linux-kernel - Re: [PATCH v3 2/2] ASoC: Intel: Add period size constraint on strago board

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Date:   Tue, 4 Aug 2020 09:24:49 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     "Lu, Brent" <brent.lu@...el.com>, Takashi Iwai <tiwai@...e.de>
Cc:     Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "yuhsuan@...gle.com" <yuhsuan@...gle.com>,
        Takashi Iwai <tiwai@...e.com>,
        Jie Yang <yang.jie@...ux.intel.com>,
        "Rojewski, Cezary" <cezary.rojewski@...el.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Sam McNally <sammc@...omium.org>,
        Mark Brown <broonie@...nel.org>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Daniel Stuart <daniel.stuart14@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Yu-Hsuan Hsu <yuhsuan@...omium.org>,
        Damian van Soelen <dj.vsoelen@...il.com>
Subject: Re: [PATCH v3 2/2] ASoC: Intel: Add period size constraint on strago
 board



On 8/3/20 11:33 PM, Lu, Brent wrote:
>>
>> For avoid further misunderstanding: it's fine that CRAS *uses* such a short
>> period.  It's often required for achieving a short latency.
>>
>> However, the question is whether the driver can set *only* this value for
>> making it working.  IOW, if we don't have this constraint, what actually
>> happens?  If the driver gives the period size alignment, wouldn't CRAS
>> choose 240?
> 
> It won't. Without the constraint it becomes 432. Actually CRAS does not set
> period size specifically so the value depends on the constraint rules.

I don't get this. If the platform driver already stated 240 and 960 
samples why would 432 be chosen? Doesn't this mean the constraint is not 
applied?

> [   52.011146] sound pcmC1D0p: hw_param
> [   52.011152] sound pcmC1D0p:   ACCESS 0x1
> [   52.011155] sound pcmC1D0p:   FORMAT 0x4
> [   52.011158] sound pcmC1D0p:   SUBFORMAT 0x1
> [   52.011161] sound pcmC1D0p:   SAMPLE_BITS [16:16]
> [   52.011164] sound pcmC1D0p:   FRAME_BITS [32:32]
> [   52.011167] sound pcmC1D0p:   CHANNELS [2:2]
> [   52.011170] sound pcmC1D0p:   RATE [48000:48000]
> [   52.011173] sound pcmC1D0p:   PERIOD_TIME [9000:9000]
> [   52.011176] sound pcmC1D0p:   PERIOD_SIZE [432:432]
> [   52.011179] sound pcmC1D0p:   PERIOD_BYTES [1728:1728]
> [   52.011182] sound pcmC1D0p:   PERIODS [474:474]
> [   52.011185] sound pcmC1D0p:   BUFFER_TIME [4266000:4266000]
> [   52.011188] sound pcmC1D0p:   BUFFER_SIZE [204768:204768]
> [   52.011191] sound pcmC1D0p:   BUFFER_BYTES [819072:819072]
> [   52.011194] sound pcmC1D0p:   TICK_TIME [0:0]
> 
> Regards,
> Brent
> 
>>
>>
>> Takashi
> 
>