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

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Message-ID: <CAOMZO5Bifb8VcOLTd5dEY9KvnvY1jwVr4R4DVRT65Yzm7n6dpA@mail.gmail.com>
Date:   Sun, 3 Sep 2017 12:29:53 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Łukasz Majewski <lukma@...x.de>
Cc:     Fabio Estevam <fabio.estevam@....com>, Timur Tabi <timur@...i.org>,
        Nicolin Chen <nicoleotsuka@...il.com>,
        Xiubo Li <Xiubo.Lee@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.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 Sun, Sep 3, 2017 at 11:40 AM, Łukasz Majewski <lukma@...x.de> wrote:

> This is the part of fsl_ssi_set_bclk() function which is called after
> fsl_ssi_set_dai_sysclk() (which sets ssi_private->bitclk_freq = freq;).
>
> Before the aforementioned check we do have:
>
>         if (ssi_private->bitclk_freq)
>                 freq = ssi_private->bitclk_freq;
>         else
>                 freq = params_channels(hw_params) * 32 *
> params_rate(hw_params);
>
>
> Which assigns freq = bitclk_freq (66 MHz)
>
> And then we break on this particular check:
>
> 66MHz * 5 > 66 MHz.
>
>
>
> The culprit IMHO is the  ssi_private->bitclk_freq = freq; in the
> fsl_ssi_set_dai_sysclk(), since we _should_ set SSI's IP block clock
> (ssi_private->clk), not the bit clock (BCLK).
>
>
> This patch just quits early if it detects change, which don't need to be
> done.

Thanks for the clarification.

Reviewed-by: Fabio Estevam <fabio.estevam@....com>