Re: [PATCHv4 7/9] ASoC: fsl-asoc-card: add DT clock "cpu_sysclk" with generic codec

Elinor Montmasson
2024-05-31T12:47:03Z

From: "Mark Brown" <broonie@kernel.org>
Sent: Friday, 17 May, 2024 13:17:20
> On Fri, May 17, 2024 at 05:05:35AM -0400, Elinor Montmasson wrote:
>> From: "Mark Brown" <broonie@kernel.org>
>> > On Wed, May 15, 2024 at 03:54:09PM +0200, Elinor Montmasson wrote:
>
>> >> + struct clk *cpu_sysclk = clk_get(&pdev->dev, "cpu_sysclk");
>> >> + if (!IS_ERR(cpu_sysclk)) {
>> >> + priv->cpu_priv.sysclk_freq[TX] = clk_get_rate(cpu_sysclk);
>> >> + priv->cpu_priv.sysclk_freq[RX] = priv->cpu_priv.sysclk_freq[TX];
>> >> + clk_put(cpu_sysclk);
>> >> + }
>
>> > I don't really understand the goal here - this is just reading whatever
>> > frequency happens to be set in the hardware when the driver starts up
>> > which if nothing else seems rather fragile?
>
>> The driver allow to set the sysclk frequency
>> of the CPU DAI through `priv->cpu_priv.sysclk_freq` when calling
>> `fsl_asoc_card_hw_params()`.
>> Currently it is hard-coded per use-case in the driver.
>
>> My reasoning was that with a generic codec/compatible, there might
>> be use-cases needing to use this parameter, so I exposed it here via DT.
>
>> Is it a bad idea to expose this parameter ? This is not a requirement for the
>> driver to work, most of the current compatibles do not use this parameter.
>> It is currently used only for `fsl,imx-audio-cs42888`.
>> In that case I can remove this commit.
>
> I'm having a hard time connecting your reply here with my comment. This
> isn't as far as I can see allowing the frequency to be explicitly
> configured, it's just using whatever value happens to be programmed in
> the clock when the driver starts.

In v3 I used parameters `cpu-sysclk-freq-rx/tx` to explicitly
set the frequency.
In its review Rob Herring said that the clock bindings should
be used, so that's why I changed it to use this `cpu_sysclk` clock.