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

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Message-ID: <dd4d3dc6-88f3-d53f-cd5c-5035c80be3da@linux.intel.com>
Date:   Mon, 30 Jul 2018 10:15:44 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     "Agrawal, Akshu" <Akshu.Agrawal@....com>
Cc:     "moderated list:SOUND - SOC LAYER / DYNAMIC AUDIO POWER MANAGEM..." 
        <alsa-devel@...a-project.org>, Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>, djkurtz@...omium.org,
        open list <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>, Alexander.Deucher@....com
Subject: Re: [alsa-devel] [PATCH] ASoC: soc-pcm: Use delay set in pointer
 function

On 7/27/18 11:28 PM, Agrawal, Akshu wrote:
> 
> 
> 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.

what do you mean my 'no driver'? Can you clarify if this is based on 
analysis of the code or by-design. I don't recall having seen any 
guidelines on this topic, and it's quite likely that different people 
have different interpretation on how delay is supposed to be reported.

> 
> .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;
>>>    }
>>>
>>
> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@...a-project.org
> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
> 

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