[RFC PATCH v2 0/3] ASoC: fsl_asrc_dma: Reuse the dma channel if available in Back-End

[RFC PATCH v2 0/3] ASoC: fsl_asrc_dma: Reuse the dma channel if available in Back-End

[Shengjiu Wang]

Reuse the dma channel if available in Back-End

Shengjiu Wang (3):
  ASoC: soc-card: export snd_soc_lookup_component_nolocked
  ASoC: dmaengine_pcm: export soc_component_to_pcm
  ASoC: fsl_asrc_dma: Reuse the dma channel if available in Back-End

changes in v2:
- update according to Mark's comments and split the patch


 include/sound/dmaengine_pcm.h         | 11 ++++++
 include/sound/soc.h                   |  2 ++
 sound/soc/fsl/fsl_asrc_common.h       |  2 ++
 sound/soc/fsl/fsl_asrc_dma.c          | 52 ++++++++++++++++++++-------
 sound/soc/soc-core.c                  |  3 +-
 sound/soc/soc-generic-dmaengine-pcm.c | 12 -------
 6 files changed, 57 insertions(+), 25 deletions(-)

-- 
2.21.0

[RFC PATCH v2 1/3] ASoC: soc-card: export snd_soc_lookup_component_nolocked

[Shengjiu Wang]

snd_soc_lookup_component_nolocked can be used for the DPCM case
that Front-End needs to get the unused platform component but
added by Back-End cpu dai driver.

If the component is gotten, then we can get the dma chan created
by Back-End component and reused it in Front-End.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
---
 include/sound/soc.h  | 2 ++
 sound/soc/soc-core.c | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/sound/soc.h b/include/sound/soc.h
index 74868436ac79..565612a8d690 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -444,6 +444,8 @@ int devm_snd_soc_register_component(struct device *dev,
 			 const struct snd_soc_component_driver *component_driver,
 			 struct snd_soc_dai_driver *dai_drv, int num_dai);
 void snd_soc_unregister_component(struct device *dev);
+struct snd_soc_component *snd_soc_lookup_component_nolocked(struct device *dev,
+							    const char *driver_name);
 struct snd_soc_component *snd_soc_lookup_component(struct device *dev,
 						   const char *driver_name);
 
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index b07eca2c6ccc..d4c73e86d058 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -310,7 +310,7 @@ struct snd_soc_component *snd_soc_rtdcom_lookup(struct snd_soc_pcm_runtime *rtd,
 }
 EXPORT_SYMBOL_GPL(snd_soc_rtdcom_lookup);
 
-static struct snd_soc_component
+struct snd_soc_component
 *snd_soc_lookup_component_nolocked(struct device *dev, const char *driver_name)
 {
 	struct snd_soc_component *component;
@@ -329,6 +329,7 @@ static struct snd_soc_component
 
 	return found_component;
 }
+EXPORT_SYMBOL_GPL(snd_soc_lookup_component_nolocked);
 
 struct snd_soc_component *snd_soc_lookup_component(struct device *dev,
 						   const char *driver_name)
-- 
2.21.0

[RFC PATCH v2 2/3] ASoC: dmaengine_pcm: export soc_component_to_pcm

[Shengjiu Wang]

In DPCM case, Front-End needs to get the dma chan which has
been requested by Back-End and reuse it.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
---
 include/sound/dmaengine_pcm.h         | 11 +++++++++++
 sound/soc/soc-generic-dmaengine-pcm.c | 12 ------------
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/include/sound/dmaengine_pcm.h b/include/sound/dmaengine_pcm.h
index b65220685920..8c5e38180fb0 100644
--- a/include/sound/dmaengine_pcm.h
+++ b/include/sound/dmaengine_pcm.h
@@ -161,4 +161,15 @@ int snd_dmaengine_pcm_prepare_slave_config(struct snd_pcm_substream *substream,
 
 #define SND_DMAENGINE_PCM_DRV_NAME "snd_dmaengine_pcm"
 
