linux-kernel - Re: [PATCH 7/9] ARM: dts: stm32: add Hardware debug port (HDP) on stm32mp25

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Message-ID: <8cdc7e52-f9e2-4fc9-be68-0dd72a25ee1b@foss.st.com>
Date: Wed, 26 Feb 2025 16:30:19 +0100
From: Alexandre TORGUE <alexandre.torgue@...s.st.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
        Clement LE GOFFIC
	<clement.legoffic@...s.st.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Rob
 Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor
 Dooley <conor+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Bartosz Golaszewski <brgl@...ev.pl>
CC: <linux-kernel@...r.kernel.org>, <linux-gpio@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 7/9] ARM: dts: stm32: add Hardware debug port (HDP) on
 stm32mp25



On 2/26/25 16:08, Krzysztof Kozlowski wrote:
> On 26/02/2025 10:33, Alexandre TORGUE wrote:
>>>>>> +		hdp: pinctrl@...90000 {
>>>>>> +			compatible = "st,stm32mp-hdp";
>>>>>
>>>>> So here again - you have stm32mp251 SoC, but use entirely different
>>>>> compatible.
>>>>
>>>> Ok so I will use "st,stm32mp15-hdp"
>>>
>>>
>>> This means this is stm32mp15 SoC. I do not see such SoC on list of your
>>> SoCs in bindings. What's more, there are no bindings for other SoC
>>> components for stm32mp15!
>>
>> Yes stm32mp15 is not a "real SoC". I agree that at the beginning of the
>> STM32 story we didn't have a clear rule/view to correctly naming our
>> compatible. We tried to improve the situation to avoid compatible like
>> "st,stm32", "st,stm32mp" or "st,stm32mp1". So we introduced
>> "st,stm32mp13", "st,stm32mp15" or "st,stm32mp25" for new drivers. So yes
>> it represents a SoC family and not a real SoC. We haven't had much
>> negative feedback it.
>>
>> But, if it's not clean to do it in this way, lets define SoC compatible
>> for any new driver.
> 
> Compatibles are for hardware.
> 
>> For the HDP case it is: "st,stm32mp157" and used for STM32MP13,
>> STM32MP15 end STM32MP25 SoC families (if driver is the same for all
>> those SoCs).
> 
> No, it's three compatibles, because you have three SoCs. BTW, writing
> bindings (and online resources and previous reviews and my talks) are
> saying that, so we do not ask for anything new here, anything different.
> At least not new when looking at last 5 years, because 10 years ago many
> rules were relaxed...

So adding 3 times the same IP in 3 different SoCs implies to have 3 
different compatibles. So each time we use this same IP in a new SoC, we 
have to add a new compatible. My (wrong) understanding was: as we have 
the same IP (same hardware) in each SoC we have the same compatible (and 
IP integration differences (clocks, interrupts) are handled by DT 
properties.

> 
> 
> Best regards,
> Krzysztof