Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   09 Sep 2019 12:54:45 +0900
Message-ID: <87mufe5dkq.wl-kuninori.morimoto.gx@renesas.com>
From:   Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
To:     Katsuhiro Suzuki <katsuhiro@katsuster.net>
Cc:     Mark Brown <broonie@kernel.org>, alsa-devel@alsa-project.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] SoC: simple-card-utils: set 0Hz to sysclk when shutdown
In-Reply-To: <af9678aa-bd38-7cb5-5d25-b133a269f19f@katsuster.net>
References: <20190907174501.19833-1-katsuhiro@katsuster.net>
        <87woei5mzj.wl-kuninori.morimoto.gx@renesas.com>
        <af9678aa-bd38-7cb5-5d25-b133a269f19f@katsuster.net>
User-Agent: Wanderlust/2.15.9 Emacs/24.5 Mule/6.0
MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue")
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


Hi Katsuhiro

> >> Bad scenario as follows (mclk-fs = 256):
> >>     - Initialize sysclk by correct value (Ex. 12.288MHz)
> >>       - Codec set constraints of PCM rate by sysclk
> >>         48kHz (1/256), 32kHz (1/384), 24kHz (1/512)
> >>     - Play 48kHz sound, it's acceptable
> >>     - Sysclk is not changed
> >> 
> >>     - Play 32kHz sound, it's acceptable
> >>     - Set sysclk to 8.192MHz (= fs * mclk-fs = 32k * 256)
> >>       - Codec set constraints of PCM rate by sysclk
> >>         32kHz (1/256), 21.33kHz (1/384), 16kHz (1/512)
> >> 
> >>     - Play 48kHz again, but it's NOT acceptable because constraints
> >>       do not allow 48kHz
(snip)
> Ah, sorry for confusing. It's not either. hw_params() of machine
> driver has been called even if constraints don't have a requested
> PCM rate. But it's not expected.
> 
> For example, if constraints are 32k, 21.33k, 16k, hw_params() will
> be called with 32k when an user requests to play 48k sounds.

Oh, I see.
Thank you for explaining.

Thank you for your help !!
Best regards
---
Kuninori Morimoto