linux-kernel - Re: [PATCH 1/2] ASoC: rt5640: Update MCLK rate in set

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Date:   Fri, 10 Feb 2023 14:00:55 +0530
From:   Sameer Pujar <spujar@...dia.com>
To:     Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
Cc:     robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        thierry.reding@...il.com, jonathanh@...dia.com,
        oder_chiou@...ltek.com, broonie@...nel.org, perex@...ex.cz,
        tiwai@...e.com, lgirdwood@...il.com, devicetree@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org
Subject: Re: [PATCH 1/2] ASoC: rt5640: Update MCLK rate in set_sysclk()

Hi Morimoto-san,

On 10-02-2023 05:12, Kuninori Morimoto wrote:
>
>> Simple-card/audio-graph-card drivers do not handle MCLK clock when it
>> is specified in the codec device node. The expectation here is that,
>> the codec should actually own up the MCLK clock and do necessary setup
>> in the driver.
> I have no objection about this patch, but have interesting about this comment.
>
> Simple-card/audio-graph-card both are using asoc_simple_hw_params,
> and it calls clk_set_rate() for Codec/CPU if it has mclk.
> But am I misunderstanding ?
> If it was simple-card-utils side miss, I'm happy to fix it.

The simple-card-utils driver does not populate the clock handle whenever 
the MCLK clock is parsed from CODEC device node. So 
asoc_simple_set_clk_rate() will not update the rate and clock 
enable/disable won't happen either.Initially I had tried to fix this in 
the simple-card-utils itself and it did break few things on other HW.
Please see [0] for relevant discussion.

Later [1] was pushed to address the issue I was facing that time.

In summary, the suggestion was, clock property should be associated with 
only devices and device driver should own up the clock handling for it. 
The machine driver can just pass the required configuration for it.

[0] 
https://patchwork.ozlabs.org/project/linux-tegra/patch/1612939421-19900-2-git-send-email-spujar@nvidia.com/#2647112
[1] 
https://lore.kernel.org/lkml/1615829492-8972-3-git-send-email-spujar@nvidia.com/