linux-kernel - Re: [PATCH v3 1/8] dt-bindings: arm: qcom: Document MSM8939 SoC binding

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Message-ID: <Y8eyIO8BqKzvulbB@gerhold.net>
Date:   Wed, 18 Jan 2023 09:47:28 +0100
From:   Stephan Gerhold <stephan@...hold.net>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Cc:     agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org,
        djakov@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, benl@...areup.com,
        shawn.guo@...aro.org, fabien.parent@...aro.org, leo.yan@...aro.org,
        dmitry.baryshkov@...aro.org,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH v3 1/8] dt-bindings: arm: qcom: Document MSM8939 SoC
 binding

On Tue, Jan 17, 2023 at 02:48:39AM +0000, Bryan O'Donoghue wrote:
> Document the MSM8939 and supported boards in upstream Sony "Tulip" M4 Aqua
> and Square APQ8039 T2.
> 
> MSM8939 is one of the older SoCs so we need to expand the list of
> qcom,board-ids to allow for the bootloader DTS board-id matching
> dependency.
> 

The original LK bootloaders cannot boot your msm8939.dtsi correctly,
because a spin-table implementation is required to get the other CPU
cores up. This means that a modified bootloader is always needed from
the upstream point of view, since I doubt anyone wants to use these
devices with a single core only. lk2nd (as the primary spin-table
implementation right now) has never required qcom,board-ids and any
custom LK would be easy to patch to ignore these.

Do you already have a bootloader with spin-table support deployed in the
field that can be no longer easily modified to ignore the qcom,board-id?

If not, and you're planning to keep using the downstream patches to
bring the CPU cores up without spin-table/PSCI then you might as well
add the qcom,board-id as downstream patch as well.

If we don't support the original bootloaders in a usable way upstream
then we should not add MSM8939 to the allow list of broken bootloaders
either, in my opinion.

Thanks,
Stephan