+struct dmaengine_pcm {
+	struct dma_chan *chan[SNDRV_PCM_STREAM_LAST + 1];
+	const struct snd_dmaengine_pcm_config *config;
+	struct snd_soc_component component;
+	unsigned int flags;
+};
+
+static inline struct dmaengine_pcm *soc_component_to_pcm(struct snd_soc_component *p)
+{
+	return container_of(p, struct dmaengine_pcm, component);
+}
 #endif
diff --git a/sound/soc/soc-generic-dmaengine-pcm.c b/sound/soc/soc-generic-dmaengine-pcm.c
index f728309a0833..80a4e71f2d95 100644
--- a/sound/soc/soc-generic-dmaengine-pcm.c
+++ b/sound/soc/soc-generic-dmaengine-pcm.c
@@ -21,18 +21,6 @@
  */
 #define SND_DMAENGINE_PCM_FLAG_NO_RESIDUE BIT(31)
 
-struct dmaengine_pcm {
-	struct dma_chan *chan[SNDRV_PCM_STREAM_LAST + 1];
-	const struct snd_dmaengine_pcm_config *config;
-	struct snd_soc_component component;
-	unsigned int flags;
-};
-
-static struct dmaengine_pcm *soc_component_to_pcm(struct snd_soc_component *p)
-{
-	return container_of(p, struct dmaengine_pcm, component);
-}
-
 static struct device *dmaengine_dma_dev(struct dmaengine_pcm *pcm,
 	struct snd_pcm_substream *substream)
 {
-- 
2.21.0

[RFC PATCH v2 3/3] ASoC: fsl_asrc_dma: Reuse the dma channel if available in Back-End

[Shengjiu Wang]

The dma channel has been requested by Back-End cpu dai driver already.
If fsl_asrc_dma requests dma chan with same dma:tx symlink, then
there will be below warning with SDMA.

[   48.174236] fsl-esai-dai 2024000.esai: Cannot create DMA dma:tx symlink

or with EDMA the request operation will fail for EDMA channel
can only be requested once.

So If we can reuse the dma channel of Back-End, then the issue can be
fixed.

In order to get the dma channel which is already requested in Back-End.
we use the exported two functions (snd_soc_lookup_component_nolocked
and soc_component_to_pcm). If we can get the dma channel, then reuse it,
if can't, then request a new one.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
---
 sound/soc/fsl/fsl_asrc_common.h |  2 ++
 sound/soc/fsl/fsl_asrc_dma.c    | 52 +++++++++++++++++++++++++--------
 2 files changed, 42 insertions(+), 12 deletions(-)

diff --git a/sound/soc/fsl/fsl_asrc_common.h b/sound/soc/fsl/fsl_asrc_common.h
index 77665b15c8db..09512bc79b80 100644
--- a/sound/soc/fsl/fsl_asrc_common.h
+++ b/sound/soc/fsl/fsl_asrc_common.h
@@ -32,6 +32,7 @@ enum asrc_pair_index {
  * @dma_chan: inputer and output DMA channels
  * @dma_data: private dma data
  * @pos: hardware pointer position
+ * @req_dma_chan_dev_to_dev: flag for release dev_to_dev chan
  * @private: pair private area
  */
 struct fsl_asrc_pair {
@@ -45,6 +46,7 @@ struct fsl_asrc_pair {
 	struct dma_chan *dma_chan[2];
 	struct imx_dma_data dma_data;
 	unsigned int pos;
+	bool req_dma_chan_dev_to_dev;
 
