linux-kernel - Re: [PATCH v2] memory: renesas-rpc-if: Fix PHYCNT.STRTIM setting

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Message-ID: <1692b03b-bb93-abba-82a6-ab5a1a6fcc37@linaro.org>
Date:   Thu, 26 Jan 2023 10:51:12 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        linux-renesas-soc@...r.kernel.org,
        Prabhakar <prabhakar.csengg@...il.com>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] memory: renesas-rpc-if: Fix PHYCNT.STRTIM setting

On 26/01/2023 10:27, Geert Uytterhoeven wrote:
>>> I did not get whether this is runtime characteristics or it can be
>>> customized with compatible (just you did not do it)?
>>
>> We have compatibles per SoC, i.e. "r8a7795". We don't have compatibles
>> for ES versions, i.e. no "r8a7795-es10" or "r8a7795-es20".
>>
>> The latter would not be practical. We can't know in advance how many ES
>> revisions there will be, so we can't prepare DTs accordingly. Updating
>> later would be also difficult because we are usually not notified if
>> there is a new ES version. Only if there are problems with it. And which
>> board is available with which ES version is chaotic^2.
>>
>> Also, if we update DTs later, old DTBs would not work with newer kernels
>> (requiring a later added compaible for a new ES version). This all still
>> ignores that it would be a churn to update for every ES version of every
>> SoC. We have quite many to support. That's why we use soc_device_match()
>> for ES versions in many places alreday. It was never a problem so far.
>>
>> That's my reasoning, probably Geert has something to add. He maintains
>> the Renesas DT files.
> 
> Exactly. We only use soc_device_match() to distinguish where we do not
> have a compatible value to do so.  As we have SoC-specific compatible
> values for about everything, this means we usually use soc_device_match()
> only to handle quirks on specific revisions of SoCs.
> 

OK, thank you both for clarifying.

Best regards,
Krzysztof