linux-kernel - Re: [PATCH 3/4] ASoC: codecs: wsa883x: mute/unmute PA in correct sequence

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Date:   Thu, 23 Mar 2023 13:11:11 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Mark Brown <broonie@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     tiwai@...e.com, lgirdwood@...il.com, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org, johan+linaro@...nel.org,
        steev@...i.org, dmitry.baryshkov@...aro.org
Subject: Re: [PATCH 3/4] ASoC: codecs: wsa883x: mute/unmute PA in correct
 sequence


>> +static int wsa883x_trigger(struct snd_pcm_substream *s, int cmd,
>> +			   struct snd_soc_dai *dai)
>> +{
>> +	switch (cmd) {
>> +	case SNDRV_PCM_TRIGGER_START:
>> +	case SNDRV_PCM_TRIGGER_RESUME:
>> +	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
>> +		wsa883x_digital_mute(dai, false, 0);
>> +		break;
> 
>>  static const struct snd_soc_dai_ops wsa883x_dai_ops = {
>> +	.startup = wsa883x_startup,
>>  	.hw_params = wsa883x_hw_params,
>>  	.hw_free = wsa883x_hw_free,
>> -	.mute_stream = wsa883x_digital_mute,
>> +	.trigger = wsa883x_trigger,
> 
> The trigger is run in atomic context, can you really write safely to a
> SoundWire device there?

Mark, I've seen that comment from you several times, and I wonder if I
am missing something: the triggers for SoundWire managers and dailinks
are typically nonatomic - at least for the Cadence-based solution the
trigger is based on a bank switch that may happen with a delay and with
a wait_for_completion(). Sending a command over the SoundWire channel is
also typically not atomic, there's usually a wait_for_completion() as well.