[ALSA] Add ASoC drivers for the Freescale MPC8610 SoC

Add the ASoC drivers for the Freescale MPC8610 SoC and the MPC8610 HPCD
reference board.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

1 files changed, 839 insertions, 0 deletions

diff --git a/sound/soc/fsl/fsl_dma.c b/sound/soc/fsl/fsl_dma.c
new file mode 100644
index 00000000000..2173203b29a
--- /dev/null
+++ b/sound/soc/fsl/fsl_dma.c
@@ -0,0 +1,839 @@
+/*
+ * Freescale DMA ALSA SoC PCM driver
+ *
+ * Author: Timur Tabi <timur@freescale.com>
+ *
+ * Copyright 2007-2008 Freescale Semiconductor, Inc.  This file is licensed
+ * under the terms of the GNU General Public License version 2.  This
+ * program is licensed "as is" without any warranty of any kind, whether
+ * express or implied.
+ *
+ * This driver implements ASoC support for the Elo DMA controller, which is
+ * the DMA controller on Freescale 83xx, 85xx, and 86xx SOCs. In ALSA terms,
+ * the PCM driver is what handles the DMA buffer.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/dma-mapping.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+
+#include <sound/driver.h>
+#include <sound/core.h>
+#include <sound/pcm.h>
+#include <sound/pcm_params.h>
+#include <sound/soc.h>
+
+#include <asm/io.h>
+
+#include "fsl_dma.h"
+
+/*
+ * The formats that the DMA controller supports, which is anything
+ * that is 8, 16, or 32 bits.
+ */
+#define FSLDMA_PCM_FORMATS (SNDRV_PCM_FMTBIT_S8 	| \
+			    SNDRV_PCM_FMTBIT_U8 	| \
+			    SNDRV_PCM_FMTBIT_S16_LE     | \
+			    SNDRV_PCM_FMTBIT_S16_BE     | \
+			    SNDRV_PCM_FMTBIT_U16_LE     | \
+			    SNDRV_PCM_FMTBIT_U16_BE     | \
+			    SNDRV_PCM_FMTBIT_S24_LE     | \
+			    SNDRV_PCM_FMTBIT_S24_BE     | \
+			    SNDRV_PCM_FMTBIT_U24_LE     | \
+			    SNDRV_PCM_FMTBIT_U24_BE     | \
+			    SNDRV_PCM_FMTBIT_S32_LE     | \
+			    SNDRV_PCM_FMTBIT_S32_BE     | \
+			    SNDRV_PCM_FMTBIT_U32_LE     | \
+			    SNDRV_PCM_FMTBIT_U32_BE)
+
+#define FSLDMA_PCM_RATES (SNDRV_PCM_RATE_5512 | SNDRV_PCM_RATE_8000_192000 | \
+			  SNDRV_PCM_RATE_CONTINUOUS)
+
+/* DMA global data.  This structure is used by fsl_dma_open() to determine
+ * which DMA channels to assign to a substream.  Unfortunately, ASoC V1 does
+ * not allow the machine driver to provide this information to the PCM
+ * driver in advance, and there's no way to differentiate between the two
+ * DMA controllers.  So for now, this driver only supports one SSI device
+ * using two DMA channels.  We cannot support multiple DMA devices.
+ *
+ * ssi_stx_phys: bus address of SSI STX register
+ * ssi_srx_phys: bus address of SSI SRX register
+ * dma_channel: pointer to the DMA channel's registers
+ * irq: IRQ for this DMA channel
+ * assigned: set to 1 if that DMA channel is assigned to a substream
+ */
+static struct {
+	dma_addr_t ssi_stx_phys;
+	dma_addr_t ssi_srx_phys;
+	struct ccsr_dma_channel __iomem *dma_channel[2];
+	unsigned int irq[2];
+	unsigned int assigned[2];
+} dma_global_data;
+
+/*
+ * The number of DMA links to use.  Two is the bare minimum, but if you
+ * have really small links you might need more.
+ */
+#define NUM_DMA_LINKS   2
+
+/** fsl_dma_private: p-substream DMA data
+ *
+ * Each substream has a 1-to-1 association with a DMA channel.
+ *
+ * The link[] array is first because it needs to be aligned on a 32-byte
+ * boundary, so putting it first will ensure alignment without padding the
+ * structure.
