Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 921 insertions, 0 deletions

diff --git a/sound/soc/fsl/fsl_dma.c b/sound/soc/fsl/fsl_dma.c
new file mode 100644
index 0000000000..963f9774c8
--- /dev/null
+++ b/sound/soc/fsl/fsl_dma.c
@@ -0,0 +1,921 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Freescale DMA ALSA SoC PCM driver
+//
+// Author: Timur Tabi <timur@freescale.com>
+//
+// Copyright 2007-2010 Freescale Semiconductor, Inc.
+//
+// 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 <linux/gfp.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/of_platform.h>
+#include <linux/list.h>
+#include <linux/slab.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"
+#include "fsl_ssi.h"	/* For the offset of stx0 and srx0 */
+
+#define DRV_NAME "fsl_dma"
+
+/*
+ * 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)
+struct dma_object {
+	struct snd_soc_component_driver dai;
+	dma_addr_t ssi_stx_phys;
+	dma_addr_t ssi_srx_phys;
+	unsigned int ssi_fifo_depth;
+	struct ccsr_dma_channel __iomem *channel;
+	unsigned int irq;
+	bool assigned;
+};
+
+/*
+ * 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
+ * @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];
+	struct ccsr_dma_channel __iomem *dma_channel;
+	unsigned int irq;
+	struct snd_pcm_substream *substream;
+	dma_addr_t ssi_sxx_phys;
+	unsigned int ssi_fifo_depth;
+	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.
+ *
+ * Note that we specify SNDRV_PCM_INFO_JOINT_DUPLEX here, but only because a
+ * limitation in the SSI driver requires the sample rates for playback and
+ * capture to be the same.
+ */
+static const struct snd_pcm_hardware fsl_dma_hardware = {
+
+	.info   		= SNDRV_PCM_INFO_INTERLEAVED |
+				  SNDRV_PCM_INFO_MMAP |
+				  SNDRV_PCM_INFO_MMAP_VALID |
+				  SNDRV_PCM_INFO_JOINT_DUPLEX |
+				  SNDRV_PCM_INFO_PAUSE,
+	.formats		= FSLDMA_PCM_FORMATS,
+	.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)
+{
+	snd_pcm_stop_xrun(substream);
+}
+
+/**
+ * fsl_dma_update_pointers - update LD pointers to point to the next period
+ *
+ * As each period is completed, this function changes 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. On a 36-bit
+	 * system, we also need to update the ESAD bits.  We also set (keep) the
+	 * snoop bits.  See the comments in fsl_dma_hw_params() about snooping.
+	 */
+	if (dma_private->substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
+		link->source_addr = cpu_to_be32(dma_private->dma_buf_next);
+#ifdef CONFIG_PHYS_64BIT
+		link->source_attr = cpu_to_be32(CCSR_DMA_ATR_SNOOP |
+			upper_32_bits(dma_private->dma_buf_next));
+#endif
+	} else {
+		link->dest_addr = cpu_to_be32(dma_private->dma_buf_next);
+#ifdef CONFIG_PHYS_64BIT
+		link->dest_attr = cpu_to_be32(CCSR_DMA_ATR_SNOOP |
+			upper_32_bits(dma_private->dma_buf_next));
+#endif
+	}
+
+	/* 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 snd_pcm_substream *substream = dma_private->substream;
+	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
+	struct device *dev = rtd->dev;
+	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(dev, "dma transmit error\n");
+		fsl_dma_abort_stream(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(dev, "dma programming error\n");
+		fsl_dma_abort_stream(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) {
+		/* 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_card
+ * structure.
+ *
+ * snd_dma_alloc_pages() is just a front-end to dma_alloc_coherent(), which
+ * (currently) always allocates the DMA buffer in lowmem, even if GFP_HIGHMEM
+ * is specified. Therefore, any DMA buffers we allocate will always be in low
+ * memory, but we support for 36-bit physical addresses anyway.
+ *
+ * Regardless of where the memory is actually allocated, since the device can
+ * technically DMA to any 36-bit address, we do need to set the DMA mask to 36.
