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

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Date:   Thu, 11 Mar 2021 11:27:51 +0100
From:   Michael Walle <michael@...le.cc>
To:     Sameer Pujar <spujar@...dia.com>
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 Sameer,

Am 2021-03-10 15:50, schrieb Sameer Pujar:
> On 3/10/2021 4:00 AM, Michael Walle wrote:
>> Am 2021-03-09 17:27, schrieb Sameer Pujar:
>>> On 3/9/2021 8:11 PM, Michael Walle wrote:
>>>>> 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.
>> 
>> You mean to drop the mclk-fs property? I can't do that because I
>> actually need a frequency of 256 * sample rate. But that doesn't
>> necessarily need to be the MCLK, because the codec itself has a
>> FLL/PLL which can be used to generate any frequency for a given
>> MCLK. So that is a valid scenario. See also commit 13409d27cb39
>> ("ASoC: wm8904: configure sysclk/FLL automatically").
>> 

I've had a closer look at this and it seems you're messing around
with the clock of the codec's node (which is _not_ a subnode of
the simple-audio-card). I don't think this is correct.

I guess you should rather set the clock property in the codec
subnode of the simple-audio-card, which is then picked up by the
simple-audio-card driver and changed accordingly.

For example:
		simple-audio-card,dai-link@0 {
			reg = <0>;
			bitclock-master = <&dailink0_master>;
			frame-master = <&dailink0_master>;
			format = "i2s";

			cpu {
				sound-dai = <&sai6>;
			};

			dailink0_master: codec {
				sound-dai = <&wm8904>;
				clocks = <&mclk>;
			};
		};

In this case mclk will be enabled and disabled accordingly.

Could you test this?

-michael