+ *
+ * @link[]: array of link descriptors
+ * @controller_id: which DMA controller (0, 1, ...)
+ * @channel_id: which DMA channel on the controller (0, 1, 2, ...)
+ * @dma_channel: pointer to the DMA channel's registers
+ * @irq: IRQ for this DMA channel
+ * @substream: pointer to the substream object, needed by the ISR
+ * @ssi_sxx_phys: bus address of the STX or SRX register to use
+ * @ld_buf_phys: physical address of the LD buffer
+ * @current_link: index into link[] of the link currently being processed
+ * @dma_buf_phys: physical address of the DMA buffer
+ * @dma_buf_next: physical address of the next period to process
+ * @dma_buf_end: physical address of the byte after the end of the DMA
+ * @buffer period_size: the size of a single period
+ * @num_periods: the number of periods in the DMA buffer
+ */
+struct fsl_dma_private {
+	struct fsl_dma_link_descriptor link[NUM_DMA_LINKS];
+	unsigned int controller_id;
+	unsigned int channel_id;
+	struct ccsr_dma_channel __iomem *dma_channel;
+	unsigned int irq;
+	struct snd_pcm_substream *substream;
+	dma_addr_t ssi_sxx_phys;
+	dma_addr_t ld_buf_phys;
+	unsigned int current_link;
+	dma_addr_t dma_buf_phys;
+	dma_addr_t dma_buf_next;
+	dma_addr_t dma_buf_end;
+	size_t period_size;
+	unsigned int num_periods;
+};
+
+/**
+ * fsl_dma_hardare: define characteristics of the PCM hardware.
+ *
+ * The PCM hardware is the Freescale DMA controller.  This structure defines
+ * the capabilities of that hardware.
+ *
+ * Since the sampling rate and data format are not controlled by the DMA
+ * controller, we specify no limits for those values.  The only exception is
+ * period_bytes_min, which is set to a reasonably low value to prevent the
+ * DMA controller from generating too many interrupts per second.
+ *
+ * Since each link descriptor has a 32-bit byte count field, we set
+ * period_bytes_max to the largest 32-bit number.  We also have no maximum
+ * number of periods.
+ */
+static const struct snd_pcm_hardware fsl_dma_hardware = {
+
+	.info   		= SNDRV_PCM_INFO_INTERLEAVED,
+	.formats		= FSLDMA_PCM_FORMATS,
+	.rates  		= FSLDMA_PCM_RATES,
+	.rate_min       	= 5512,
+	.rate_max       	= 192000,
+	.period_bytes_min       = 512,  	/* A reasonable limit */
+	.period_bytes_max       = (u32) -1,
+	.periods_min    	= NUM_DMA_LINKS,
+	.periods_max    	= (unsigned int) -1,
+	.buffer_bytes_max       = 128 * 1024,   /* A reasonable limit */
+};
+
+/**
+ * fsl_dma_abort_stream: tell ALSA that the DMA transfer has aborted
+ *
+ * This function should be called by the ISR whenever the DMA controller
+ * halts data transfer.
+ */
+static void fsl_dma_abort_stream(struct snd_pcm_substream *substream)
+{
+	unsigned long flags;
+
+	snd_pcm_stream_lock_irqsave(substream, flags);
+
+	if (snd_pcm_running(substream))
+		snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
+
+	snd_pcm_stream_unlock_irqrestore(substream, flags);
+}
+
+/**
+ * fsl_dma_update_pointers - update LD pointers to point to the next period
+ *
+ * As each period is completed, this function changes the the link
+ * descriptor pointers for that period to point to the next period.
