linux-kernel - Re: Removal of qcom,board-id and qcom,msm-id

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Message-ID: <35051bec-98ea-b4c5-f734-06b3f22f3562@linaro.org>
Date:   Thu, 19 May 2022 14:39:39 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh@...nel.org>, Stephen Boyd <sboyd@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Andy Gross <agross@...nel.org>,
        Olof Johansson <olof@...om.net>
Cc:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Removal of qcom,board-id and qcom,msm-id

On 19/05/2022 13:44, Krzysztof Kozlowski wrote:
> Hi,
> 
> There was an old effort of removal of qcom,board-id and qcom,msm-id
> properties from Qualcomm SoC-based boards like [1].
> 
> First approach was to document them, which (obviously) was not well
> received [2] [3] [4].
> 
> The solution from Stephen was to encode these in the board compatible,
> so bootloader can extract that information. That seemed to receive
> positive comments, at least from Rob. [5]
> 
> It was 2015... ~7 years later we are still things doing the same way,
> still with undocumented properties: qcom,board-id and qcom,msm-id.
> 
> 
> I would like to revive that topic, but before I start doing something
> pointless - any guidance on last patch from Stephen [5]? Was it ok? Some
> early NAKs?

I do not quite fancy the idea of using extra tools to process dtb files. 
At this moment it is possible to concatenate several kernel-generated 
dtb files together. AOSP developers use this to have an image that boots 
on both RB3 and RB5 boards.

I think that changing compat strings only makes sense if Qualcomm would 
use such compat strings in future. Otherwise we end up in a position 
where we have custom bootloaders for the RB3/RB5/etc, but the majority 
of the board requires extra processing steps.

So, I think, we should drop the unspecified usid aliases, document the 
board-id/msm-id/pmic-id properties and stick with them. They might be 
ugly, but they are expected/processed by the majority of devices present 
in the wild.

> [1]
> https://elixir.bootlin.com/linux/v5.18-rc7/source/arch/arm64/boot/dts/qcom/sdm845-oneplus-fajita.dts#L14
> 
> [2] https://lore.kernel.org/all/7229476.C4So9noUlf@wuerfel/
> [3]
> https://lore.kernel.org/all/1450371534-10923-20-git-send-email-mtitinger+renesas@baylibre.com/
> [4] https://lore.kernel.org/all/20151119153640.GC893@linaro.org/
> [5]
> https://lore.kernel.org/all/1448062280-15406-1-git-send-email-sboyd@codeaurora.org/
> 
> Best regards,
> Krzysztof


-- 
With best wishes
Dmitry