+ */
+static int fsl_dma_new(struct snd_soc_component *component,
+		       struct snd_soc_pcm_runtime *rtd)
+{
+	struct snd_card *card = rtd->card->snd_card;
+	struct snd_pcm *pcm = rtd->pcm;
+	int ret;
+
+	ret = dma_coerce_mask_and_coherent(card->dev, DMA_BIT_MASK(36));
+	if (ret)
+		return ret;
+
+	return snd_pcm_set_fixed_buffer_all(pcm, SNDRV_DMA_TYPE_DEV,
+					    card->dev,
+					    fsl_dma_hardware.buffer_bytes_max);
+}
+
+/**
+ * fsl_dma_open: open a new substream.
+ *
+ * Each substream has its own DMA buffer.
+ *
+ * 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.
+ */
+static int fsl_dma_open(struct snd_soc_component *component,
+			struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct device *dev = component->dev;
+	struct dma_object *dma =
+		container_of(component->driver, struct dma_object, dai);
+	struct fsl_dma_private *dma_private;
+	struct ccsr_dma_channel __iomem *dma_channel;
+	dma_addr_t ld_buf_phys;
+	u64 temp_link;  	/* Pointer to next link descriptor */
+	u32 mr;
+	int ret = 0;
+	unsigned int i;
+
+	/*
+	 * 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(dev, "invalid buffer size\n");
+		return ret;
+	}
+
+	if (dma->assigned) {
+		dev_err(dev, "dma channel already assigned\n");
+		return -EBUSY;
+	}
+
+	dma_private = dma_alloc_coherent(dev, sizeof(struct fsl_dma_private),
+					 &ld_buf_phys, GFP_KERNEL);
+	if (!dma_private) {
+		dev_err(dev, "can't allocate dma private data\n");
+		return -ENOMEM;
+	}
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		dma_private->ssi_sxx_phys = dma->ssi_stx_phys;
+	else
+		dma_private->ssi_sxx_phys = dma->ssi_srx_phys;
+
+	dma_private->ssi_fifo_depth = dma->ssi_fifo_depth;
+	dma_private->dma_channel = dma->channel;
+	dma_private->irq = dma->irq;
+	dma_private->substream = substream;
+	dma_private->ld_buf_phys = ld_buf_phys;
+	dma_private->dma_buf_phys = substream->dma_buffer.addr;
+
+	ret = request_irq(dma_private->irq, fsl_dma_isr, 0, "fsldma-audio",
+			  dma_private);
+	if (ret) {
+		dev_err(dev, "can't register ISR for IRQ %u (ret=%i)\n",
+			dma_private->irq, ret);
+		dma_free_coherent(dev, sizeof(struct fsl_dma_private),
+			dma_private, dma_private->ld_buf_phys);
+		return ret;
+	}
+
+	dma->assigned = true;
+
+	snd_soc_set_runtime_hwparams(substream, &fsl_dma_hardware);
+	runtime->private_data = dma_private;
+
+	/* Program the fixed DMA controller parameters */
+
+	dma_channel = dma_private->dma_channel;
+
+	temp_link = dma_private->ld_buf_phys +
+		sizeof(struct fsl_dma_link_descriptor);
+
+	for (i = 0; i < NUM_DMA_LINKS; i++) {
+		dma_private->link[i].next = cpu_to_be64(temp_link);
+
+		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 transferring.
+	 *
+	 * 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_hw_params: continue initializing the DMA links
+ *
+ * This function obtains hardware parameters about the opened stream and
+ * programs the DMA controller accordingly.
