linux-kernel - Re: [PATCH 1/3] ASoC: simple-card-utils: Fix device module clock

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Date:   Tue, 9 Mar 2021 21:57:58 +0530
From:   Sameer Pujar <spujar@...dia.com>
To:     Michael Walle <michael@...le.cc>
CC:     <alsa-devel@...a-project.org>, <broonie@...nel.org>,
        <devicetree@...r.kernel.org>, <jonathanh@...dia.com>,
        <kuninori.morimoto.gx@...esas.com>, <linux-kernel@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <robh@...nel.org>,
        <sharadg@...dia.com>, <thierry.reding@...il.com>
Subject: Re: [PATCH 1/3] ASoC: simple-card-utils: Fix device module clock

Hi Michael,

On 3/9/2021 8:11 PM, Michael Walle wrote:
> External email: Use caution opening links or attachments
>
>
> Hi,
>
>> If "clocks = <&xxx>" is specified from the CPU or Codec component
>> device node, the clock is not getting enabled. Thus audio playback
>> or capture fails.
>>
>> Fix this by populating "simple_dai->clk" field when clocks property
>> is specified from device node as well. Also tidy up by re-organising
>> conditional statements of parsing logic.
>>
>> Fixes: bb6fc620c2ed ("ASoC: simple-card-utils: add asoc_simple_card_parse_clk()")
>> Cc: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
>> Signed-off-by: Sameer Pujar <spujar@...dia.com>
> This actually breaks sound on my board
> (arch/arm64/boot/dts/freescale/fsl-ls1028a-kontron-sl28-var3-ads2.dts).
> The codec on this board (wm8904) has a fixed clock input (only distinct
> frequencies are supported) and uses the FLL of the codec to generate the
> desired sample rate.
>
> It seems that after this patch the clock rate of the codecs clock (rather
> than the FLL) is tried to be changed. Which fails, because it doesn't
> support arbitrary frequencies.

Yes, after the given change the clock will be updated if "*mclk-fs" 
property is specified.

DT you mentioned has property "simple-audio-card,mclk-fs = <256>", which 
means you need a clock that is a function of sample rate. But as per 
above you want a fixed clock for MCLK. I think if you drop this 
property, the clock updates won't happen. Earlier for your case, this 
property was not used at all because the clock handle was not populated.

>
> -michael
>
>> ---
>>   sound/soc/generic/simple-card-utils.c | 13 ++++++-------
>>   1 file changed, 6 insertions(+), 7 deletions(-)
>>
>> diff --git a/sound/soc/generic/simple-card-utils.c b/sound/soc/generic/simple-card-utils.c
>> index bc0b62e..0754d70 100644
>> --- a/sound/soc/generic/simple-card-utils.c
>> +++ b/sound/soc/generic/simple-card-utils.c
>> @@ -173,16 +173,15 @@ int asoc_simple_parse_clk(struct device *dev,
>>         *  or device's module clock.
>>         */
>>        clk = devm_get_clk_from_child(dev, node, NULL);
>> -     if (!IS_ERR(clk)) {
>> -             simple_dai->sysclk = clk_get_rate(clk);
>> +     if (IS_ERR(clk))
>> +             clk = devm_get_clk_from_child(dev, dlc->of_node, NULL);
>>
>> +     if (!IS_ERR(clk)) {
>>                simple_dai->clk = clk;
>> -     } else if (!of_property_read_u32(node, "system-clock-frequency", &val)) {
>> +             simple_dai->sysclk = clk_get_rate(clk);
>> +     } else if (!of_property_read_u32(node, "system-clock-frequency",
>> +                                      &val)) {
>>                simple_dai->sysclk = val;
>> -     } else {
>> -             clk = devm_get_clk_from_child(dev, dlc->of_node, NULL);
>> -             if (!IS_ERR(clk))
>> -                     simple_dai->sysclk = clk_get_rate(clk);
>>        }
>>
>>        if (of_property_read_bool(node, "system-clock-direction-out"))
>> --
>> 2.7.4
>>
>>