 	void *private;
 };
diff --git a/sound/soc/fsl/fsl_asrc_dma.c b/sound/soc/fsl/fsl_asrc_dma.c
index d6a3fc5f87e5..5ecb77d466d3 100644
--- a/sound/soc/fsl/fsl_asrc_dma.c
+++ b/sound/soc/fsl/fsl_asrc_dma.c
@@ -133,6 +133,7 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 	bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
 	struct snd_dmaengine_dai_dma_data *dma_params_fe = NULL;
 	struct snd_dmaengine_dai_dma_data *dma_params_be = NULL;
+	struct dma_chan *tmp_chan = NULL, *tmp_chan_new = NULL;
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct fsl_asrc_pair *pair = runtime->private_data;
 	struct fsl_asrc *asrc = pair->asrc;
@@ -142,7 +143,6 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 	int stream = substream->stream;
 	struct imx_dma_data *tmp_data;
 	struct snd_soc_dpcm *dpcm;
-	struct dma_chan *tmp_chan;
 	struct device *dev_be;
 	u8 dir = tx ? OUT : IN;
 	dma_cap_mask_t mask;
@@ -152,6 +152,7 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 	for_each_dpcm_be(rtd, stream, dpcm) {
 		struct snd_soc_pcm_runtime *be = dpcm->be;
 		struct snd_pcm_substream *substream_be;
+		struct snd_soc_component *component_be;
 		struct snd_soc_dai *dai = asoc_rtd_to_cpu(be, 0);
 
 		if (dpcm->fe != rtd)
@@ -160,6 +161,9 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 		substream_be = snd_soc_dpcm_get_substream(be, stream);
 		dma_params_be = snd_soc_dai_get_dma_data(dai, substream_be);
 		dev_be = dai->dev;
+		component_be = snd_soc_lookup_component_nolocked(dev_be, SND_DMAENGINE_PCM_DRV_NAME);
+		if (component_be)
+			tmp_chan = soc_component_to_pcm(component_be)->chan[substream->stream];
 		break;
 	}
 
@@ -205,10 +209,14 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 	 */
 	if (!asrc->use_edma) {
 		/* Get DMA request of Back-End */
-		tmp_chan = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
+		if (!tmp_chan) {
+			tmp_chan_new = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
+			tmp_chan = tmp_chan_new;
+		}
 		tmp_data = tmp_chan->private;
 		pair->dma_data.dma_request = tmp_data->dma_request;
-		dma_release_channel(tmp_chan);
+		if (tmp_chan_new)
+			dma_release_channel(tmp_chan_new);
 
 		/* Get DMA request of Front-End */
 		tmp_chan = asrc->get_dma_channel(pair, dir);
@@ -220,9 +228,26 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 
 		pair->dma_chan[dir] =
 			dma_request_channel(mask, filter, &pair->dma_data);
+		pair->req_dma_chan_dev_to_dev = true;
 	} else {
-		pair->dma_chan[dir] =
-			asrc->get_dma_channel(pair, dir);
+		/*
+		 * With EDMA, there is two dma channels can be used for p2p,
+		 * one is from ASRC, one is from another peripheral
+		 * (ESAI or SAI). Previously we select the dma channel of ASRC,
+		 * but find an issue for ideal ratio case, there is no control
+		 * for data copy speed, the speed is faster than sample
+		 * frequency.
+		 *
+		 * So we switch to use dma channel of peripheral (ESAI or SAI),
+		 * that copy speed of DMA is controlled by data consumption
+		 * speed in the peripheral FIFO.
+		 */
+		pair->req_dma_chan_dev_to_dev = false;
+		pair->dma_chan[dir] = tmp_chan;
+		if (!pair->dma_chan[dir]) {
+			pair->dma_chan[dir] = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
+			pair->req_dma_chan_dev_to_dev = true;
+		}
 	}
 
 	if (!pair->dma_chan[dir]) {
@@ -261,7 +286,8 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 	ret = dmaengine_slave_config(pair->dma_chan[dir], &config_be);
 	if (ret) {
 		dev_err(dev, "failed to config DMA channel for Back-End\n");
-		dma_release_channel(pair->dma_chan[dir]);
+		if (pair->req_dma_chan_dev_to_dev)
+			dma_release_channel(pair->dma_chan[dir]);
 		return ret;
 	}
 
@@ -273,19 +299,21 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 static int fsl_asrc_dma_hw_free(struct snd_soc_component *component,
 				struct snd_pcm_substream *substream)
 {
+	bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct fsl_asrc_pair *pair = runtime->private_data;
+	u8 dir = tx ? OUT : IN;
 
 	snd_pcm_set_runtime_buffer(substream, NULL);
 