+ *
+ * One drawback of 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_hw_params(struct snd_soc_component *component,
+			     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 device *dev = component->dev;
+
+	/* Number of bits per sample */
+	unsigned int sample_bits =
+		snd_pcm_format_physical_width(params_format(hw_params));
+
+	/* Number of bytes per frame */
+	unsigned int sample_bytes = sample_bits / 8;
+
+	/* Bus address of SSI STX register */
+	dma_addr_t ssi_sxx_phys = dma_private->ssi_sxx_phys;
+
+	/* Size of the DMA buffer, in bytes */
+	size_t buffer_size = params_buffer_bytes(hw_params);
+
+	/* Number of bytes per period */
+	size_t period_size = params_period_bytes(hw_params);
+
+	/* Pointer to next period */
+	dma_addr_t temp_addr = substream->dma_buffer.addr;
+
+	/* Pointer to DMA controller */
+	struct ccsr_dma_channel __iomem *dma_channel = dma_private->dma_channel;
+
+	u32 mr; /* DMA Mode Register */
+
+	unsigned int i;
+
+	/* 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)
+		/* This happens if the number of periods == NUM_DMA_LINKS */
+		dma_private->dma_buf_next = dma_private->dma_buf_phys;
+
+	mr = in_be32(&dma_channel->mr) & ~(CCSR_DMA_MR_BWC_MASK |
+		  CCSR_DMA_MR_SAHTS_MASK | CCSR_DMA_MR_DAHTS_MASK);
+
+	/* Due to a quirk of the SSI's STX register, the target address
+	 * for the DMA operations depends on the sample size.  So we calculate
+	 * that offset here.  While we're at it, also tell the DMA controller
+	 * how much data to transfer per sample.
+	 */
+	switch (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:
+		/* We should never get here */
+		dev_err(dev, "unsupported sample size %u\n", sample_bits);
+		return -EINVAL;
+	}
+
+	/*
+	 * BWC determines how many bytes are sent/received before the DMA
+	 * controller checks the SSI to see if it needs to stop. BWC should
+	 * always be a multiple of the frame size, so that we always transmit
+	 * whole frames.  Each frame occupies two slots in the FIFO.  The
+	 * parameter for CCSR_DMA_MR_BWC() is rounded down the next power of two
+	 * (MR[BWC] can only represent even powers of two).
+	 *
+	 * To simplify the process, we set BWC to the largest value that is
+	 * less than or equal to the FIFO watermark.  For playback, this ensures
+	 * that we transfer the maximum amount without overrunning the FIFO.
+	 * For capture, this ensures that we transfer the maximum amount without
+	 * underrunning the FIFO.
+	 *
+	 * f = SSI FIFO depth
+	 * w = SSI watermark value (which equals f - 2)
+	 * b = DMA bandwidth count (in bytes)
+	 * s = sample size (in bytes, which equals frame_size * 2)
+	 *
+	 * For playback, we never transmit more than the transmit FIFO
+	 * watermark, otherwise we might write more data than the FIFO can hold.
+	 * The watermark is equal to the FIFO depth minus two.
+	 *
+	 * For capture, two equations must hold:
+	 *	w > f - (b / s)
+	 *	w >= b / s
+	 *
+	 * So, b > 2 * s, but b must also be <= s * w.  To simplify, we set
+	 * b = s * w, which is equal to
+	 *      (dma_private->ssi_fifo_depth - 2) * sample_bytes.
+	 */
+	mr |= CCSR_DMA_MR_BWC((dma_private->ssi_fifo_depth - 2) * sample_bytes);
+
+	out_be32(&dma_channel->mr, mr);
+
+	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);
+
+		/* The snoop bit tells the DMA controller whether it should tell
+		 * the ECM to snoop during a read or write to an address. For
+		 * audio, we use DMA to transfer data between memory and an I/O
+		 * device (the SSI's STX0 or SRX0 register). Snooping is only
+		 * needed if there is a cache, so we need to snoop memory
+		 * addresses only.  For playback, that means we snoop the source
+		 * but not the destination.  For capture, we snoop the
+		 * destination but not the source.
+		 *
+		 * Note that failing to snoop properly is unlikely to cause
+		 * cache incoherency if the period size is larger than the
+		 * size of L1 cache.  This is because filling in one period will
+		 * flush out the data for the previous period.  So if you
+		 * increased period_bytes_min to a large enough size, you might
+		 * get more performance by not snooping, and you'll still be
+		 * okay.  You'll need to update fsl_dma_update_pointers() also.
