linux-kernel - Re: [alsa-devel] [PATCH] ASoC: soc-pcm: Use delay set in pointer function

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Message-ID: <e0990b62-897c-6dc7-8ac9-296932c505b7@amd.com>
Date:   Sat, 28 Jul 2018 09:58:00 +0530
From:   "Agrawal, Akshu" <Akshu.Agrawal@....com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     "moderated list:SOUND - SOC LAYER / DYNAMIC AUDIO POWER MANAGEM..." 
        <alsa-devel@...a-project.org>,
        open list <linux-kernel@...r.kernel.org>,
        Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>, djkurtz@...omium.org,
        Mark Brown <broonie@...nel.org>, Alexander.Deucher@....com
Subject: Re: [alsa-devel] [PATCH] ASoC: soc-pcm: Use delay set in pointer
 function



On 7/27/2018 8:39 PM, Pierre-Louis Bossart wrote:
> On 7/27/18 5:13 AM, Akshu Agrawal wrote:
>> There are cases where a pointer function populates
>> runtime->delay, such as:
>> ./sound/pci/hda/hda_controller.c
>> ./sound/soc/intel/atom/sst-mfld-platform-pcm.c
>>
>> Also, in some cases cpu dai used is generic and the pcm
>> driver needs to set delay.
>>
>> This delay was getting lost and was overwritten by delays
>> from codec or cpu dai delay function if exposed.
> 
> Humm, yes the runtime->delay set in the .pointer function would be lost 
> without this change, but the delay would still be provided in the 
> followup call to .delay.
> With your change, the same delay will be accounted for twice?
> 

It will not be accounted twice because no driver which is setting
runtime->delay is defining .delay op for cpu_dai. Vice versa is also
true, the drivers which define .delay for cpu_dai don't set
runtime->delay. And I think this is expected from drivers else it would
be a bug from their side.

.delay for codec_dai anyway is different and has to be accounted for.

Thanks,
Akshu
>>
>> Signed-off-by: Akshu Agrawal <akshu.agrawal@....com>
>> ---
>>   sound/soc/soc-pcm.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
>> index 98be04b..b1a2bc2 100644
>> --- a/sound/soc/soc-pcm.c
>> +++ b/sound/soc/soc-pcm.c
>> @@ -1179,6 +1179,9 @@ static snd_pcm_uframes_t soc_pcm_pointer(struct snd_pcm_substream *substream)
>>   	snd_pcm_sframes_t codec_delay = 0;
>>   	int i;
>>   
>> +	/* clearing the previous delay */
>> +	runtime->delay = 0;
>> +
>>   	for_each_rtdcom(rtd, rtdcom) {
>>   		component = rtdcom->component;
>>   
>> @@ -1203,7 +1206,7 @@ static snd_pcm_uframes_t soc_pcm_pointer(struct snd_pcm_substream *substream)
>>   	}
>>   	delay += codec_delay;
>>   
>> -	runtime->delay = delay;
>> +	runtime->delay += delay;
>>   
>>   	return offset;
>>   }
>>
>