-	if (pair->dma_chan[IN])
-		dma_release_channel(pair->dma_chan[IN]);
+	if (pair->dma_chan[!dir])
+		dma_release_channel(pair->dma_chan[!dir]);
 
-	if (pair->dma_chan[OUT])
-		dma_release_channel(pair->dma_chan[OUT]);
+	if (pair->dma_chan[dir] && pair->req_dma_chan_dev_to_dev)
+		dma_release_channel(pair->dma_chan[dir]);
 
-	pair->dma_chan[IN] = NULL;
-	pair->dma_chan[OUT] = NULL;
+	pair->dma_chan[!dir] = NULL;
+	pair->dma_chan[dir] = NULL;
 
 	return 0;
 }
-- 
2.21.0

Re: [RFC PATCH v2 3/3] ASoC: fsl_asrc_dma: Reuse the dma channel if available in Back-End

[Nicolin Chen]

On Wed, Jun 10, 2020 at 06:05:49PM +0800, Shengjiu Wang wrote:
> The dma channel has been requested by Back-End cpu dai driver already.
> If fsl_asrc_dma requests dma chan with same dma:tx symlink, then
> there will be below warning with SDMA.
> 
> [   48.174236] fsl-esai-dai 2024000.esai: Cannot create DMA dma:tx symlink
> 
> or with EDMA the request operation will fail for EDMA channel
> can only be requested once.
> 
> So If we can reuse the dma channel of Back-End, then the issue can be
> fixed.
> 
> In order to get the dma channel which is already requested in Back-End.
> we use the exported two functions (snd_soc_lookup_component_nolocked
> and soc_component_to_pcm). If we can get the dma channel, then reuse it,
> if can't, then request a new one.
> 
> Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
> ---
>  sound/soc/fsl/fsl_asrc_common.h |  2 ++
>  sound/soc/fsl/fsl_asrc_dma.c    | 52 +++++++++++++++++++++++++--------
>  2 files changed, 42 insertions(+), 12 deletions(-)

> diff --git a/sound/soc/fsl/fsl_asrc_common.h b/sound/soc/fsl/fsl_asrc_common.h
> index 77665b15c8db..09512bc79b80 100644
> --- a/sound/soc/fsl/fsl_asrc_common.h
> +++ b/sound/soc/fsl/fsl_asrc_common.h
> @@ -32,6 +32,7 @@ enum asrc_pair_index {
>   * @dma_chan: inputer and output DMA channels
>   * @dma_data: private dma data
>   * @pos: hardware pointer position
> + * @req_dma_chan_dev_to_dev: flag for release dev_to_dev chan

Since we only have dma_request call for back-end only:
+ * @req_dma_chan: flag to release back-end dma chan

> diff --git a/sound/soc/fsl/fsl_asrc_dma.c b/sound/soc/fsl/fsl_asrc_dma.c
> index d6a3fc5f87e5..5ecb77d466d3 100644
> --- a/sound/soc/fsl/fsl_asrc_dma.c
> +++ b/sound/soc/fsl/fsl_asrc_dma.c
> @@ -160,6 +161,9 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
>  		substream_be = snd_soc_dpcm_get_substream(be, stream);
>  		dma_params_be = snd_soc_dai_get_dma_data(dai, substream_be);
>  		dev_be = dai->dev;
> +		component_be = snd_soc_lookup_component_nolocked(dev_be, SND_DMAENGINE_PCM_DRV_NAME);
> +		if (component_be)
> +			tmp_chan = soc_component_to_pcm(component_be)->chan[substream->stream];

Should we use substream_be->stream or just substream->stream?

And would be better to add these lines right before we really use
tmp_chan because there's still some distance till it reaches that
point. And would be better to have a line of comments too.

> @@ -205,10 +209,14 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
>  	 */
>  	if (!asrc->use_edma) {
>  		/* Get DMA request of Back-End */
> -		tmp_chan = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
> +		if (!tmp_chan) {
> +			tmp_chan_new = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
> +			tmp_chan = tmp_chan_new;

This is a bit confusing...though I finally got it :)
So probably better to have a line of comments.

