spi/spi-atmel: add dmaengine support

Add dmaengine support.

Using "has_dma_support" member of struct is used to select
the transfer mode: dmaengine or pdc.

For the dmaengine transfer mode, it supports both 8 bits and 16 bits transfer.

For the dmaengine transfer mode, if it fails to config dmaengine,
or if the message length is less than 16 bytes, it will use the PIO transfer mode.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
[wenyou.yang@atmel.com: using "has_dma_support" to select dmaengine as the spi xfer mode]
[wenyou.yang@atmel.com: fix DMA: OOPS if buffer > 4096 bytes]
[wenyou.yang@atmel.com: submit the patch]
Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
[richard.genoud@gmail.com: update with dmaengine interface]
[richard.genoud@gmail.com: fix __init/__devinit sections mismatch]
[richard.genoud@gmail.com: adapt to slave_config changes]
[richard.genoud@gmail.com: add support t0 16 bits transfer]
Tested-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 566 insertions, 21 deletions

diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index 3625951e5df5..787bd2c22bca 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -15,11 +15,13 @@
 #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>
@@ -182,6 +184,22 @@
 #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;
@@ -206,16 +224,23 @@ struct atmel_spi {
 
 	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 */
@@ -284,6 +309,7 @@ static void cs_activate(struct atmel_spi *as, struct spi_device *spi)
 					| SPI_BIT(MODFDIS)
 					| SPI_BIT(MSTR));
 		}
+
 		mr = spi_readl(as, MR);
 		gpio_set_value(asd->npcs_pin, active);
 	} else {
@@ -344,6 +370,12 @@ 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)
 {
@@ -355,6 +387,265 @@ 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)
+		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\n",
+		xfer, xfer->len, xfer->tx_buf, xfer->rx_buf);
+
+	/* 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,
@@ -372,6 +663,7 @@ static void atmel_spi_next_xfer_data(struct spi_master *master,
 		if (len > BUFFER_SIZE)
 			len = BUFFER_SIZE;
 	}
+
 	if (xfer->tx_buf)
 		*tx_dma = xfer->tx_dma + xfer->len - *plen;
 	else {
@@ -387,10 +679,10 @@ static void atmel_spi_next_xfer_data(struct spi_master *master,
 }
 
 /*
- * Submit next transfer for DMA.
+ * Submit next transfer for PDC.
  * lock is held, spi irq is blocked
  */
-static void atmel_spi_next_xfer(struct spi_master *master,
+static void atmel_spi_pdc_next_xfer(struct spi_master *master,
 				struct spi_message *msg)
 {
 	struct atmel_spi	*as = spi_master_get_devdata(master);
@@ -487,6 +779,48 @@ static void atmel_spi_next_xfer(struct spi_master *master,
 	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);
@@ -511,7 +845,10 @@ static void atmel_spi_next_message(struct spi_master *master)
 	} else
 		cs_activate(as, spi);
 
-	atmel_spi_next_xfer(master, msg);
+	if (as->use_pdc)
+		atmel_spi_pdc_next_xfer(master, msg);
+	else
+		atmel_spi_dma_next_xfer(master, msg);
 }
 
 /*
@@ -564,6 +901,11 @@ static void atmel_spi_dma_unmap_xfer(struct spi_master *master,
 				 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)
@@ -589,14 +931,183 @@ atmel_spi_msg_done(struct spi_master *master, struct atmel_spi *as,
 	as->done_status = 0;
 
