Re: [PATCH v2 8/8] arm64: dts: qcom: sm8450: provide MDSS cfg interconnect

[Konrad Dybcio <konrad.dybcio@linaro.org>]

On 12.07.2023 14:11, Dmitry Baryshkov wrote:
> Add support for the MDSS cfg-cpu bus vote on the SM8450 platform.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>  arch/arm64/boot/dts/qcom/sm8450.dtsi | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sm8450.dtsi b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> index 595533aeafc4..0b01f3027ee3 100644
> --- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> @@ -13,6 +13,7 @@
>  #include <dt-bindings/mailbox/qcom-ipcc.h>
>  #include <dt-bindings/phy/phy-qcom-qmp.h>
>  #include <dt-bindings/power/qcom-rpmpd.h>
> +#include <dt-bindings/interconnect/qcom,icc.h>
>  #include <dt-bindings/interconnect/qcom,sm8450.h>
>  #include <dt-bindings/soc/qcom,gpr.h>
>  #include <dt-bindings/soc/qcom,rpmh-rsc.h>
> @@ -2672,8 +2673,12 @@ mdss: display-subsystem@ae00000 {
>  
>  			/* same path used twice */
>  			interconnects = <&mmss_noc MASTER_MDP_DISP 0 &mc_virt SLAVE_EBI1_DISP 0>,
> -					<&mmss_noc MASTER_MDP_DISP 0 &mc_virt SLAVE_EBI1_DISP 0>;
> -			interconnect-names = "mdp0-mem", "mdp1-mem";
> +					<&mmss_noc MASTER_MDP_DISP 0 &mc_virt SLAVE_EBI1_DISP 0>,
> +					<&gem_noc MASTER_APPSS_PROC QCOM_ICC_TAG_ACTIVE_ONLY
> +					 &config_noc SLAVE_DISPLAY_CFG QCOM_ICC_TAG_ACTIVE_ONLY>;
Looking at icc_set_tag occurences in msm-5.10/techpack/display,
I *think* active-only is only possible for the data bus (MDP-EBI)

Moreover, I think Linux is supposed to cast MDSS votes through the
APPS RSC (so, nodes without _DISP [1][2]) and conversely, DISP_RSC is
supposed to active-only votes

Konrad

[1] not that it matters today because it's not implemented yet
[2] https://lore.kernel.org/linux-arm-msm/20230708-topic-rpmh_icc_rsc-v1-0-b223bd2ac8dd@linaro.org

> +			interconnect-names = "mdp0-mem",
> +					     "mdp1-mem",
> +					     "cpu-cfg";
>  
>  			resets = <&dispcc DISP_CC_MDSS_CORE_BCR>;
>