+ */
+static void fsl_dma_update_pointers(struct fsl_dma_private *dma_private)
+{
+	struct fsl_dma_link_descriptor *link =
+		&dma_private->link[dma_private->current_link];
+
+	/* Update our link descriptors to point to the next period */
+	if (dma_private->substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		link->source_addr =
+			cpu_to_be32(dma_private->dma_buf_next);
+	else
+		link->dest_addr =
+			cpu_to_be32(dma_private->dma_buf_next);
+
+	/* Update our variables for next time */
+	dma_private->dma_buf_next += dma_private->period_size;
+
+	if (dma_private->dma_buf_next >= dma_private->dma_buf_end)
+		dma_private->dma_buf_next = dma_private->dma_buf_phys;
+
+	if (++dma_private->current_link >= NUM_DMA_LINKS)
+		dma_private->current_link = 0;
+}
+
+/**
+ * fsl_dma_isr: interrupt handler for the DMA controller
+ *
+ * @irq: IRQ of the DMA channel
+ * @dev_id: pointer to the dma_private structure for this DMA channel
+ */
+static irqreturn_t fsl_dma_isr(int irq, void *dev_id)
+{
+	struct fsl_dma_private *dma_private = dev_id;
+	struct ccsr_dma_channel __iomem *dma_channel = dma_private->dma_channel;
+	irqreturn_t ret = IRQ_NONE;
+	u32 sr, sr2 = 0;
+
+	/* We got an interrupt, so read the status register to see what we
+	   were interrupted for.
+	 */
+	sr = in_be32(&dma_channel->sr);
+
+	if (sr & CCSR_DMA_SR_TE) {
+		dev_err(dma_private->substream->pcm->card->dev,
+			"DMA transmit error (controller=%u channel=%u irq=%u\n",
+			dma_private->controller_id,
+			dma_private->channel_id, irq);
+		fsl_dma_abort_stream(dma_private->substream);
+		sr2 |= CCSR_DMA_SR_TE;
+		ret = IRQ_HANDLED;
+	}
+
+	if (sr & CCSR_DMA_SR_CH)
+		ret = IRQ_HANDLED;
+
+	if (sr & CCSR_DMA_SR_PE) {
+		dev_err(dma_private->substream->pcm->card->dev,
+			"DMA%u programming error (channel=%u irq=%u)\n",
+			dma_private->controller_id,
+			dma_private->channel_id, irq);
+		fsl_dma_abort_stream(dma_private->substream);
+		sr2 |= CCSR_DMA_SR_PE;
+		ret = IRQ_HANDLED;
+	}
+
+	if (sr & CCSR_DMA_SR_EOLNI) {
+		sr2 |= CCSR_DMA_SR_EOLNI;
+		ret = IRQ_HANDLED;
+	}
+
+	if (sr & CCSR_DMA_SR_CB)
+		ret = IRQ_HANDLED;
+
+	if (sr & CCSR_DMA_SR_EOSI) {
+		struct snd_pcm_substream *substream = dma_private->substream;
+
+		/* Tell ALSA we completed a period. */
+		snd_pcm_period_elapsed(substream);
+
+		/*
+		 * Update our link descriptors to point to the next period. We
+		 * only need to do this if the number of periods is not equal to
+		 * the number of links.
+		 */
+		if (dma_private->num_periods != NUM_DMA_LINKS)
+			fsl_dma_update_pointers(dma_private);
+
+		sr2 |= CCSR_DMA_SR_EOSI;
+		ret = IRQ_HANDLED;
+	}
+
+	if (sr & CCSR_DMA_SR_EOLSI) {
+		sr2 |= CCSR_DMA_SR_EOLSI;
+		ret = IRQ_HANDLED;
+	}
+
+	/* Clear the bits that we set */
+	if (sr2)
+		out_be32(&dma_channel->sr, sr2);
+
+	return ret;
+}
+
+/**
+ * fsl_dma_new: initialize this PCM driver.
+ *
+ * This function is called when the codec driver calls snd_soc_new_pcms(),
+ * once for each .dai_link in the machine driver's snd_soc_machine
+ * structure.
+ */
+static int fsl_dma_new(struct snd_card *card, struct snd_soc_codec_dai *dai,
+	struct snd_pcm *pcm)
+{
+	static u64 fsl_dma_dmamask = DMA_BIT_MASK(32);
+	int ret;
+
+	if (!card->dev->dma_mask)
+		card->dev->dma_mask = &fsl_dma_dmamask;
+
+	if (!card->dev->coherent_dma_mask)
+		card->dev->coherent_dma_mask = fsl_dma_dmamask;
+
+	ret = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV, pcm->dev,
+		fsl_dma_hardware.buffer_bytes_max,
+		&pcm->streams[0].substream->dma_buffer);
+	if (ret) {
+		dev_err(card->dev,
+			"Can't allocate playback DMA buffer (size=%u)\n",
+			fsl_dma_hardware.buffer_bytes_max);
+		return -ENOMEM;
+	}
+
+	ret = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV, pcm->dev,
+		fsl_dma_hardware.buffer_bytes_max,
+		&pcm->streams[1].substream->dma_buffer);
+	if (ret) {
+		snd_dma_free_pages(&pcm->streams[0].substream->dma_buffer);
+		dev_err(card->dev,
+			"Can't allocate capture DMA buffer (size=%u)\n",
+			fsl_dma_hardware.buffer_bytes_max);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+/**
+ * fsl_dma_open: open a new substream.
