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

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Date:   Thu, 30 Jul 2020 18:56:03 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     "Lu, Brent" <brent.lu@...el.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com>,
        "Rojewski, Cezary" <cezary.rojewski@...el.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        Jie Yang <yang.jie@...ux.intel.com>,
        Takashi Iwai <tiwai@...e.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        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 2/2] ASoC: Intel: Add period size constraint on strago board

On Thu, 30 Jul 2020 17:27:58 +0200,
Pierre-Louis Bossart wrote:
> 
> 
> 
> >> Is this patch required if you've already constrained the period sizes for the
> >> platform driver in patch1?
> >
> > Yes or alsa will select 320 as default period size for it.
> 
> ok, then that's a miss in your patch1. 320 samples is a multiple of
> 1ms for 48kHz rates. I think it was valid only for the 16kHz VoIP
> paths used in some versions of Android, but that we don't support in
> the upstream code.
> 
> To build on Takashi's answer, the real ask here is to require that the
> period be a multiple of 1ms, because that's the fundamental
> design/limitation of firmware. It doesn't matter if it's 48, 96, 192,
> 240, 480, 960 samples.

If the 1ms alignment is the condition, it can be better with a
different hw_params constraint.  We can use
snd_pcm_hw_constraint_step() for such a purpose.


thanks,

Takashi