> @@ -220,9 +228,26 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
>  
>  		pair->dma_chan[dir] =
>  			dma_request_channel(mask, filter, &pair->dma_data);
> +		pair->req_dma_chan_dev_to_dev = true;
>  	} else {
> -		pair->dma_chan[dir] =
> -			asrc->get_dma_channel(pair, dir);
> +		/*
> +		 * With EDMA, there is two dma channels can be used for p2p,
> +		 * one is from ASRC, one is from another peripheral
> +		 * (ESAI or SAI). Previously we select the dma channel of ASRC,
> +		 * but find an issue for ideal ratio case, there is no control
> +		 * for data copy speed, the speed is faster than sample
> +		 * frequency.
> +		 *
> +		 * So we switch to use dma channel of peripheral (ESAI or SAI),
> +		 * that copy speed of DMA is controlled by data consumption
> +		 * speed in the peripheral FIFO.
> +		 */

This sounds like a different issue and should be fixed separately?
If you prefer not to, better to move this one to commit log, other
than having a changelog here, in my opinion.

Since it no longer uses get_dma_channel() for EDMA case, we should
update the comments at the top as well.

> +		pair->req_dma_chan_dev_to_dev = false;
> +		pair->dma_chan[dir] = tmp_chan;
> +		if (!pair->dma_chan[dir]) {
> +			pair->dma_chan[dir] = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
> +			pair->req_dma_chan_dev_to_dev = true;
> +		}
>  	}

Now there are some duplicated lines between these if-else routines, so
combining my previous comments, we can do (sample change, not tested):

@@ -197,18 +199,29 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 	dma_cap_set(DMA_SLAVE, mask);
 	dma_cap_set(DMA_CYCLIC, mask);
 
+	/*
+	 * The Back-End device might have already requested a DMA channel,
+	 * so try to reuse it first, and then request a new one upon NULL.
+	 */
+	component_be = snd_soc_lookup_component_nolocked(dev_be, SND_DMAENGINE_PCM_DRV_NAME);
+	if (component_be)	// should probably error out if !component_be?
+		tmp_chan = be_chan = soc_component_to_pcm(component_be)->chan[substream->stream];
+	if (!tmp_chan)
+		tmp_chan = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
+
 	/*
 	 * An EDMA DEV_TO_DEV channel is fixed and bound with DMA event of each
 	 * peripheral, unlike SDMA channel that is allocated dynamically. So no
-	 * need to configure dma_request and dma_request2, but get dma_chan via
-	 * dma_request_slave_channel directly with dma name of Front-End device
+	 * need to configure dma_request and dma_request2, but get dma_chan of
+	 * Back-End device directly via dma_request_slave_channel.
 	 */
 	if (!asrc->use_edma) {
 		/* Get DMA request of Back-End */
-		tmp_chan = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
 		tmp_data = tmp_chan->private;
 		pair->dma_data.dma_request = tmp_data->dma_request;
-		dma_release_channel(tmp_chan);
+		/* Do not release tmp_chan if we are reusing the Back-End one */
+		if (!be_chan)
+			dma_release_channel(tmp_chan);
 
 		/* Get DMA request of Front-End */
 		tmp_chan = asrc->get_dma_channel(pair, dir);
@@ -220,9 +233,11 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 
 		pair->dma_chan[dir] =
 			dma_request_channel(mask, filter, &pair->dma_data);
+		pair->req_dma_chan = true;
 	} else {
-		pair->dma_chan[dir] =
-			asrc->get_dma_channel(pair, dir);
+		pair->dma_chan[dir] = tmp_chan;
+		/* Do not flag to release if we are reusing the Back-End one */
+		pair->req_dma_chan = !be_chan;
 	}
 
