linux-kernel - Re: [PATCH v4 1/4] arm64/dts/qcom/sc7280: remove assigned-clock-rate property for mdp clk

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Date:   Thu, 3 Mar 2022 14:38:00 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Vinod Polimera <quic_vpolimer@...cinc.com>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Rob Clark <robdclark@...il.com>,
        Stephen Boyd <swboyd@...omium.org>, quic_kalyant@...cinc.com
Subject: Re: [PATCH v4 1/4] arm64/dts/qcom/sc7280: remove assigned-clock-rate
 property for mdp clk

Hi,

On Thu, Mar 3, 2022 at 1:40 AM Vinod Polimera <quic_vpolimer@...cinc.com> wrote:
>
> Kernel clock driver assumes that initial rate is the
> max rate for that clock and was not allowing it to scale
> beyond the assigned clock value.
>
> Drop the assigned clock rate property and vote on the mdp clock as per
> calculated value during the usecase.

I see the "Drop the assigned clock rate property" part, but where is
the "and vote on the mdp clock" part? Did it already land or
something? I definitely see that commit 5752c921d267 ("drm/msm/dpu:
simplify clocks handling") changed a bunch of this but it looks like
dpu_core_perf_init() still sets "max_core_clk_rate" to whatever the
clock was at bootup. I assume you need to modify that function to call
into the OPP layer to find the max frequency?

> Changes in v2:
> - Remove assigned-clock-rate property and set mdp clk during resume sequence.
> - Add fixes tag.
>
> Changes in v3:
> - Remove extra line after fixes tag.(Stephen Boyd)
>
> Fixes: 62fbdce91("arm64: dts: qcom: sc7280: add display dt nodes")

Having a "Fixes" is good, but presumably you need a code change along
with this, right? Otherwise if someone picks this back to stable then
they'll end up breaking, right? We need to tag / note that _somehow_.