+		 */
+		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
+			link->source_addr = cpu_to_be32(temp_addr);
+			link->source_attr = cpu_to_be32(CCSR_DMA_ATR_SNOOP |
+				upper_32_bits(temp_addr));
+
+			link->dest_addr = cpu_to_be32(ssi_sxx_phys);
+			link->dest_attr = cpu_to_be32(CCSR_DMA_ATR_NOSNOOP |
+				upper_32_bits(ssi_sxx_phys));
+		} else {
+			link->source_addr = cpu_to_be32(ssi_sxx_phys);
+			link->source_attr = cpu_to_be32(CCSR_DMA_ATR_NOSNOOP |
+				upper_32_bits(ssi_sxx_phys));
+
+			link->dest_addr = cpu_to_be32(temp_addr);
+			link->dest_attr = cpu_to_be32(CCSR_DMA_ATR_SNOOP |
+				upper_32_bits(temp_addr));
+		}
+
+		temp_addr += period_size;
+	}
+
+	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_soc_component *component,
+					 struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct fsl_dma_private *dma_private = runtime->private_data;
+	struct device *dev = component->dev;
+	struct ccsr_dma_channel __iomem *dma_channel = dma_private->dma_channel;
+	dma_addr_t position;
+	snd_pcm_uframes_t frames;
+
+	/* Obtain the current DMA pointer, but don't read the ESAD bits if we
+	 * only have 32-bit DMA addresses.  This function is typically called
+	 * in interrupt context, so we need to optimize it.
+	 */
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
+		position = in_be32(&dma_channel->sar);
+#ifdef CONFIG_PHYS_64BIT
+		position |= (u64)(in_be32(&dma_channel->satr) &
+				  CCSR_DMA_ATR_ESAD_MASK) << 32;
+#endif
+	} else {
+		position = in_be32(&dma_channel->dar);
+#ifdef CONFIG_PHYS_64BIT
+		position |= (u64)(in_be32(&dma_channel->datr) &
+				  CCSR_DMA_ATR_ESAD_MASK) << 32;
+#endif
+	}
+
+	/*
+	 * When capture is started, the SSI immediately starts to fill its FIFO.
+	 * This means that the DMA controller is not started until the FIFO is
+	 * full.  However, ALSA calls this function before that happens, when
+	 * MR.DAR is still zero.  In this case, just return zero to indicate
+	 * that nothing has been received yet.
+	 */
+	if (!position)
+		return 0;
+
+	if ((position < dma_private->dma_buf_phys) ||
+	    (position > dma_private->dma_buf_end)) {
+		dev_err(dev, "dma pointer is out of range, halting stream\n");
+		return SNDRV_PCM_POS_XRUN;
+	}
+
+	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_soc_component *component,
+			   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_soc_component *component,
+			 struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct fsl_dma_private *dma_private = runtime->private_data;
+	struct device *dev = component->dev;
+	struct dma_object *dma =
+		container_of(component->driver, struct dma_object, dai);
+
+	if (dma_private) {
+		if (dma_private->irq)
+			free_irq(dma_private->irq, dma_private);
+
+		/* Deallocate the fsl_dma_private structure */
+		dma_free_coherent(dev, sizeof(struct fsl_dma_private),
+				  dma_private, dma_private->ld_buf_phys);
+		substream->runtime->private_data = NULL;
+	}
+
+	dma->assigned = false;
+
+	return 0;
+}
+
+/**
+ * find_ssi_node -- returns the SSI node that points to its DMA channel node
+ *
+ * Although this DMA driver attempts to operate independently of the other
+ * devices, it still needs to determine some information about the SSI device
+ * that it's working with.  Unfortunately, the device tree does not contain
+ * a pointer from the DMA channel node to the SSI node -- the pointer goes the
+ * other way.  So we need to scan the device tree for SSI nodes until we find
+ * the one that points to the given DMA channel node.  It's ugly, but at least
+ * it's contained in this one function.