 	if (!pair->dma_chan[dir]) {

> @@ -273,19 +299,21 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
>  static int fsl_asrc_dma_hw_free(struct snd_soc_component *component,
>  				struct snd_pcm_substream *substream)
>  {
> +	bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
>  	struct snd_pcm_runtime *runtime = substream->runtime;
>  	struct fsl_asrc_pair *pair = runtime->private_data;
> +	u8 dir = tx ? OUT : IN;
>  
>  	snd_pcm_set_runtime_buffer(substream, NULL);
>  
> -	if (pair->dma_chan[IN])
> -		dma_release_channel(pair->dma_chan[IN]);
> +	if (pair->dma_chan[!dir])
> +		dma_release_channel(pair->dma_chan[!dir]);
>  
> -	if (pair->dma_chan[OUT])
> -		dma_release_channel(pair->dma_chan[OUT]);
> +	if (pair->dma_chan[dir] && pair->req_dma_chan_dev_to_dev)
> +		dma_release_channel(pair->dma_chan[dir]);

Why we only apply this to one direction?

Re: [RFC PATCH v2 3/3] ASoC: fsl_asrc_dma: Reuse the dma channel if available in Back-End

[Shengjiu Wang]

On Fri, Jun 12, 2020 at 8:33 AM Nicolin Chen <nicoleotsuka@gmail.com> wrote:
>
> On Wed, Jun 10, 2020 at 06:05:49PM +0800, Shengjiu Wang wrote:
> > The dma channel has been requested by Back-End cpu dai driver already.
> > If fsl_asrc_dma requests dma chan with same dma:tx symlink, then
> > there will be below warning with SDMA.
> >
> > [   48.174236] fsl-esai-dai 2024000.esai: Cannot create DMA dma:tx symlink
> >
> > or with EDMA the request operation will fail for EDMA channel
> > can only be requested once.
> >
> > So If we can reuse the dma channel of Back-End, then the issue can be
> > fixed.
> >
> > In order to get the dma channel which is already requested in Back-End.
> > we use the exported two functions (snd_soc_lookup_component_nolocked
> > and soc_component_to_pcm). If we can get the dma channel, then reuse it,
> > if can't, then request a new one.
> >
> > Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
> > ---
> >  sound/soc/fsl/fsl_asrc_common.h |  2 ++
> >  sound/soc/fsl/fsl_asrc_dma.c    | 52 +++++++++++++++++++++++++--------
> >  2 files changed, 42 insertions(+), 12 deletions(-)
>
> > diff --git a/sound/soc/fsl/fsl_asrc_common.h b/sound/soc/fsl/fsl_asrc_common.h
> > index 77665b15c8db..09512bc79b80 100644
> > --- a/sound/soc/fsl/fsl_asrc_common.h
> > +++ b/sound/soc/fsl/fsl_asrc_common.h
> > @@ -32,6 +32,7 @@ enum asrc_pair_index {
> >   * @dma_chan: inputer and output DMA channels
> >   * @dma_data: private dma data
> >   * @pos: hardware pointer position
> > + * @req_dma_chan_dev_to_dev: flag for release dev_to_dev chan
>
> Since we only have dma_request call for back-end only:
> + * @req_dma_chan: flag to release back-end dma chan

I prefer to use the description "flag to release dev_to_dev chan"
because we won't release the dma chan of the back-end. if the chan
is from the back-end, it is owned by the back-end component.

>
> > diff --git a/sound/soc/fsl/fsl_asrc_dma.c b/sound/soc/fsl/fsl_asrc_dma.c
> > index d6a3fc5f87e5..5ecb77d466d3 100644
> > --- a/sound/soc/fsl/fsl_asrc_dma.c
> > +++ b/sound/soc/fsl/fsl_asrc_dma.c
> > @@ -160,6 +161,9 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
> >               substream_be = snd_soc_dpcm_get_substream(be, stream);
> >               dma_params_be = snd_soc_dai_get_dma_data(dai, substream_be);
> >               dev_be = dai->dev;
> > +             component_be = snd_soc_lookup_component_nolocked(dev_be, SND_DMAENGINE_PCM_DRV_NAME);
> > +             if (component_be)
> > +                     tmp_chan = soc_component_to_pcm(component_be)->chan[substream->stream];
>
> Should we use substream_be->stream or just substream->stream?

substream_be->stream should be better.

