linux-kernel - Re: [PATCH] sound: soc: fsl: Do not set DAI sysclk when it is equal to system freq

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Date:   Tue, 5 Sep 2017 16:15:50 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Łukasz Majewski <lukma@...x.de>
Cc:     Nicolin Chen <nicoleotsuka@...il.com>, Timur Tabi <timur@...i.org>,
        Xiubo Li <Xiubo.Lee@...il.com>,
        Fabio Estevam <fabio.estevam@....com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sound: soc: fsl: Do not set DAI sysclk when it is equal
 to system freq

On Tue, Sep 05, 2017 at 10:19:05AM +0200, Łukasz Majewski wrote:
> On 09/05/2017 09:52 AM, Nicolin Chen wrote:

> > Can you elaborate why you set ipg clock as bclk? I don't remember SSI could
> > derive bitclock from ipg clock.

> Just to be clear:

> What clock shall be set with:

> struct snd_soc_dai_ops {
> 	int (*set_sysclk)(struct snd_soc_dai *dai,
> 		int clk_id, unsigned int freq, int dir);
> }

> callback?

> The SSI IP block or BCLK ?

Not the BCLK, probably the IP clock but perhaps nothing.  The bclk is
usually derived from the sample rate and width, the system clock is the
clock rate going into the device.  It doesn't *have* to be configured
(particuarly if it's discoverable by the IP and managable via the clock
API).

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