+ */
+static struct device_node *find_ssi_node(struct device_node *dma_channel_np)
+{
+	struct device_node *ssi_np, *np;
+
+	for_each_compatible_node(ssi_np, NULL, "fsl,mpc8610-ssi") {
+		/* Check each DMA phandle to see if it points to us.  We
+		 * assume that device_node pointers are a valid comparison.
+		 */
+		np = of_parse_phandle(ssi_np, "fsl,playback-dma", 0);
+		of_node_put(np);
+		if (np == dma_channel_np)
+			return ssi_np;
+
+		np = of_parse_phandle(ssi_np, "fsl,capture-dma", 0);
+		of_node_put(np);
+		if (np == dma_channel_np)
+			return ssi_np;
+	}
+
+	return NULL;
+}
+
+static int fsl_soc_dma_probe(struct platform_device *pdev)
+{
+	struct dma_object *dma;
+	struct device_node *np = pdev->dev.of_node;
+	struct device_node *ssi_np;
+	struct resource res;
+	const uint32_t *iprop;
+	int ret;
+
+	/* Find the SSI node that points to us. */
+	ssi_np = find_ssi_node(np);
+	if (!ssi_np) {
+		dev_err(&pdev->dev, "cannot find parent SSI node\n");
+		return -ENODEV;
+	}
+
+	ret = of_address_to_resource(ssi_np, 0, &res);
+	if (ret) {
+		dev_err(&pdev->dev, "could not determine resources for %pOF\n",
+			ssi_np);
+		of_node_put(ssi_np);
+		return ret;
+	}
+
+	dma = kzalloc(sizeof(*dma), GFP_KERNEL);
+	if (!dma) {
+		of_node_put(ssi_np);
+		return -ENOMEM;
+	}
+
+	dma->dai.name = DRV_NAME;
+	dma->dai.open = fsl_dma_open;
+	dma->dai.close = fsl_dma_close;
+	dma->dai.hw_params = fsl_dma_hw_params;
+	dma->dai.hw_free = fsl_dma_hw_free;
+	dma->dai.pointer = fsl_dma_pointer;
+	dma->dai.pcm_construct = fsl_dma_new;
+
+	/* Store the SSI-specific information that we need */
+	dma->ssi_stx_phys = res.start + REG_SSI_STX0;
+	dma->ssi_srx_phys = res.start + REG_SSI_SRX0;
+
+	iprop = of_get_property(ssi_np, "fsl,fifo-depth", NULL);
+	if (iprop)
+		dma->ssi_fifo_depth = be32_to_cpup(iprop);
+	else
+                /* Older 8610 DTs didn't have the fifo-depth property */
+		dma->ssi_fifo_depth = 8;
+
+	of_node_put(ssi_np);
+
+	ret = devm_snd_soc_register_component(&pdev->dev, &dma->dai, NULL, 0);
+	if (ret) {
+		dev_err(&pdev->dev, "could not register platform\n");
+		kfree(dma);
+		return ret;
+	}
+
+	dma->channel = of_iomap(np, 0);
+	dma->irq = irq_of_parse_and_map(np, 0);
+
+	dev_set_drvdata(&pdev->dev, dma);
+
+	return 0;
+}
+
+static void fsl_soc_dma_remove(struct platform_device *pdev)
+{
+	struct dma_object *dma = dev_get_drvdata(&pdev->dev);
+
+	iounmap(dma->channel);
+	irq_dispose_mapping(dma->irq);
+	kfree(dma);
+}
+
+static const struct of_device_id fsl_soc_dma_ids[] = {
+	{ .compatible = "fsl,ssi-dma-channel", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, fsl_soc_dma_ids);
+
+static struct platform_driver fsl_soc_dma_driver = {
+	.driver = {
+		.name = "fsl-pcm-audio",
+		.of_match_table = fsl_soc_dma_ids,
+	},
+	.probe = fsl_soc_dma_probe,
+	.remove_new = fsl_soc_dma_remove,
+};
+
+module_platform_driver(fsl_soc_dma_driver);
+
+MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
+MODULE_DESCRIPTION("Freescale Elo DMA ASoC PCM Driver");
+MODULE_LICENSE("GPL v2");