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 04:33:31 +0000
From:   "Lu, Brent" <brent.lu@...el.com>
To:     Takashi Iwai <tiwai@...e.de>
CC:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        "Guennadi Liakhovetski" <guennadi.liakhovetski@...ux.intel.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "Kuninori Morimoto" <kuninori.morimoto.gx@...esas.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        "Rojewski, Cezary" <cezary.rojewski@...el.com>,
        Jie Yang <yang.jie@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Takashi Iwai <tiwai@...e.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>,
        "yuhsuan@...gle.com" <yuhsuan@...gle.com>
Subject: RE: [PATCH v3 2/2] ASoC: Intel: Add period size constraint on strago
 board

> 
> 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.

[   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