+ *
+ * Each substream has its own DMA buffer.
+ */
+static int fsl_dma_open(struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct fsl_dma_private *dma_private;
+	dma_addr_t ld_buf_phys;
+	unsigned int channel;
+	int ret = 0;
+
+	/*
+	 * Reject any DMA buffer whose size is not a multiple of the period
+	 * size.  We need to make sure that the DMA buffer can be evenly divided
+	 * into periods.
+	 */
+	ret = snd_pcm_hw_constraint_integer(runtime,
+		SNDRV_PCM_HW_PARAM_PERIODS);
+	if (ret < 0) {
+		dev_err(substream->pcm->card->dev, "invalid buffer size\n");
+		return ret;
+	}
+
+	channel = substream->stream == SNDRV_PCM_STREAM_PLAYBACK ? 0 : 1;
+
+	if (dma_global_data.assigned[channel]) {
+		dev_err(substream->pcm->card->dev,
+			"DMA channel already assigned\n");
+		return -EBUSY;
+	}
+
+	dma_private = dma_alloc_coherent(substream->pcm->dev,
+		sizeof(struct fsl_dma_private), &ld_buf_phys, GFP_KERNEL);
+	if (!dma_private) {
+		dev_err(substream->pcm->card->dev,
+			"can't allocate DMA private data\n");
+		return -ENOMEM;
+	}
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		dma_private->ssi_sxx_phys = dma_global_data.ssi_stx_phys;
+	else
+		dma_private->ssi_sxx_phys = dma_global_data.ssi_srx_phys;
+
+	dma_private->dma_channel = dma_global_data.dma_channel[channel];
+	dma_private->irq = dma_global_data.irq[channel];
+	dma_private->substream = substream;
+	dma_private->ld_buf_phys = ld_buf_phys;
+	dma_private->dma_buf_phys = substream->dma_buffer.addr;
+
+	/* We only support one DMA controller for now */
+	dma_private->controller_id = 0;
+	dma_private->channel_id = channel;
+
+	ret = request_irq(dma_private->irq, fsl_dma_isr, 0, "DMA", dma_private);
+	if (ret) {
+		dev_err(substream->pcm->card->dev,
+			"can't register ISR for IRQ %u (ret=%i)\n",
+			dma_private->irq, ret);
+		dma_free_coherent(substream->pcm->dev,
+			sizeof(struct fsl_dma_private),
+			dma_private, dma_private->ld_buf_phys);
+		return ret;
+	}
+
+	dma_global_data.assigned[channel] = 1;
+
+	snd_pcm_set_runtime_buffer(substream, &substream->dma_buffer);
+	snd_soc_set_runtime_hwparams(substream, &fsl_dma_hardware);
+	runtime->private_data = dma_private;
+
+	return 0;
+}
+
+/**
+ * fsl_dma_hw_params: allocate the DMA buffer and the DMA link descriptors.
+ *
+ * ALSA divides the DMA buffer into N periods.  We create NUM_DMA_LINKS link
+ * descriptors that ping-pong from one period to the next.  For example, if
+ * there are six periods and two link descriptors, this is how they look
+ * before playback starts:
+ *
+ *      	   The last link descriptor
+ *   ____________  points back to the first
+ *  |   	 |
+ *  V   	 |
+ *  ___    ___   |
+ * |   |->|   |->|
+ * |___|  |___|
+ *   |      |
+ *   |      |
+ *   V      V
+ *  _________________________________________
+ * |      |      |      |      |      |      |  The DMA buffer is
+ * |      |      |      |      |      |      |    divided into 6 parts
+ * |______|______|______|______|______|______|
+ *
+ * and here's how they look after the first period is finished playing:
+ *
+ *   ____________
+ *  |   	 |
+ *  V   	 |
+ *  ___    ___   |
+ * |   |->|   |->|
+ * |___|  |___|
+ *   |      |
+ *   |______________
+ *          |       |
+ *          V       V
+ *  _________________________________________
+ * |      |      |      |      |      |      |
+ * |      |      |      |      |      |      |
+ * |______|______|______|______|______|______|
+ *
+ * The first link descriptor now points to the third period.  The DMA
+ * controller is currently playing the second period.  When it finishes, it
+ * will jump back to the first descriptor and play the third period.
