linux-kernel - Re: [PATCH 3/9] arm64: dts: qcom: sc7280: Enable MDP turbo mode

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Date: Thu, 22 Feb 2024 07:04:23 -0800
From: Bjorn Andersson <quic_bjorande@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Konrad Dybcio <konrad.dybcio@...aro.org>,
        Douglas Anderson
	<dianders@...omium.org>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar
	<quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, "Daniel
 Vetter" <daniel@...ll.ch>,
        <cros-qcom-dts-watchers@...omium.org>,
        "Bjorn
 Andersson" <andersson@...nel.org>,
        Rob Herring <robh@...nel.org>,
        "Krzysztof
 Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley
	<conor+dt@...nel.org>, <linux-arm-msm@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <freedreno@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH 3/9] arm64: dts: qcom: sc7280: Enable MDP turbo mode

On Thu, Feb 22, 2024 at 11:46:26AM +0200, Dmitry Baryshkov wrote:
> On Thu, 22 Feb 2024 at 11:28, Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
> >
> >
> >
> > On 2/22/24 10:04, Dmitry Baryshkov wrote:
> > > On Thu, 22 Feb 2024 at 10:56, Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
> > >>
> > >>
> > >>
> > >> On 2/22/24 00:41, Dmitry Baryshkov wrote:
> > >>> On Thu, 22 Feb 2024 at 01:19, Bjorn Andersson <quic_bjorande@...cinc.com> wrote:
> > >>>>
> > >>>> The max frequency listed in the DPU opp-table is 506MHz, this is not
> > >>>> sufficient to drive a 4k@60 display, resulting in constant underrun.
> > >>>>
> > >>>> Add the missing MDP_CLK turbo frequency of 608MHz to the opp-table to
> > >>>> fix this.
> > >>>
> > >>> I think we might want to keep this disabled for ChromeOS devices. Doug?
> > >>
> > >> ChromeOS devices don't get a special SoC
> > >
> > > But they have the sc7280-chrome-common.dtsi, which might contain a
> > > corresponding /delete-node/ .
> >
> > What does that change? The clock rates are bound to the
> > SoC and the effective values are limited by link-frequencies
> > or the panel driver.
> 
> Preventing the DPU from overheating? Or spending too much power?
> 

Perhaps I'm misunderstanding the implementation then, are we always
running at the max opp? I thought the opp was selected based on the
current need for performance?

Regards,
Bjorn

> -- 
> With best wishes
> Dmitry