linux-kernel - [PATCH v2 2/2] arm64: dts: qcom: sm8650: correct MDSS interconnects

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Message-Id: <20241026-fix-sm8x50-mdp-icc-v2-2-fd8ddf755acc@linaro.org>
Date: Sat, 26 Oct 2024 20:59:41 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: 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: [PATCH v2 2/2] arm64: dts: qcom: sm8650: correct MDSS
 interconnects

SM8650 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
degrading picture quality as the required memory bandwidth is divided
between all mdpN-mem paths (and LLCC-EBI should not be a part of such
division).

Drop the second path and use direct MDP-EBI path for mdp0-mem until we
support separate MDP-LLCC and LLCC-EBI paths.

Fixes: 10e024671295 ("arm64: dts: qcom: sm8650: add interconnect dependent device nodes")
Cc: stable@...nel.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
---
 arch/arm64/boot/dts/qcom/sm8650.dtsi | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/sm8650.dtsi b/arch/arm64/boot/dts/qcom/sm8650.dtsi
index 173e092b15e2..4b54063c0e0c 100644
--- a/arch/arm64/boot/dts/qcom/sm8650.dtsi
+++ b/arch/arm64/boot/dts/qcom/sm8650.dtsi
@@ -3455,11 +3455,8 @@ mdss: display-subsystem@...0000 {
 			resets = <&dispcc DISP_CC_MDSS_CORE_BCR>;
 
 			interconnects = <&mmss_noc MASTER_MDP QCOM_ICC_TAG_ALWAYS
-					 &gem_noc SLAVE_LLCC QCOM_ICC_TAG_ALWAYS>,
-					<&mc_virt MASTER_LLCC QCOM_ICC_TAG_ALWAYS
 					 &mc_virt SLAVE_EBI1 QCOM_ICC_TAG_ALWAYS>;
-			interconnect-names = "mdp0-mem",
-					     "mdp1-mem";
+			interconnect-names = "mdp0-mem";
 
 			power-domains = <&dispcc MDSS_GDSC>;
 

-- 
2.39.5