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Date:   Thu, 30 Jul 2020 18:56:03 +0200
Message-ID: <s5hy2n1aqn0.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc:     "Lu, Brent" <brent.lu@intel.com>,
        "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
        Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>,
        "Rojewski, Cezary" <cezary.rojewski@intel.com>,
        Kai Vehmanen <kai.vehmanen@linux.intel.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>,
        Jie Yang <yang.jie@linux.intel.com>,
        Takashi Iwai <tiwai@suse.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Liam Girdwood <liam.r.girdwood@linux.intel.com>,
        Sam McNally <sammc@chromium.org>,
        Mark Brown <broonie@kernel.org>,
        Ranjani Sridharan <ranjani.sridharan@linux.intel.com>,
        Daniel Stuart <daniel.stuart14@gmail.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Yu-Hsuan Hsu <yuhsuan@chromium.org>,
        Damian van Soelen <dj.vsoelen@gmail.com>
Subject: Re: [PATCH 2/2] ASoC: Intel: Add period size constraint on strago board
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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