+ *
+ * There are four reasons we do this:
+ *
+ * 1. The only way to get the DMA controller to automatically restart the
+ *    transfer when it gets to the end of the buffer is to use chaining
+ *    mode.  Basic direct mode doesn't offer that feature.
+ * 2. We need to receive an interrupt at the end of every period.  The DMA
+ *    controller can generate an interrupt at the end of every link transfer
+ *    (aka segment).  Making each period into a DMA segment will give us the
+ *    interrupts we need.
+ * 3. By creating only two link descriptors, regardless of the number of
+ *    periods, we do not need to reallocate the link descriptors if the
+ *    number of periods changes.
+ * 4. All of the audio data is still stored in a single, contiguous DMA
+ *    buffer, which is what ALSA expects.  We're just dividing it into
+ *    contiguous parts, and creating a link descriptor for each one.
+ *
+ * Note that due to a quirk of the SSI's STX register, the target address
+ * for the DMA operations depends on the sample size.  So we don't program
+ * the dest_addr (for playback -- source_addr for capture) fields in the
+ * link descriptors here.  We do that in fsl_dma_prepare()
+ */
+static int fsl_dma_hw_params(struct snd_pcm_substream *substream,
+	struct snd_pcm_hw_params *hw_params)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct fsl_dma_private *dma_private = runtime->private_data;
+	struct ccsr_dma_channel __iomem *dma_channel = dma_private->dma_channel;
+
+	dma_addr_t temp_addr;   /* Pointer to next period */
+	u64 temp_link;  	/* Pointer to next link descriptor */
+	u32 mr; 		/* Temporary variable for MR register */
+
+	unsigned int i;
+
+	/* Get all the parameters we need */
+	size_t buffer_size = params_buffer_bytes(hw_params);
+	size_t period_size = params_period_bytes(hw_params);
+
+	/* Initialize our DMA tracking variables */
+	dma_private->period_size = period_size;
+	dma_private->num_periods = params_periods(hw_params);
+	dma_private->dma_buf_end = dma_private->dma_buf_phys + buffer_size;
+	dma_private->dma_buf_next = dma_private->dma_buf_phys +
+		(NUM_DMA_LINKS * period_size);
+	if (dma_private->dma_buf_next >= dma_private->dma_buf_end)
+		dma_private->dma_buf_next = dma_private->dma_buf_phys;
+
+	/*
+	 * Initialize each link descriptor.
+	 *
+	 * The actual address in STX0 (destination for playback, source for
+	 * capture) is based on the sample size, but we don't know the sample
+	 * size in this function, so we'll have to adjust that later.  See
+	 * comments in fsl_dma_prepare().
+	 *
+	 * The DMA controller does not have a cache, so the CPU does not
+	 * need to tell it to flush its cache.  However, the DMA
+	 * controller does need to tell the CPU to flush its cache.
+	 * That's what the SNOOP bit does.
+	 *
+	 * Also, even though the DMA controller supports 36-bit addressing, for
+	 * simplicity we currently support only 32-bit addresses for the audio
+	 * buffer itself.
