
+	espi->dma_tx_data.port = EP93XX_DMA_SSP;
+	espi->dma_tx_data.direction = DMA_MEM_TO_DEV;
+	espi->dma_tx_data.name = "ep93xx-spi-tx";
+
+	espi->dma_tx = dma_request_channel(mask, ep93xx_spi_dma_filter,
+					   &espi->dma_tx_data);
+	if (!espi->dma_tx) {
+		ret = -ENODEV;
+		goto fail_release_rx;
+	}
+
+	return 0;
+
+fail_release_rx:
+	dma_release_channel(espi->dma_rx);
+	espi->dma_rx = NULL;
+fail_free_page:
+	free_page((unsigned long)espi->zeropage);
+
+	return ret;
+}
+
+static void ep93xx_spi_release_dma(struct ep93xx_spi *espi)
+{
+	if (espi->dma_rx) {
+		dma_release_channel(espi->dma_rx);
+		sg_free_table(&espi->rx_sgt);
+	}
+	if (espi->dma_tx) {
+		dma_release_channel(espi->dma_tx);
+		sg_free_table(&espi->tx_sgt);
+	}
+
+	if (espi->zeropage)
+		free_page((unsigned long)espi->zeropage);
+}
+
+static int ep93xx_spi_probe(struct platform_device *pdev)
+{
+	struct spi_master *master;
+	struct ep93xx_spi_info *info;
+	struct ep93xx_spi *espi;
+	struct resource *res;
+	int irq;
+	int error;
+
+	info = dev_get_platdata(&pdev->dev);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "failed to get irq resources\n");
+		return -EBUSY;
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "unable to get iomem resource\n");
+		return -ENODEV;
+	}
+
+	master = spi_alloc_master(&pdev->dev, sizeof(*espi));
+	if (!master)
+		return -ENOMEM;
+
+	master->setup = ep93xx_spi_setup;
+	master->transfer_one_message = ep93xx_spi_transfer_one_message;
+	master->cleanup = ep93xx_spi_cleanup;
+	master->bus_num = pdev->id;
+	master->num_chipselect = info->num_chipselect;
+	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
+	master->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 16);
+
+	platform_set_drvdata(pdev, master);
+
+	espi = spi_master_get_devdata(master);
+
+	espi->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(espi->clk)) {
+		dev_err(&pdev->dev, "unable to get spi clock\n");
+		error = PTR_ERR(espi->clk);
+		goto fail_release_master;
+	}
+
+	init_completion(&espi->wait);
+
+	/*
+	 * Calculate maximum and minimum supported clock rates
+	 * for the controller.
+	 */
+	master->max_speed_hz = clk_get_rate(espi->clk) / 2;
+	master->min_speed_hz = clk_get_rate(espi->clk) / (254 * 256);
+	espi->pdev = pdev;
+
+	espi->sspdr_phys = res->start + SSPDR;
+
+	espi->regs_base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(espi->regs_base)) {
+		error = PTR_ERR(espi->regs_base);
+		goto fail_release_master;
+	}
+
+	error = devm_request_irq(&pdev->dev, irq, ep93xx_spi_interrupt,
+				0, "ep93xx-spi", espi);
+	if (error) {
+		dev_err(&pdev->dev, "failed to request irq\n");
+		goto fail_release_master;
+	}
+
+	if (info->use_dma && ep93xx_spi_setup_dma(espi))
+		dev_warn(&pdev->dev, "DMA setup failed. Falling back to PIO\n");
+
+	/* make sure that the hardware is disabled */
+	ep93xx_spi_write_u8(espi, SSPCR1, 0);
+
+	error = devm_spi_register_master(&pdev->dev, master);
+	if (error) {
+		dev_err(&pdev->dev, "failed to register SPI master\n");
+		goto fail_free_dma;
+	}
+
+	dev_info(&pdev->dev, "EP93xx SPI Controller at 0x%08lx irq %d\n",
+		 (unsigned long)res->start, irq);
+
+	return 0;
+
+fail_free_dma:
+	ep93xx_spi_release_dma(espi);
+fail_release_master:
+	spi_master_put(master);
+
+	return error;
+}
+
+static int ep93xx_spi_remove(struct platform_device *pdev)
+{
+	struct spi_master *master = platform_get_drvdata(pdev);
+	struct ep93xx_spi *espi = spi_master_get_devdata(master);
+
+	ep93xx_spi_release_dma(espi);
+
+	return 0;
+}
+
+static struct platform_driver ep93xx_spi_driver = {
+	.driver		= {
+		.name	= "ep93xx-spi",
+	},
+	.probe		= ep93xx_spi_probe,
+	.remove		= ep93xx_spi_remove,
+};
+module_platform_driver(ep93xx_spi_driver);
+
+MODULE_DESCRIPTION("EP93xx SPI Controller driver");
+MODULE_AUTHOR("Mika Westerberg <mika.westerberg@iki.fi>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ep93xx-spi");