 	/* continue if needed */
-	if (list_empty(&as->queue) || as->stopping)
-		spi_writel(as, PTCR, SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS));
-	else
+	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;
+	unsigned long	xfer_pos = xfer->len - as->current_remaining_bytes;
+
+	if (xfer->rx_buf) {
+		rxp = ((u8 *)xfer->rx_buf) + xfer_pos;
+		*rxp = spi_readl(as, RDR);
+	} else {
+		spi_readl(as, RDR);
+	}
+
+	as->current_remaining_bytes--;
+
+	if (as->current_remaining_bytes) {
+		if (xfer->tx_buf) {
+			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)
+{
+	struct spi_master	*master = (struct spi_master *)data;
+	struct atmel_spi	*as = spi_master_get_devdata(master);
+	struct spi_message	*msg;
+	struct spi_transfer	*xfer;
+
+	dev_vdbg(master->dev.parent, "atmel_spi_tasklet_func\n");
+
+	atmel_spi_lock(as);
+
+	xfer = as->current_transfer;
+
+	if (xfer == NULL)
+		/* already been there */
+		goto tasklet_out;
+
+	msg = list_entry(as->queue.next, struct spi_message, queue);
+
+	if (as->current_remaining_bytes == 0) {
+		if (as->done_status < 0) {
+			/* error happened (overrun) */
+			if (atmel_spi_use_dma(as, xfer))
+				atmel_spi_stop_dma(as);
+		} else {
+			/* only update length if no error */
+			msg->actual_length += xfer->len;
+		}
+
+		if (atmel_spi_use_dma(as, xfer))
+			if (!msg->is_dma_mapped)
+				atmel_spi_dma_unmap_xfer(master, xfer);
+
+		if (xfer->delay_usecs)
+			udelay(xfer->delay_usecs);
+
+		if (atmel_spi_xfer_is_last(msg, xfer) || as->done_status < 0) {
+			/* report completed (or erroneous) message */
+			atmel_spi_msg_done(master, as, msg, xfer->cs_change);
+		} else {
+			if (xfer->cs_change) {
+				cs_deactivate(as, msg->spi);
+				udelay(1);
+				cs_activate(as, msg->spi);
+			}
+
+			/*
+			 * Not done yet. Submit the next transfer.
+			 *
+			 * FIXME handle protocol options for xfer
+			 */
+			atmel_spi_dma_next_xfer(master, msg);
+		}
+	} else {
+		/*
+		 * Keep going, we still have data to send in
+		 * the current transfer.
+		 */
+		atmel_spi_dma_next_xfer(master, msg);
+	}
+
+tasklet_out:
+	atmel_spi_unlock(as);
+}
+
+/* Interrupt
+ *
+ * No need for locking in this Interrupt handler: done_status is the
+ * only information modified. What we need is the update of this field
+ * before tasklet runs. This is ensured by using barrier.
+ */
+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.
+		 *
+		 * All actions are done in tasklet with done_status indication
+		 */
+		as->done_status = -EIO;
+		smp_wmb();
+
+		/* Clear any overrun happening while cleaning up */
+		spi_readl(as, SR);
+
+		tasklet_schedule(&as->tasklet);
+
+	} else if (pending & SPI_BIT(RDRF)) {
+		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) {
+				/* no more data to xfer, kick tasklet */
+				spi_writel(as, IDR, pending);
+				tasklet_schedule(&as->tasklet);
+			}
+		}
+
+		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_interrupt(int irq, void *dev_id)
+atmel_spi_pdc_interrupt(int irq, void *dev_id)
 {
 	struct spi_master	*master = dev_id;
 	struct atmel_spi	*as = spi_master_get_devdata(master);
@@ -697,14 +1208,14 @@ atmel_spi_interrupt(int irq, void *dev_id)
 				 *
 				 * FIXME handle protocol options for xfer
 				 */
-				atmel_spi_next_xfer(master, msg);
+				atmel_spi_pdc_next_xfer(master, msg);
 			}
 		} else {
 			/*
 			 * Keep going, we still have data to send in
 			 * the current transfer.
 			 */
-			atmel_spi_next_xfer(master, msg);
+			atmel_spi_pdc_next_xfer(master, msg);
 		}
 	}
 
