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Date: Thu, 11 Jun 2020 17:31:04 -0700
From: Nicolin Chen <nicoleotsuka@...il.com>
To: Shengjiu Wang <shengjiu.wang@....com>
Cc: lars@...afoo.de, perex@...ex.cz, tiwai@...e.com,
lgirdwood@...il.com, broonie@...nel.org, timur@...nel.org,
Xiubo.Lee@...il.com, festevam@...il.com,
alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org
Subject: Re: [RFC PATCH v2 3/3] ASoC: fsl_asrc_dma: Reuse the dma channel if
available in Back-End
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@....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?
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