linux-kernel - Re: [PATCH v8 9/9] arm64: dts: qcom: Add MST pixel streams for displayport

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Message-ID: <rfhqfbx4q3kl35ktzaexjjshzosv4a2tkjthtvo24aoisrdvj7@i63a55qx4mnn>
Date: Wed, 3 Sep 2025 16:58:30 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Abel Vesa <abel.vesa@...aro.org>, Mahadevan <quic_mahap@...cinc.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH v8 9/9] arm64: dts: qcom: Add MST pixel streams for
 displayport

On Wed, Sep 03, 2025 at 03:41:45PM +0200, Konrad Dybcio wrote:
> On 9/3/25 1:58 PM, Dmitry Baryshkov wrote:
> > From: Jessica Zhang <jessica.zhang@....qualcomm.com>
> > 
> > Update Qualcomm DT files in order to declare extra stream pixel clocks
> > and extra register resources used on these platforms to support
> > DisplayPort MST.
> > 
> > The driver will continue to work with the old DTS files as even after
> > adding MST support the driver will have to support old DTS files which
> > didn't have MST clocks.
> > 
> > Signed-off-by: Jessica Zhang <jessica.zhang@....qualcomm.com>
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
> > ---
> 
> [...]
> 
> > diff --git a/arch/arm64/boot/dts/qcom/sc8180x.dtsi b/arch/arm64/boot/dts/qcom/sc8180x.dtsi
> > index 70c87c79e1325f4ab4c81f34e99c0b52be4b3810..e6a7248040095077d6f98d632f4e8a1868432445 100644
> > --- a/arch/arm64/boot/dts/qcom/sc8180x.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/sc8180x.dtsi
> > @@ -3241,16 +3241,20 @@ mdss_dp0: displayport-controller@...0000 {
> >  					 <&dispcc DISP_CC_MDSS_DP_AUX_CLK>,
> >  					 <&dispcc DISP_CC_MDSS_DP_LINK_CLK>,
> >  					 <&dispcc DISP_CC_MDSS_DP_LINK_INTF_CLK>,
> > -					 <&dispcc DISP_CC_MDSS_DP_PIXEL_CLK>;
> > +					 <&dispcc DISP_CC_MDSS_DP_PIXEL_CLK>,
> > +					 <&dispcc DISP_CC_MDSS_DP_PIXEL1_CLK>;
> >  				clock-names = "core_iface",
> >  					      "core_aux",
> >  					      "ctrl_link",
> >  					      "ctrl_link_iface",
> > -					      "stream_pixel";
> > +					      "stream_pixel",
> > +					      "stream_1_pixel";
> >  
> >  				assigned-clocks = <&dispcc DISP_CC_MDSS_DP_LINK_CLK_SRC>,
> > -						  <&dispcc DISP_CC_MDSS_DP_PIXEL_CLK_SRC>;
> > +						  <&dispcc DISP_CC_MDSS_DP_PIXEL_CLK_SRC>,
> > +						  <&dispcc DISP_CC_MDSS_DP_PIXEL1_CLK_SRC>;
> >  				assigned-clock-parents = <&usb_prim_qmpphy QMP_USB43DP_DP_LINK_CLK>,
> > +							 <&usb_prim_qmpphy QMP_USB43DP_DP_VCO_DIV_CLK>,
> >  							 <&usb_prim_qmpphy QMP_USB43DP_DP_VCO_DIV_CLK>;
> >  
> >  				phys = <&usb_prim_qmpphy QMP_USB43DP_DP_PHY>;
> > @@ -3319,16 +3323,20 @@ mdss_dp1: displayport-controller@...8000 {
> >  					 <&dispcc DISP_CC_MDSS_DP_AUX1_CLK>,
> >  					 <&dispcc DISP_CC_MDSS_DP_LINK1_CLK>,
> >  					 <&dispcc DISP_CC_MDSS_DP_LINK1_INTF_CLK>,
> > -					 <&dispcc DISP_CC_MDSS_DP_PIXEL2_CLK>;
> > +					 <&dispcc DISP_CC_MDSS_DP_PIXEL2_CLK>,
> > +					 <&dispcc DISP_CC_MDSS_DP_PIXEL1_CLK>;
> >  				clock-names = "core_iface",
> >  					      "core_aux",
> >  					      "ctrl_link",
> >  					      "ctrl_link_iface",
> > -					      "stream_pixel";
> > +					      "stream_pixel",
> > +					      "stream_1_pixel";
> >  
> >  				assigned-clocks = <&dispcc DISP_CC_MDSS_DP_LINK1_CLK_SRC>,
> > -						  <&dispcc DISP_CC_MDSS_DP_PIXEL2_CLK_SRC>;
> > +						  <&dispcc DISP_CC_MDSS_DP_PIXEL2_CLK_SRC>,
> > +						  <&dispcc DISP_CC_MDSS_DP_PIXEL1_CLK_SRC>;
> >  				assigned-clock-parents = <&usb_sec_qmpphy QMP_USB43DP_DP_LINK_CLK>,
> > +							 <&usb_sec_qmpphy QMP_USB43DP_DP_VCO_DIV_CLK>,
> >  							 <&usb_sec_qmpphy QMP_USB43DP_DP_VCO_DIV_CLK>;
> 
> Something's not right here

No, it's correct as far as I understand. On this platform INTF3 / PIXEL1
is shared between INTF0 / PIXEL and INTF4 / PIXEL2. So it is
counterintuitive, but seems to be correct.

-- 
With best wishes
Dmitry