linux-kernel - Re: [PATCH v3] ASoC: amd: add support for rt5682 codec in machine driver

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Date:   Tue, 16 Mar 2021 09:53:56 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     "Mukunda,Vijendar" <vijendar.mukunda@....com>, broonie@...nel.org,
        alsa-devel@...a-project.org
Cc:     Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        Arnd Bergmann <arnd@...db.de>,
        Liam Girdwood <lgirdwood@...il.com>,
        open list <linux-kernel@...r.kernel.org>,
        Chuhong Yuan <hslester96@...il.com>,
        Takashi Iwai <tiwai@...e.com>,
        Ravulapati Vishnu vardhan rao 
        <Vishnuvardhanrao.Ravulapati@....com>, Alexander.Deucher@....com,
        Virendra-Pratap.Arya@....com, Murali-krishna.Vemuri@....com
Subject: Re: [PATCH v3] ASoC: amd: add support for rt5682 codec in machine
 driver



On 3/16/21 8:37 AM, Mukunda,Vijendar wrote:
> 
> 
> On 15/03/21 9:30 pm, Pierre-Louis Bossart wrote:
>>
>>> +static int rt5682_clk_enable(struct snd_pcm_substream *substream)
>>> +{
>>> +    int ret;
>>> +    struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
>>> +
>>> +    /*
>>> +     * Set wclk to 48000 because the rate constraint of this driver is
>>> +     * 48000. ADAU7002 spec: "The ADAU7002 requires a BCLK rate that is
>>> +     * minimum of 64x the LRCLK sample rate." RT5682 is the only clk
>>> +     * source so for all codecs we have to limit bclk to 64X lrclk.
>>> +     */
>>> +    clk_set_rate(rt5682_dai_wclk, 48000);
>>> +    clk_set_rate(rt5682_dai_bclk, 48000 * 64);
>>> +    ret = clk_prepare_enable(rt5682_dai_bclk);
>>> +    if (ret < 0) {
>>> +        dev_err(rtd->dev, "can't enable master clock %d\n", ret);
>>> +        return ret;
>>> +    }
>>> +    return ret;
>>> +}
>>
>> Out of curiosity, is there a reason why you use clk_prepare_enable() 
>> for the bclk but not for the wclk?These changes were shared by codec 
>> vendor as an initial patch.
> We should use clk_prepare_enable() for wclk not for bclk.
> We will update and share the new patch.

Well the question remains: if you have two clocks and only enable one, 
why do you need to get two clocks.

Also this patch was modeled after the da7219 case, where the same open 
applies.