linux-kernel - Re: [alsa-devel] [PATCH] ASoC: dpcm: don't do hw_param when BE has done hw_param

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Date:	Fri, 10 Jan 2014 19:59:42 +0800
From:	Nenghua Cao <nhcao@...vell.com>
To:	Liam Girdwood <liam.r.girdwood@...ux.intel.com>
CC:	Takashi Iwai <tiwai@...e.de>, Mark Brown <broonie@...nel.org>,
	Jaroslav Kysela <perex@...ex.cz>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [alsa-devel] [PATCH] ASoC: dpcm: don't do hw_param when BE has
 done	hw_param

On 01/10/2014 07:47 PM, Liam Girdwood wrote:
> On Fri, 2014-01-10 at 19:21 +0800, Nenghua Cao wrote:
>> On 01/10/2014 06:55 PM, Takashi Iwai wrote:
>>> [Corrected mail addresses of both Mark and Liam]
>>>
>> Hi, Takashi:
>> Thanks for correcting my mistake.
>>> At Fri, 10 Jan 2014 13:36:35 +0800,
>>> Nenghua Cao wrote:
>>>>
>>>> From: Nenghua Cao <nhcao@...vell.com>
>>>>
>>>>     It fixes the following case:
>>>>     Two FEs connects the same BE; FE1 & BE path has been opened and hw_paramed.
>>>> At this momment, FE2 & BE path is being opened and hw_paramed. The BE
>>>> dai will do hw_param again even if it has done hw_param. It is not
>>>> reasonable.
>>>> FE1------------>BE
>>>> FE2-------------^
>>>
>>> What happens if FE2 tries to set up an incompatible hw_params?
>>> (Through a quick glance, it won't work properly well, too, though...)
>>>
> 
> The intention in this case would be for the DSP FE driver to determine
> if it can perform format conversion or SRC to the running BE. If the DSP
> cant do the conversion then it should fail.
> 
>> If FE2 uses an incompatible param, it will make FE1 doesn't work. Maybe
>> FE2 works well.
>> If FE2 uses the same param, BE hw_param function will be called twice
>> (This is the most happening case).
>> So we can't get benefits from it.
> 
> We shouldn't be calling the hw_params() on the BE when it's already
> configured in this case. So this seems like a bug. However :-
> 
> /* only allow hw_params() if no connected FEs are running */
> 		if (!snd_soc_dpcm_can_be_params(fe, be, stream))
> 			continue;
> 
> 		if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_OPEN) &&
> 		    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_HW_PARAMS) &&
> 		    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_HW_FREE))
> 			continue;
> 
> We do do a test to check if any connected FEs are running (i.e.
> triggered) prior to calling hw_params() on the BE. Can you confirm if
> the FE was running in your case ?
> 
Hi, Liam:
   I am so glad to hear from you. In my case, FE1 has called hw_param,
and before FE1 calls prepare/trigger function, the scheduler switches to
do FE2 open, hw_param. So hw_param is called twice.

> Thanks
> 
> Liam
> 
>>>
>>> Takashi
>>>
>>>>
>>>> Signed-off-by: Nenghua Cao <nhcao@...vell.com>
>>>> ---
>>>>  sound/soc/soc-pcm.c |    1 -
>>>>  1 files changed, 0 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
>>>> index 891b9a9..ec07e37 100644
>>>> --- a/sound/soc/soc-pcm.c
>>>> +++ b/sound/soc/soc-pcm.c
>>>> @@ -1339,7 +1339,6 @@ static int dpcm_be_dai_hw_params(struct snd_soc_pcm_runtime *fe, int stream)
>>>>  			continue;
>>>>  
>>>>  		if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_OPEN) &&
>>>> -		    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_HW_PARAMS) &&
>>>>  		    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_HW_FREE))
>>>>  			continue;
>>>>  
>>>> -- 
>>>> 1.7.0.4
>>>>
>>>> _______________________________________________
>>>> Alsa-devel mailing list
>>>> Alsa-devel@...a-project.org
>>>> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
>>>>
>>
> 
> 
> 

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