linux-kernel - Re: [PATCH 5/8] pwm: stm32-lp: add support for stm32mp25

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Message-ID: <e15754dd-5f4e-424d-a3a9-308dae814708@kernel.org>
Date: Wed, 26 Feb 2025 08:54:03 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
Cc: lee@...nel.org, ukleinek@...nel.org, alexandre.torgue@...s.st.com,
 robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, wbg@...nel.org,
 jic23@...nel.org, daniel.lezcano@...aro.org, tglx@...utronix.de,
 catalin.marinas@....com, will@...nel.org, devicetree@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-iio@...r.kernel.org, linux-pwm@...r.kernel.org,
 olivier.moysan@...s.st.com
Subject: Re: [PATCH 5/8] pwm: stm32-lp: add support for stm32mp25

On 25/02/2025 15:58, Fabrice Gasnier wrote:
> 
> 
> On 2/25/25 13:04, Krzysztof Kozlowski wrote:
>> On Mon, Feb 24, 2025 at 07:01:47PM +0100, Fabrice Gasnier wrote:
>>>  	}
>>>  
>>>  	return pinctrl_pm_select_sleep_state(dev);
>>> @@ -246,6 +413,7 @@ static DEFINE_SIMPLE_DEV_PM_OPS(stm32_pwm_lp_pm_ops, stm32_pwm_lp_suspend,
>>>  
>>>  static const struct of_device_id stm32_pwm_lp_of_match[] = {
>>>  	{ .compatible = "st,stm32-pwm-lp", },
>>> +	{ .compatible = "st,stm32mp25-pwm-lp", },
>>
>> No driver data suggests device is backwards compatible. Commit msg
>> suggests not, so that's confusing.
> 
> 
> The LPTimer PWM driver takes benefit of the MFD parent driver to feed in
> data, e.g. 'num_cc_chans'. Number of channels is now variable, on

This means this ID table is useless. You do the matching via parent
device, so stop growing the table and call it deprecated or something.

> STM32MP25 (e.g. not a single channel). But it can't be hard-coded as
> compatible data. (there's only 1 channel on earlier LP Timer hardware
> revision).
> 
> The hardware controller is a bit different, hence the new compatible

If it works with old compatible, it's an easy proof that it is
compatible, so please counter argument that with something specific.
What is different that driver cannot work with new device using old
interface or old features?


Best regards,
Krzysztof