linux-kernel - Re: [PATCH 1/2] dt-bindings: arm: fsl: Update i.MX95 compatible

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Message-ID: <eb85b7db-cd17-4dc0-8b0f-73bbf6ac8e37@kernel.org>
Date: Mon, 13 Jan 2025 12:35:35 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Peng Fan <peng.fan@....nxp.com>
Cc: Peng Fan <peng.fan@....com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
 Sascha Hauer <s.hauer@...gutronix.de>,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
 Fabio Estevam <festevam@...il.com>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
 "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] dt-bindings: arm: fsl: Update i.MX95 compatible

On 09/01/2025 03:40, Peng Fan wrote:
> On Mon, Jan 06, 2025 at 07:12:29AM +0100, Krzysztof Kozlowski wrote:
>> On 06/01/2025 03:51, Peng Fan wrote:
>>>> Subject: Re: [PATCH 1/2] dt-bindings: arm: fsl: Update i.MX95
>>>> compatible
>>>>
>>>> On 04/01/2025 13:13, Peng Fan (OSS) wrote:
>>>>> From: Peng Fan <peng.fan@....com>
>>>>>
>>>>> i.MX95 features a System Controller and SCMI Spec 3.2 compatible
>>>>> firmware System Manager(SM) runs on the controller.
>>>>> Add "fsl,imx-sm" compatible string as fallback for "fsl,imx95" to
>>>>> indicate it is compatible with i.MX System Manager.
>>>>
>>>> I see little value in generic compatible like that. All these are
>>>> aarch64 so why not adding that compatible?
>>>>
>>>> How this generic compatible would be used?
>>>>
>>>> And by what exactly?
>>>
>>> There will be more i.MX9 chips with System Manager. I would
>>> not expand the list here each time to support a new SoC.
>>>
>>> https://elixir.bootlin.com/linux/v6.13-rc3/source/drivers/pinctrl/pinctrl-scmi.c#L508
>>> https://elixir.bootlin.com/linux/v6.13-rc3/source/drivers/pinctrl/freescale/pinctrl-imx-scmi.c#L290
>>
>> Problem is that compatible is way too generic to be used by Linux drivers.
> 
> Is "fsl,imx9-sm" feasible here?

It is better, but I am still not happy with the generic meaning of it.
You claim now that certain SoCs will be compatible with imx9-sm, so with
some sort of "sm". What is the meaning of sm in terms of ABI and
interfaces? What do you exactly define here? And what happens if some
other feature will require one more compatible and then one more?

You will have:
compatible = "fsl,imx95-19x19-evk", "fsl,imx95", "fsl,imx9-sm",
"fsl,imx9-foo", "fsl,imx9-bar", "fsl,imx9-whatnot";

You add compatible for some unspecified interface called "System
Manager" just to solve Linux driver issue.

Best regards,
Krzysztof