linux-kernel - Re: Qualcomm Kryo core compatibles

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Message-ID: <CAL_JsqLYdyqe+=zb_sDOcffbbb3AUhxsCbUp_1GHk1fKu2xiJw@mail.gmail.com>
Date:   Fri, 10 Mar 2023 16:39:57 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        dt <devicetree@...r.kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Subject: Re: Qualcomm Kryo core compatibles

On Wed, Mar 8, 2023 at 4:44 AM Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
>
> Hi!
>
> I was recently debating what to do about Qualcomm Kryo compatibles.
>
> There are basically 3 cases:
>
> 1. Falkor/"real Kryo" - the (never shipped?) server platform & MSM8996
>
> This one's easy, it's actually Kryo so it should stay Kryo.
>
>
> 2. Fake Kryo ("customized" Arm Cortex cores) (MSM8998-SM8x50)
>
> This one's tough.. Qualcomm marketing material seems to sometimes say
> Cortex, sometimes Kryo, sometimes "customized Cortex".. They do use
> their own arm IMPLEMENTER_ID in the MIDR_EL1 register and their
> PART_NUM values are not Arm-stock, but these cores don't seem to be
> any special.. Maybe some irq lines are routed differently? Not sure.
>
> My proposition here is to do:
>
> "qcom,kryoXXX", "arm,cortex-ABC"
>
> or
>
> "qcom,kryoXXX-PQR", "arm,cortex-ABC"

I don't see much value in the fallback here. We don't do much with the
values anyways as everything uses ID registers anyways. Do you know
the level of modification?

> where PQR is one of:
> - silver (LITTLE cores)
> - gold (big cores)
> - gold_plus (prime core(s))
>
>
> 3. Arm cores modified within Arm implementation-defined allowance (SC8280XP+)
>
> These cores report Arm IMPLEMENTER_IDs and actual Arm PART_NUMs, which would
> suggest they're bone stock Arm Cortex cores, with some Qualcomm-iness coming
> as part of implementation details which are.. expected since Cortex allows for
> some IMPLEMENTATION DEFINED things. The only non-obvious part here is that
> the REVISION field they report does not always seem covered by the Arm TRMs.
>
> In this case I think going with
>
> "arm,cortex-ABC"
>
> is fine.. I already did this for 8550 and 8280xp and Rob seems to have liked it.
>
> So, I suppose the real question is what to do about 2., should they stay as
> they are, or maybe my proposition seems attractive?

What about the generic 'qcom,kryo' strings?

Rob