Re: [PATCH v2 3/3] arm64: dts: qcom: sm8750: describe all MDSS block resets

[Dmitry Baryshkov]

On Thu, Oct 29, 2026 at 08:32:38PM +0800, Qianhui Xu wrote:
> The SM8750 display clock controller provides, beside the MDSS core
> reset, block resets for the MDSS core INT2 interrupt controller and for
> the MDSS RSC.  On devices whose bootloader hands over with the display
> block still active (PLLs locked, MDSS core / INT2 / RSC out of reset),
> the kernel so far reset only the MDSS core and left the INT2 and RSC
> blocks in the state left behind by the bootloader; command-mode panel
> initialisation then fails with command DMA timeouts and the display
> comes up as backlight only, without a DRM device.
> 
> Describe all three block resets so that the MDSS reset returns the
> whole display subsystem to a known state before any display hardware is
> programmed.
> 
> The reset runs after the display clock controller has programmed its
> PLLs (the clock controller supplies the MDSS clocks and power domain,
> so it always probes first).  The block resets do not touch the PLL
> registers and no display pipeline is active at this point, so the PLL
> configuration survives the reset and nothing visible can glitch.
> 
> Signed-off-by: Qianhui Xu <xiaqinghuan@xxxxxxxxxxxxxxxx>
> ---
>  arch/arm64/boot/dts/qcom/sm8750.dtsi | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sm8750.dtsi b/arch/arm64/boot/dts/qcom/sm8750.dtsi
> index dd738d13df..950c528bc4 100644
> --- a/arch/arm64/boot/dts/qcom/sm8750.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sm8750.dtsi
> @@ -3071,7 +3071,9 @@ mdss: display-subsystem@ae00000 {
>  				 <&gcc GCC_DISP_HF_AXI_CLK>,
>  				 <&dispcc DISP_CC_MDSS_MDP_CLK>;
>  
> -			resets = <&dispcc DISP_CC_MDSS_CORE_BCR>;
> +			resets = <&dispcc DISP_CC_MDSS_CORE_BCR>,
> +				 <&dispcc DISP_CC_MDSS_CORE_INT2_BCR>,
> +				 <&dispcc DISP_CC_MDSS_RSCC_BCR>;

Please drop the RSCC reset

>  
>  			interconnects = <&mmss_noc MASTER_MDP QCOM_ICC_TAG_ALWAYS
>  					 &mc_virt SLAVE_EBI1 QCOM_ICC_TAG_ALWAYS>,
> -- 
> 2.53.0
> 

-- 
With best wishes
Dmitry