| Message ID | 20241008-fix-sm8x50-mdp-icc-v1-1-77ffd361b8de@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: dts: qcom: sm8[56]50: correct MDSS interconnects | expand |
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
diff --git a/arch/arm64/boot/dts/qcom/sm8550.dtsi b/arch/arm64/boot/dts/qcom/sm8550.dtsi index 9dc0ee3eb98f..cca10f9faa14 100644 --- a/arch/arm64/boot/dts/qcom/sm8550.dtsi +++ b/arch/arm64/boot/dts/qcom/sm8550.dtsi @@ -2871,9 +2871,8 @@ mdss: display-subsystem@ae00000 { power-domains = <&dispcc MDSS_GDSC>; - interconnects = <&mmss_noc MASTER_MDP 0 &gem_noc SLAVE_LLCC 0>, - <&mc_virt MASTER_LLCC 0 &mc_virt SLAVE_EBI1 0>; - interconnect-names = "mdp0-mem", "mdp1-mem"; + interconnects = <&mmss_noc MASTER_MDP 0 &mc_virt SLAVE_EBI1 0>; + interconnect-names = "mdp0-mem"; iommus = <&apps_smmu 0x1c00 0x2>;
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 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: d7da51db5b81 ("arm64: dts: qcom: sm8550: add display hardware devices") Cc: stable@kernel.org Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> --- arch/arm64/boot/dts/qcom/sm8550.dtsi | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)