@@ -875,13 +1386,10 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
 
 		/*
 		 * DMA map early, for performance (empties dcache ASAP) and
-		 * better fault reporting.  This is a DMA-only driver.
-		 *
-		 * NOTE that if dma_unmap_single() ever starts to do work on
-		 * platforms supported by this driver, we would need to clean
-		 * up mappings for previously-mapped transfers.
+		 * better fault reporting.
 		 */
-		if (!msg->is_dma_mapped) {
+		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;
 		}
@@ -1000,6 +1508,7 @@ static int atmel_spi_probe(struct platform_device *pdev)
 
 	spin_lock_init(&as->lock);
 	INIT_LIST_HEAD(&as->queue);
+
 	as->pdev = pdev;
 	as->regs = ioremap(regs->start, resource_size(regs));
 	if (!as->regs)
@@ -1010,8 +1519,28 @@ static int atmel_spi_probe(struct platform_device *pdev)
 
 	atmel_get_caps(as);
 
-	ret = request_irq(irq, atmel_spi_interrupt, 0,
-			dev_name(&pdev->dev), master);
+	as->use_dma = false;
+	as->use_pdc = false;
+	if (as->caps.has_dma_support) {
+		if (atmel_spi_configure_dma(as) == 0)
+			as->use_dma = true;
+	} 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 = request_irq(irq, atmel_spi_pdc_interrupt, 0,
+					dev_name(&pdev->dev), master);
+	} else {
+		tasklet_init(&as->tasklet, atmel_spi_tasklet_func,
+					(unsigned long)master);
+
+		ret = request_irq(irq, atmel_spi_pio_interrupt, 0,
+					dev_name(&pdev->dev), master);
+	}
 	if (ret)
 		goto out_unmap_regs;
 
@@ -1025,7 +1554,9 @@ static int atmel_spi_probe(struct platform_device *pdev)
 	} else {
 		spi_writel(as, MR, SPI_BIT(MSTR) | SPI_BIT(MODFDIS));
 	}
-	spi_writel(as, PTCR, SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS));
+
+	if (as->use_pdc)
+		spi_writel(as, PTCR, SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS));
 	spi_writel(as, CR, SPI_BIT(SPIEN));
 
 	/* go! */
@@ -1034,11 +1565,14 @@ static int atmel_spi_probe(struct platform_device *pdev)
 
 	ret = spi_register_master(master);
 	if (ret)
-		goto out_reset_hw;
+		goto out_free_dma;
 
 	return 0;
 
-out_reset_hw:
+out_free_dma:
+	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(clk);
@@ -1046,6 +1580,8 @@ out_reset_hw:
 out_unmap_regs:
 	iounmap(as->regs);
 out_free_buffer:
+	if (!as->use_pdc)
+		tasklet_kill(&as->tasklet);
 	dma_free_coherent(&pdev->dev, BUFFER_SIZE, as->buffer,
 			as->buffer_dma);
 out_free:
@@ -1064,6 +1600,11 @@ static int atmel_spi_remove(struct platform_device *pdev)
 	/* reset the hardware and block queue progress */
 	spin_lock_irq(&as->lock);
 	as->stopping = 1;
+	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);
@@ -1072,13 +1613,17 @@ static int atmel_spi_remove(struct platform_device *pdev)
 	/* Terminate remaining queued transfers */
 	list_for_each_entry(msg, &as->queue, queue) {
 		list_for_each_entry(xfer, &msg->transfers, transfer_list) {
-			if (!msg->is_dma_mapped)
+			if (!msg->is_dma_mapped
+				&& (atmel_spi_use_dma(as, xfer)
+					|| as->use_pdc))
 				atmel_spi_dma_unmap_xfer(master, xfer);
 		}
 		msg->status = -ESHUTDOWN;
 		msg->complete(msg->context);
 	}
 
+	if (!as->use_pdc)
+		tasklet_kill(&as->tasklet);
 	dma_free_coherent(&pdev->dev, BUFFER_SIZE, as->buffer,
 			as->buffer_dma);