linux-kernel - Re: [PATCH v3 06/15] dt-bindings: display/msm: sc7180-dpu: Describe SM6125

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Message-ID: <CAA8EJprHEes5T1z4-sxg_Xk+VjuyoTH0Ra-VyMnrWjTv7qG9EA@mail.gmail.com>
Date:   Thu, 20 Jul 2023 01:24:27 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Krishna Manikandan <quic_mkrishn@...cinc.com>,
        Loic Poulain <loic.poulain@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-clk@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, Lux Aliaga <they@...t.lgbt>,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v3 06/15] dt-bindings: display/msm: sc7180-dpu: Describe SM6125

On Thu, 20 Jul 2023 at 01:09, Marijn Suijten
<marijn.suijten@...ainline.org> wrote:
>
> On 2023-07-19 01:06:03, Dmitry Baryshkov wrote:
> > On 19/07/2023 00:24, Marijn Suijten wrote:
> > > SM6125 is identical to SM6375 except that while downstream also defines
> > > a throttle clock, its presence results in timeouts whereas SM6375
> > > requires it to not observe any timeouts.  This is represented by
> > > reducing the clock array length to 6 so that it cannot be passed.  Note
> > > that any SoC other than SM6375 (currently SC7180 and SM6350) are
> > > unconstrained and could either pass or leave out this "throttle" clock.
> >
> > Could you please describe, what kind of timeouts do you observe? Is this
> > the DSI underruns issue?
>
> Ping-pong timeouts and low(er) framerate.  However, they were previosuly
> not happening on a random boot out of tens... and now I can no longer
> reproduce the timeout on 4 consecutive boots after adding the throttle
> clock.  Could it perhaps be the power domains and opps that we added in
> v2 and v3?

Quite unlikely, but who knows. My main question is whether we should
continue skipping the throttle clocks or if it should be enabled now.

>
> We previously discussed in DMs that the rate was bouncing between 25MHz
> and 403MHz without the clock specified, and with it it it got set at 385
> or 403MHz.  Now, a month or so later, repeatedly running this command
> shows 25MHz when the panel is not being refreshed, and between 337 and
> 403MHz on modetest -r -v:
>
>     sony-pdx201 ~ $ sudo ./debugcc -p sm6125 gcc_disp_throttle_core_clk
>                 gcc_disp_throttle_core_clk: 337.848277MHz (337848277Hz)
>
> Either all these boots are flukes, or it is really fixed and this patch
> should be revised...
>
> > If so, it might be fixed by the MDSS
> > interconnect fix ([1]).
> >
> > [1] https://patchwork.freedesktop.org/series/116576/
>
> Might have an effect but I don't have any interconnects defined in this
> SoC DT yet.
>
> - Marijn
>
> > > Reviewed-by: Rob Herring <robh@...nel.org>
> > > Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>
> > > ---
> > >   .../devicetree/bindings/display/msm/qcom,sc7180-dpu.yaml   | 14 ++++++++++++++
> > >   1 file changed, 14 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/display/msm/qcom,sc7180-dpu.yaml b/Documentation/devicetree/bindings/display/msm/qcom,sc7180-dpu.yaml
> > > index 630b11480496..37f66940c5e3 100644
> > > --- a/Documentation/devicetree/bindings/display/msm/qcom,sc7180-dpu.yaml
> > > +++ b/Documentation/devicetree/bindings/display/msm/qcom,sc7180-dpu.yaml
> > > @@ -15,6 +15,7 @@ properties:
> > >     compatible:
> > >       enum:
> > >         - qcom,sc7180-dpu
> > > +      - qcom,sm6125-dpu
> > >         - qcom,sm6350-dpu
> > >         - qcom,sm6375-dpu
> > >
> > > @@ -73,6 +74,19 @@ allOf:
> > >           clock-names:
> > >             minItems: 7
> > >
> > > +  - if:
> > > +      properties:
> > > +        compatible:
> > > +          const: qcom,sm6125-dpu
> > > +
> > > +    then:
> > > +      properties:
> > > +        clocks:
> > > +          maxItems: 6
> > > +
> > > +        clock-names:
> > > +          maxItems: 6
> > > +
> > >   examples:
> > >     - |
> > >       #include <dt-bindings/clock/qcom,dispcc-sc7180.h>
> > >
> >
> > --
> > With best wishes
> > Dmitry
> >



-- 
With best wishes
Dmitry