>
> And would be better to add these lines right before we really use
> tmp_chan because there's still some distance till it reaches that
> point. And would be better to have a line of comments too.

ok.

>
> > @@ -205,10 +209,14 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
> >        */
> >       if (!asrc->use_edma) {
> >               /* Get DMA request of Back-End */
> > -             tmp_chan = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
> > +             if (!tmp_chan) {
> > +                     tmp_chan_new = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
> > +                     tmp_chan = tmp_chan_new;
>
> This is a bit confusing...though I finally got it :)
> So probably better to have a line of comments.

ok.

>
> > @@ -220,9 +228,26 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
> >
> >               pair->dma_chan[dir] =
> >                       dma_request_channel(mask, filter, &pair->dma_data);
> > +             pair->req_dma_chan_dev_to_dev = true;
> >       } else {
> > -             pair->dma_chan[dir] =
> > -                     asrc->get_dma_channel(pair, dir);
> > +             /*
> > +              * With EDMA, there is two dma channels can be used for p2p,
> > +              * one is from ASRC, one is from another peripheral
> > +              * (ESAI or SAI). Previously we select the dma channel of ASRC,
> > +              * but find an issue for ideal ratio case, there is no control
> > +              * for data copy speed, the speed is faster than sample
> > +              * frequency.
> > +              *
> > +              * So we switch to use dma channel of peripheral (ESAI or SAI),
> > +              * that copy speed of DMA is controlled by data consumption
> > +              * speed in the peripheral FIFO.
> > +              */
>
> This sounds like a different issue and should be fixed separately?
> If you prefer not to, better to move this one to commit log, other
> than having a changelog here, in my opinion.

ok, will move it in commit log.

>
> Since it no longer uses get_dma_channel() for EDMA case, we should
> update the comments at the top as well.
>
> > +             pair->req_dma_chan_dev_to_dev = false;
> > +             pair->dma_chan[dir] = tmp_chan;
> > +             if (!pair->dma_chan[dir]) {
> > +                     pair->dma_chan[dir] = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
> > +                     pair->req_dma_chan_dev_to_dev = true;
> > +             }
> >       }
>
> Now there are some duplicated lines between these if-else routines, so
> combining my previous comments, we can do (sample change, not tested):

ok, will try yours.

>
> @@ -197,18 +199,29 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
>         dma_cap_set(DMA_SLAVE, mask);
>         dma_cap_set(DMA_CYCLIC, mask);
>
> +       /*
> +        * The Back-End device might have already requested a DMA channel,
> +        * so try to reuse it first, and then request a new one upon NULL.
> +        */
> +       component_be = snd_soc_lookup_component_nolocked(dev_be, SND_DMAENGINE_PCM_DRV_NAME);
> +       if (component_be)       // should probably error out if !component_be?
> +               tmp_chan = be_chan = soc_component_to_pcm(component_be)->chan[substream->stream];
> +       if (!tmp_chan)
> +               tmp_chan = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
> +
>         /*
>          * An EDMA DEV_TO_DEV channel is fixed and bound with DMA event of each
>          * peripheral, unlike SDMA channel that is allocated dynamically. So no
> -        * need to configure dma_request and dma_request2, but get dma_chan via
> -        * dma_request_slave_channel directly with dma name of Front-End device
> +        * need to configure dma_request and dma_request2, but get dma_chan of
> +        * Back-End device directly via dma_request_slave_channel.
>          */
>         if (!asrc->use_edma) {
>                 /* Get DMA request of Back-End */
> -               tmp_chan = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
>                 tmp_data = tmp_chan->private;
>                 pair->dma_data.dma_request = tmp_data->dma_request;
> -               dma_release_channel(tmp_chan);
> +               /* Do not release tmp_chan if we are reusing the Back-End one */
> +               if (!be_chan)
> +                       dma_release_channel(tmp_chan);
>
>                 /* Get DMA request of Front-End */
>                 tmp_chan = asrc->get_dma_channel(pair, dir);
> @@ -220,9 +233,11 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
>
>                 pair->dma_chan[dir] =
>                         dma_request_channel(mask, filter, &pair->dma_data);
> +               pair->req_dma_chan = true;
>         } else {
> -               pair->dma_chan[dir] =
> -                       asrc->get_dma_channel(pair, dir);
> +               pair->dma_chan[dir] = tmp_chan;
> +               /* Do not flag to release if we are reusing the Back-End one */
> +               pair->req_dma_chan = !be_chan;
>         }
>
>         if (!pair->dma_chan[dir]) {
>
> > @@ -273,19 +299,21 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
> >  static int fsl_asrc_dma_hw_free(struct snd_soc_component *component,
> >                               struct snd_pcm_substream *substream)
> >  {
> > +     bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
> >       struct snd_pcm_runtime *runtime = substream->runtime;
> >       struct fsl_asrc_pair *pair = runtime->private_data;
> > +     u8 dir = tx ? OUT : IN;
> >
> >       snd_pcm_set_runtime_buffer(substream, NULL);
> >
> > -     if (pair->dma_chan[IN])
> > -             dma_release_channel(pair->dma_chan[IN]);
> > +     if (pair->dma_chan[!dir])
> > +             dma_release_channel(pair->dma_chan[!dir]);
> >
> > -     if (pair->dma_chan[OUT])
> > -             dma_release_channel(pair->dma_chan[OUT]);
> > +     if (pair->dma_chan[dir] && pair->req_dma_chan_dev_to_dev)
> > +             dma_release_channel(pair->dma_chan[dir]);
>
> Why we only apply this to one direction?

