linux-kernel - Re: [PATCH 13/25] ASoC: dt-bindings: meson: axg-pdm: document 'sysrate' property

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Date: Tue, 19 Mar 2024 06:17:56 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Jan Dakinevich <jan.dakinevich@...utedevices.com>,
 Jerome Brunet <jbrunet@...libre.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>,
 Kevin Hilman <khilman@...libre.com>,
 Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
 Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
 Linus Walleij <linus.walleij@...aro.org>, Jaroslav Kysela <perex@...ex.cz>,
 Takashi Iwai <tiwai@...e.com>, linux-amlogic@...ts.infradead.org,
 linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 alsa-devel@...a-project.org, linux-sound@...r.kernel.org,
 linux-gpio@...r.kernel.org, kernel@...utedevices.com
Subject: Re: [PATCH 13/25] ASoC: dt-bindings: meson: axg-pdm: document
 'sysrate' property

On 17/03/2024 16:52, Jan Dakinevich wrote:
> 
> 
> On 3/15/24 13:22, Jerome Brunet wrote:
>>
>> On Fri 15 Mar 2024 at 11:00, Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
>>
>>> On 15/03/2024 00:21, Jan Dakinevich wrote:
>>>> This option allow to redefine the rate of DSP system clock.
>>>
>>> And why is it suitable for bindings? Describe the hardware, not what you
>>> want to do in the driver.
>>>
>>>>
>>>> Signed-off-by: Jan Dakinevich <jan.dakinevich@...utedevices.com>
>>>> ---
>>>>  Documentation/devicetree/bindings/sound/amlogic,axg-pdm.yaml | 4 ++++
>>>>  1 file changed, 4 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/sound/amlogic,axg-pdm.yaml b/Documentation/devicetree/bindings/sound/amlogic,axg-pdm.yaml
>>>> index df21dd72fc65..d2f23a59a6b6 100644
>>>> --- a/Documentation/devicetree/bindings/sound/amlogic,axg-pdm.yaml
>>>> +++ b/Documentation/devicetree/bindings/sound/amlogic,axg-pdm.yaml
>>>> @@ -40,6 +40,10 @@ properties:
>>>>    resets:
>>>>      maxItems: 1
>>>>  
>>>> +  sysrate:
>>>> +    $ref: /schemas/types.yaml#/definitions/uint32
>>>> +    description: redefine rate of DSP system clock
>>>
>>> No vendor prefix, so is it a generic property? Also, missing unit
>>> suffix, but more importantly I don't understand why this is a property
>>> of hardware.
>>
>> +1.
>>
>> The appropriate way to set rate of the clock before the driver take over
>> is 'assigned-rate', if you need to customize this for different
>> platform.
>>
> 
> It would be great, but it doesn't work. Below, is what I want to see:
> 
> 	assigned-clocks =
> 		<&clkc_audio AUD2_CLKID_PDM_SYSCLK_SEL>,
> 		<&clkc_audio AUD2_CLKID_PDM_SYSCLK_DIV>;
> 	assigned-clock-parents =
> 		<&clkc_pll CLKID_FCLK_DIV3>,
> 		<0>;
> 	assigned-clock-rates =
> 		<0>,
> 		<256000000>;
> 
> But regardles of this declaration, PDM's driver unconditionally sets

That's driver's problem. You do not change bindings, just because your
driver behaves differently. Just fix driver.

> sysclk'rate to 250MHz and throws away everything that was configured
> before, reparents audio2_pdm_sysclk_mux to hifi_pll and changes
> hifi_pll's rate.
> 
> This value 250MHz is declared here:
> 
> static const struct axg_pdm_cfg axg_pdm_config = {
> 	.filters = &axg_default_filters,
> 	.sys_rate = 250000000,
> };
> 
> The property 'sysrate' is intended to redefine hardcoded 'sys_rate'
> value in 'axg_pdm_config'.

What does it have to do with bindings? Change driver if you are not
happy how it operates.

Best regards,
Krzysztof