[PATCH 1/4] ASoC: soc-pcm: dpcm: fix playback/capture checks

[Pierre-Louis Bossart]

On 6/16/20 4:02 AM, Stephan Gerhold wrote:
> On Tue, Jun 16, 2020 at 10:54:17AM +0200, Stephan Gerhold wrote:
>> Hi Pierre,
>>
>> On Mon, Jun 08, 2020 at 02:44:12PM -0500, Pierre-Louis Bossart wrote:
>>> Recent changes in the ASoC core prevent multi-cpu BE dailinks from
>>> being used. DPCM does support multi-cpu DAIs for BE Dailinks, but not
>>> for FE.
>>
>> First I want to apologize for introducing this regression.
>> Actually when I made the "Only allow playback/capture if supported"
>> patch I did not realize it would also be used for BE DAIs. :)

No need to apologize, it helped identify configuration issues none of us 
identified. That's progress for me.

>>> Handle the FE checks first, and make sure all DAIs support the same
>>> capabilities within the same dailink.
>>>
>>> BugLink: https://github.com/thesofproject/linux/issues/2031
>>> Fixes: 9b5db059366ae2 ("ASoC: soc-pcm: dpcm: Only allow playback/capture if supported")
>>> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
>>> Reviewed-by: Bard Liao <yung-chuan.liao at linux.intel.com>
>>> Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski at linux.intel.com>
>>> Reviewed-by: Ranjani Sridharan <ranjani.sridharan at linux.intel.com>
>>> Reviewed-by: Daniel Baluta <daniel.baluta at gmail.com>
>>> ---
>>>   sound/soc/soc-pcm.c | 44 ++++++++++++++++++++++++++++++++++----------
>>>   1 file changed, 34 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
>>> index 276505fb9d50..2c114b4542ce 100644
>>> --- a/sound/soc/soc-pcm.c
>>> +++ b/sound/soc/soc-pcm.c
>>> @@ -2789,20 +2789,44 @@ int soc_new_pcm(struct snd_soc_pcm_runtime *rtd, int num)
>>>   	struct snd_pcm *pcm;
>>>   	char new_name[64];
>>>   	int ret = 0, playback = 0, capture = 0;
>>> +	int stream;
>>>   	int i;
>>>   
>>> +	if (rtd->dai_link->dynamic && rtd->num_cpus > 1) {
>>> +		dev_err(rtd->dev,
>>> +			"DPCM doesn't support Multi CPU for Front-Ends yet\n");
>>> +		return -EINVAL;
>>> +	}
>>> +
>>>   	if (rtd->dai_link->dynamic || rtd->dai_link->no_pcm) {
>>> -		cpu_dai = asoc_rtd_to_cpu(rtd, 0);
>>> -		if (rtd->num_cpus > 1) {
>>> -			dev_err(rtd->dev,
>>> -				"DPCM doesn't support Multi CPU yet\n");
>>> -			return -EINVAL;
>>> +		if (rtd->dai_link->dpcm_playback) {
>>> +			stream = SNDRV_PCM_STREAM_PLAYBACK;
>>> +
>>> +			for_each_rtd_cpu_dais(rtd, i, cpu_dai)
>>> +				if (!snd_soc_dai_stream_valid(cpu_dai,
>>> +							      stream)) {
>>> +					dev_err(rtd->card->dev,
>>> +						"CPU DAI %s for rtd %s does not support playback\n",
>>> +						cpu_dai->name,
>>> +						rtd->dai_link->stream_name);
>>> +					return -EINVAL;
>>
>> Unfortunately the "return -EINVAL" here and below break the case where
>> dpcm_playback/dpcm_capture does not exactly match the capabilities of
>> the referenced CPU DAIs. To quote from my commit message:
>>
>>      At the moment, PCM devices for DPCM are only created based on the
>>      dpcm_playback/capture parameters of the DAI link, without considering
>>      if the CPU/FE DAI is actually capable of playback/capture.
>>
>>      Normally the dpcm_playback/capture parameter should match the
>>      capabilities of the CPU DAI. However, there is no way to set that
>>      parameter from the device tree (e.g. with simple-audio-card or
>>      qcom sound cards). dpcm_playback/capture are always both set to 1.
>>
>> The basic idea for my commit was to basically stop using
>> dpcm_playback/capture for the device tree case and infer the
>> capabilities solely based on referenced DAIs. The DAIs expose if they
>> are capable of playback/capture, so I see no reason to be required to
>> duplicate that into the DAI link setup (unless you want to specifically
>> restrict a DAI link to one direction for some reason...)
>>
>> With your patch probe now fails with:
>>
>>     7702000.sound: CPU DAI MultiMedia1 for rtd MultiMedia1 does not support capture
>>
>> because sound/soc/qcom/common.c sets dpcm_playback = dpcm_capture = 1
>> even though that FE DAI is currently configured to be playback-only.
>>
>> I believe Srinivas fixed that problem for the BE DAIs in
>> commit a2120089251f ("ASoC: qcom: common: set correct directions for dailinks")
>> (https://lore.kernel.org/alsa-devel/20200612123711.29130-2-srinivas.kandagatla@linaro.org/)
>>
>> For the QCOM case it may be feasible to set dpcm_playback/dpcm_capture
>> appropriately because it is basically only used with one particular
>> DAI driver. But simple-audio-card is generic and used with many
>> different drivers so hard-coding a call into some other driver like
>> Srinivas did above won't work in that case.

Doesn't simple-card rely on DT blobs that can also be updated?

>> I wonder if we should downgrade your dev_err(...) to a dev_dbg(...),
>> and then simply avoid setting playback/capture = 0.
> 
> Hmm, I wanted to write "avoid setting playback/capture = 1" here
> of course. If dpcm_playback/capture is set but not actually supported
> don't error out but just ignore it. That would essentially make
> dpcm_playback/capture just a restriction of the CPU DAI capabilities.
> 
> Not sure if there is even a usecase for such a restriction,
> maybe dpcm_playback/capture could even be removed entirely...

I'd rather keep the error and fix those bad configurations, and in a 
second step unify dpcm_capture/dpcm_playback/playback_only/capture_only. 
We have too many flags to identify directions and when given too many 
choices it's likely we are going to have corner cases for a while.