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

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Date: Tue, 19 Mar 2024 03:35:14 +0300
From: Jan Dakinevich <jan.dakinevich@...utedevices.com>
To: Jerome Brunet <jbrunet@...libre.com>
CC: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, 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 3/18/24 13:55, Jerome Brunet wrote:
> 
> On Sun 17 Mar 2024 at 18:52, Jan Dakinevich <jan.dakinevich@...utedevices.com> 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
>> 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 is stopping you from removing that from the driver and adding
> assigned-rate to 250M is the existing platform ?
> 

Ok, in next version I will try to remove this unconditional setting of
rate that spoils my clock hierarchy.

>>
>>> Then you don't have to deal with it in the device driver.
>>>
>>>>
>>>> Best regards,
>>>> Krzysztof
>>>
>>>
> 
> 

-- 
Best regards
Jan Dakinevich