if the chan is from the back-end, it is owned by the back-end
component, so it should be released by the back-end component,
not here. That's why I added the flag "req_dma_chan".

Re: [RFC PATCH v2 3/3] ASoC: fsl_asrc_dma: Reuse the dma channel if available in Back-End

[Nicolin Chen]

On Fri, Jun 12, 2020 at 10:17:08AM +0800, Shengjiu Wang wrote:

> > > diff --git a/sound/soc/fsl/fsl_asrc_common.h b/sound/soc/fsl/fsl_asrc_common.h

> > > + * @req_dma_chan_dev_to_dev: flag for release dev_to_dev chan
> >
> > Since we only have dma_request call for back-end only:
> > + * @req_dma_chan: flag to release back-end dma chan
> 
> I prefer to use the description "flag to release dev_to_dev chan"
> because we won't release the dma chan of the back-end. if the chan
> is from the back-end, it is owned by the back-end component.

TBH, it just looks too long. But I wouldn't have problem if you
insist so.

> > > @@ -273,19 +299,21 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
> > >  static int fsl_asrc_dma_hw_free(struct snd_soc_component *component,
> > >                               struct snd_pcm_substream *substream)
> > >  {
> > > +     bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
> > >       struct snd_pcm_runtime *runtime = substream->runtime;
> > >       struct fsl_asrc_pair *pair = runtime->private_data;
> > > +     u8 dir = tx ? OUT : IN;
> > >
> > >       snd_pcm_set_runtime_buffer(substream, NULL);
> > >
> > > -     if (pair->dma_chan[IN])
> > > -             dma_release_channel(pair->dma_chan[IN]);
> > > +     if (pair->dma_chan[!dir])
> > > +             dma_release_channel(pair->dma_chan[!dir]);
> > >
> > > -     if (pair->dma_chan[OUT])
> > > -             dma_release_channel(pair->dma_chan[OUT]);
> > > +     if (pair->dma_chan[dir] && pair->req_dma_chan_dev_to_dev)
> > > +             dma_release_channel(pair->dma_chan[dir]);
> >
> > Why we only apply this to one direction?
> 
> if the chan is from the back-end, it is owned by the back-end
> component, so it should be released by the back-end component,
> not here. That's why I added the flag "req_dma_chan".

Ah...I forgot the IN and OUT is for front-end and back-end. The
naming isn't very good indeed. Probably we should add a line of
comments somewhere as a reminder.

Thanks