linux-kernel - Re: [PATCH 1/2] arm64: dts: qcom: sm8550: correct MDSS interconnects

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Message-ID: <2cf6ca44-3a7c-4561-91db-5493414d61ec@oss.qualcomm.com>
Date: Fri, 25 Oct 2024 23:53:04 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>
Cc: Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Rob Clark
 <robdclark@...il.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, freedreno@...ts.freedesktop.org,
        stable@...nel.org
Subject: Re: [PATCH 1/2] arm64: dts: qcom: sm8550: correct MDSS interconnects

On 8.10.2024 1:36 AM, Dmitry Baryshkov wrote:
> SM8550 lists two interconnects for the display subsystem, mdp0-mem
> (between MDP and LLCC) and mdp1-mem (between LLCC and EBI, memory).
> The second interconnect is a misuse. mdpN-mem paths should be used for
> several outboud MDP interconnects rather than the path between LLCC and
> memory. This kind of misuse can result in bandwidth underflows, possibly
> degradating picture quality as the required memory bandwidth is divided

degrading

> between all mdpN-mem paths (and LLCC-EBI should not be a part of such
> division).

I think it's just for power savings, but maybe Abhinav would know
better

Konrad