+	 */
+	temp_addr = substream->dma_buffer.addr;
+	temp_link = dma_private->ld_buf_phys +
+		sizeof(struct fsl_dma_link_descriptor);
+
+	for (i = 0; i < NUM_DMA_LINKS; i++) {
+		struct fsl_dma_link_descriptor *link = &dma_private->link[i];
+
+		link->count = cpu_to_be32(period_size);
+		link->source_attr = cpu_to_be32(CCSR_DMA_ATR_SNOOP);
+		link->dest_attr = cpu_to_be32(CCSR_DMA_ATR_SNOOP);
+		link->next = cpu_to_be64(temp_link);
+
+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+			link->source_addr = cpu_to_be32(temp_addr);
+		else
+			link->dest_addr = cpu_to_be32(temp_addr);
+
+		temp_addr += period_size;
+		temp_link += sizeof(struct fsl_dma_link_descriptor);
+	}
+	/* The last link descriptor points to the first */
+	dma_private->link[i - 1].next = cpu_to_be64(dma_private->ld_buf_phys);
+
+	/* Tell the DMA controller where the first link descriptor is */
+	out_be32(&dma_channel->clndar,
+		CCSR_DMA_CLNDAR_ADDR(dma_private->ld_buf_phys));
+	out_be32(&dma_channel->eclndar,
+		CCSR_DMA_ECLNDAR_ADDR(dma_private->ld_buf_phys));
+
+	/* The manual says the BCR must be clear before enabling EMP */
+	out_be32(&dma_channel->bcr, 0);
+
+	/*
+	 * Program the mode register for interrupts, external master control,
+	 * and source/destination hold.  Also clear the Channel Abort bit.
+	 */
+	mr = in_be32(&dma_channel->mr) &
+		~(CCSR_DMA_MR_CA | CCSR_DMA_MR_DAHE | CCSR_DMA_MR_SAHE);
+
+	/*
+	 * We want External Master Start and External Master Pause enabled,
+	 * because the SSI is controlling the DMA controller.  We want the DMA
+	 * controller to be set up in advance, and then we signal only the SSI
+	 * to start transfering.
+	 *
+	 * We want End-Of-Segment Interrupts enabled, because this will generate
+	 * an interrupt at the end of each segment (each link descriptor
+	 * represents one segment).  Each DMA segment is the same thing as an
+	 * ALSA period, so this is how we get an interrupt at the end of every
+	 * period.
+	 *
+	 * We want Error Interrupt enabled, so that we can get an error if
+	 * the DMA controller is mis-programmed somehow.
+	 */
+	mr |= CCSR_DMA_MR_EOSIE | CCSR_DMA_MR_EIE | CCSR_DMA_MR_EMP_EN |
+		CCSR_DMA_MR_EMS_EN;
+
+	/* For playback, we want the destination address to be held.  For
+	   capture, set the source address to be held. */
+	mr |= (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) ?
+		CCSR_DMA_MR_DAHE : CCSR_DMA_MR_SAHE;
+
+	out_be32(&dma_channel->mr, mr);
+
+	return 0;
+}
+
+/**
+ * fsl_dma_prepare - prepare the DMA registers for playback.
+ *
+ * This function is called after the specifics of the audio data are known,
+ * i.e. snd_pcm_runtime is initialized.
+ *
+ * In this function, we finish programming the registers of the DMA
+ * controller that are dependent on the sample size.
+ *
+ * One of the drawbacks with big-endian is that when copying integers of
+ * different sizes to a fixed-sized register, the address to which the
+ * integer must be copied is dependent on the size of the integer.
+ *
+ * For example, if P is the address of a 32-bit register, and X is a 32-bit
+ * integer, then X should be copied to address P.  However, if X is a 16-bit
+ * integer, then it should be copied to P+2.  If X is an 8-bit register,
+ * then it should be copied to P+3.
+ *
+ * So for playback of 8-bit samples, the DMA controller must transfer single
+ * bytes from the DMA buffer to the last byte of the STX0 register, i.e.
+ * offset by 3 bytes. For 16-bit samples, the offset is two bytes.
+ *
+ * For 24-bit samples, the offset is 1 byte.  However, the DMA controller
+ * does not support 3-byte copies (the DAHTS register supports only 1, 2, 4,
+ * and 8 bytes at a time).  So we do not support packed 24-bit samples.
+ * 24-bit data must be padded to 32 bits.
