[RFC PATCH v2 3/3] ASoC: fsl_asrc_dma: Reuse the dma channel if available in Back-End
Shengjiu Wang
shengjiu.wang at gmail.com
Fri Jun 12 04:17:08 CEST 2020
On Fri, Jun 12, 2020 at 8:33 AM Nicolin Chen <nicoleotsuka at 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 at 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".
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