If an OSS application calls SNDCTL_DSP_SYNC, then ALSA will call the driver's
_hw_params and _prepare functions again. On the Freescale MPC8610 DMA ASoC
driver, this caused the DMA controller to be unneccessarily re-programmed, and
apparently it doesn't like that. The DMA will then not operate when
instructed. This patch relocates much of the DMA programming to
fsl_dma_open(), which is called only once.
Signed-off-by: Timur Tabi <timur(a)freescale.com>
---
This patch is for 2.6.27. A separate patch for ASoC V2 will be posted later.
sound/soc/fsl/fsl_dma.c | 235 +++++++++++++++++++++++++----------------------
1 files changed, 124 insertions(+), 111 deletions(-)
diff --git a/sound/soc/fsl/fsl_dma.c b/sound/soc/fsl/fsl_dma.c
index 7ceea2b..d2d3da9 100644
--- a/sound/soc/fsl/fsl_dma.c
+++ b/sound/soc/fsl/fsl_dma.c
@@ -327,14 +327,75 @@ static int fsl_dma_new(struct snd_card *card, struct snd_soc_dai *dai,
* 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_pcm_substream *substream)
{
struct snd_pcm_runtime *runtime = substream->runtime;
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;
unsigned int channel;
int ret = 0;
+ unsigned int i;
/*
* Reject any DMA buffer whose size is not a multiple of the period
@@ -395,68 +456,74 @@ static int fsl_dma_open(struct snd_pcm_substream *substream)
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++) {
+ struct fsl_dma_link_descriptor *link = &dma_private->link[i];
+
+ 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);
+
+ 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: 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
- * _________________________________________
- * | | | | | | |
- * | | | | | | |
- * |______|______|______|______|______|______|
+ * fsl_dma_hw_params: continue initializing the DMA links
*
- * 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.
+ * This function obtains hardware parameters about the opened stream and
+ * programs the DMA controller accordingly.
*
* 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
@@ -468,11 +535,8 @@ static int fsl_dma_hw_params(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 temp_addr; /* Pointer to next period */
- u64 temp_link; /* Pointer to next link descriptor */
- u32 mr; /* Temporary variable for MR register */
unsigned int i;
@@ -490,8 +554,6 @@ static int fsl_dma_hw_params(struct snd_pcm_substream *substream,
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
@@ -507,16 +569,11 @@ static int fsl_dma_hw_params(struct snd_pcm_substream *substream,
* 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);
@@ -524,51 +581,7 @@ static int fsl_dma_hw_params(struct snd_pcm_substream *substream,
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;
}
--
1.5.5