+ */
+static int fsl_dma_prepare(struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct fsl_dma_private *dma_private = runtime->private_data;
+	struct ccsr_dma_channel __iomem *dma_channel = dma_private->dma_channel;
+	u32 mr;
+	unsigned int i;
+	dma_addr_t ssi_sxx_phys;	/* Bus address of SSI STX register */
+	unsigned int frame_size;	/* Number of bytes per frame */
+
+	ssi_sxx_phys = dma_private->ssi_sxx_phys;
+
+	mr = in_be32(&dma_channel->mr) & ~(CCSR_DMA_MR_BWC_MASK |
+		  CCSR_DMA_MR_SAHTS_MASK | CCSR_DMA_MR_DAHTS_MASK);
+
+	switch (runtime->sample_bits) {
+	case 8:
+		mr |= CCSR_DMA_MR_DAHTS_1 | CCSR_DMA_MR_SAHTS_1;
+		ssi_sxx_phys += 3;
+		break;
+	case 16:
+		mr |= CCSR_DMA_MR_DAHTS_2 | CCSR_DMA_MR_SAHTS_2;
+		ssi_sxx_phys += 2;
+		break;
+	case 32:
+		mr |= CCSR_DMA_MR_DAHTS_4 | CCSR_DMA_MR_SAHTS_4;
+		break;
+	default:
+		dev_err(substream->pcm->card->dev,
+			"unsupported sample size %u\n", runtime->sample_bits);
+		return -EINVAL;
+	}
+
+	frame_size = runtime->frame_bits / 8;
+	/*
+	 * BWC should always be a multiple of the frame size.  BWC determines
+	 * how many bytes are sent/received before the DMA controller checks the
+	 * SSI to see if it needs to stop.  For playback, the transmit FIFO can
+	 * hold three frames, so we want to send two frames at a time. For
+	 * capture, the receive FIFO is triggered when it contains one frame, so
+	 * we want to receive one frame at a time.
+	 */
+
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		mr |= CCSR_DMA_MR_BWC(2 * frame_size);
+	else
+		mr |= CCSR_DMA_MR_BWC(frame_size);
+
+	out_be32(&dma_channel->mr, mr);
+
+	/*
+	 * Program the address of the DMA transfer to/from the SSI.
+	 */
+	for (i = 0; i < NUM_DMA_LINKS; i++) {
+		struct fsl_dma_link_descriptor *link = &dma_private->link[i];
+
+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+			link->dest_addr = cpu_to_be32(ssi_sxx_phys);
+		else
+			link->source_addr = cpu_to_be32(ssi_sxx_phys);
+	}
+
+	return 0;
+}
+
+/**
+ * fsl_dma_pointer: determine the current position of the DMA transfer
+ *
+ * This function is called by ALSA when ALSA wants to know where in the
+ * stream buffer the hardware currently is.
+ *
+ * For playback, the SAR register contains the physical address of the most
+ * recent DMA transfer.  For capture, the value is in the DAR register.
+ *
+ * The base address of the buffer is stored in the source_addr field of the
+ * first link descriptor.
+ */
+static snd_pcm_uframes_t fsl_dma_pointer(struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct fsl_dma_private *dma_private = runtime->private_data;
+	struct ccsr_dma_channel __iomem *dma_channel = dma_private->dma_channel;
+	dma_addr_t position;
+	snd_pcm_uframes_t frames;
+
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		position = in_be32(&dma_channel->sar);
+	else
+		position = in_be32(&dma_channel->dar);
+
+	frames = bytes_to_frames(runtime, position - dma_private->dma_buf_phys);
+
+	/*
+	 * If the current address is just past the end of the buffer, wrap it
+	 * around.
+	 */
+	if (frames == runtime->buffer_size)
+		frames = 0;
+
+	return frames;
+}
+
+/**
+ * fsl_dma_hw_free: release resources allocated in fsl_dma_hw_params()
+ *
+ * Release the resources allocated in fsl_dma_hw_params() and de-program the
+ * registers.
+ *
+ * This function can be called multiple times.
+ */
+static int fsl_dma_hw_free(struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct fsl_dma_private *dma_private = runtime->private_data;
+
+	if (dma_private) {
+		struct ccsr_dma_channel __iomem *dma_channel;
+
+		dma_channel = dma_private->dma_channel;
+
+		/* Stop the DMA */
+		out_be32(&dma_channel->mr, CCSR_DMA_MR_CA);
+		out_be32(&dma_channel->mr, 0);
+
+		/* Reset all the other registers */
+		out_be32(&dma_channel->sr, -1);
+		out_be32(&dma_channel->clndar, 0);
+		out_be32(&dma_channel->eclndar, 0);
+		out_be32(&dma_channel->satr, 0);
+		out_be32(&dma_channel->sar, 0);
+		out_be32(&dma_channel->datr, 0);
+		out_be32(&dma_channel->dar, 0);
+		out_be32(&dma_channel->bcr, 0);
+		out_be32(&dma_channel->nlndar, 0);
+		out_be32(&dma_channel->enlndar, 0);
+	}
+
+	return 0;
+}
+
+/**
+ * fsl_dma_close: close the stream.
+ */
+static int fsl_dma_close(struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct fsl_dma_private *dma_private = runtime->private_data;
+	int dir = substream->stream == SNDRV_PCM_STREAM_PLAYBACK ? 0 : 1;
+
+	if (dma_private) {
+		if (dma_private->irq)
+			free_irq(dma_private->irq, dma_private);
+
+		if (dma_private->ld_buf_phys) {
+			dma_unmap_single(substream->pcm->dev,
+				dma_private->ld_buf_phys,
+				sizeof(dma_private->link), DMA_TO_DEVICE);
+		}
+
+		/* Deallocate the fsl_dma_private structure */
+		dma_free_coherent(substream->pcm->dev,
+			sizeof(struct fsl_dma_private),
+			dma_private, dma_private->ld_buf_phys);
+		substream->runtime->private_data = NULL;
+	}
+
+	dma_global_data.assigned[dir] = 0;
+
+	return 0;
+}
+
+/*
+ * Remove this PCM driver.
+ */
+static void fsl_dma_free_dma_buffers(struct snd_pcm *pcm)
+{
+	struct snd_pcm_substream *substream;
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(pcm->streams); i++) {
+		substream = pcm->streams[i].substream;
+		if (substream) {
+			snd_dma_free_pages(&substream->dma_buffer);
+			substream->dma_buffer.area = NULL;
+			substream->dma_buffer.addr = 0;
+		}
+	}
+}
+
+static struct snd_pcm_ops fsl_dma_ops = {
+	.open   	= fsl_dma_open,
+	.close  	= fsl_dma_close,
+	.ioctl  	= snd_pcm_lib_ioctl,
+	.hw_params      = fsl_dma_hw_params,
+	.hw_free	= fsl_dma_hw_free,
+	.prepare	= fsl_dma_prepare,
+	.pointer	= fsl_dma_pointer,
+};
+
+struct snd_soc_platform fsl_soc_platform = {
+	.name   	= "fsl-dma",
+	.pcm_ops	= &fsl_dma_ops,
+	.pcm_new	= fsl_dma_new,
+	.pcm_free       = fsl_dma_free_dma_buffers,
+};
+EXPORT_SYMBOL_GPL(fsl_soc_platform);
+
+/**
+ * fsl_dma_configure: store the DMA parameters from the fabric driver.
+ *
+ * This function is called by the ASoC fabric driver to give us the DMA and
+ * SSI channel information.
+ *
+ * Unfortunately, ASoC V1 does make it possible to determine the DMA/SSI
+ * data when a substream is created, so for now we need to store this data
+ * into a global variable.  This means that we can only support one DMA
+ * controller, and hence only one SSI.
+ */
+int fsl_dma_configure(struct fsl_dma_info *dma_info)
+{
+	static int initialized;
+
+	/* We only support one DMA controller for now */
+	if (initialized)
+		return 0;
+
+	dma_global_data.ssi_stx_phys = dma_info->ssi_stx_phys;
+	dma_global_data.ssi_srx_phys = dma_info->ssi_srx_phys;
+	dma_global_data.dma_channel[0] = dma_info->dma_channel[0];
+	dma_global_data.dma_channel[1] = dma_info->dma_channel[1];
+	dma_global_data.irq[0] = dma_info->dma_irq[0];
+	dma_global_data.irq[1] = dma_info->dma_irq[1];
+	dma_global_data.assigned[0] = 0;
+	dma_global_data.assigned[1] = 0;
+
+	initialized = 1;
+	return 1;
+}
+EXPORT_SYMBOL_GPL(fsl_dma_configure);
+
+MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
+MODULE_DESCRIPTION("Freescale Elo DMA ASoC PCM module");
+MODULE_LICENSE("GPL");