[PATCH v2 3/5] dt-bindings: phy: qcom,sc8280xp-qmp-usb43dp-phy: Document static lanes mapping

[Dmitry Baryshkov]

On Tue, Sep 02, 2025 at 11:35:25AM +0200, Neil Armstrong wrote:
> On 02/09/2025 11:30, Dmitry Baryshkov wrote:
> > On Tue, Sep 02, 2025 at 11:00:30AM +0200, Neil Armstrong wrote:
> > > The QMP USB3/DP Combo PHY hosts an USB3 phy and a DP PHY on top
> > > of a combo glue to route either lanes to the 4 shared physical lanes.
> > > 
> > > The routing of the lanes can be:
> > > - 2 DP + 2 USB3
> > > - 4 DP
> > > - 2 USB3
> > > 
> > > The layout of the lanes was designed to be mapped and swapped
> > > related to the USB-C Power Delivery negociation, so it supports
> > > a finite set of mappings inherited by the USB-C Altmode layouts.
> > > 
> > > Nevertheless those QMP Comby PHY can be statically used to
> > > drive a DisplayPort connector, DP->HDMI bridge, USB3 A Connector,
> > > etc... without an USB-C connector and no PD events.
> > > 
> > > Add a property that documents the static lanes mapping to
> > > each underlying PHY to allow supporting boards directly
> > > connecting USB3 and DisplayPort lanes to the QMP Combo
> > > lanes.
> > > 
> > > Signed-off-by: Neil Armstrong <neil.armstrong at linaro.org>
> > > ---
> > >   .../phy/qcom,sc8280xp-qmp-usb43dp-phy.yaml         | 29 ++++++++++++++++++++++
> > >   1 file changed, 29 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb43dp-phy.yaml b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb43dp-phy.yaml
> > > index c8bc512df08b5694c8599f475de78679a4438449..12511a462bc6245e0b82726d053d8605148c5047 100644
> > > --- a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb43dp-phy.yaml
> > > +++ b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb43dp-phy.yaml
> > > @@ -76,6 +76,35 @@ properties:
> > >     mode-switch: true
> > >     orientation-switch: true
> > > +  qcom,static-lanes-mapping:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32-array
> > > +    minItems: 4
> > > +    items:
> > > +      enum:
> > > +        - 0 # Unconnected (PHY_NONE)
> > > +        - 4 # USB3 (PHY_TYPE_USB3)
> > > +        - 6 # DisplayPort (PHY_TYPE_DP)
> > > +    description:
> > > +      Describes the static mapping of the Combo PHY lanes, when not used
> > > +      a in a Type-C dynamic setup using USB-C PD Events to change the mapping.
> > > +      The 4 lanes can either routed to the underlying DP PHY or the USB3 PHY.
> > > +      Only 2 of the lanes can be connected to the USB3 PHY, but the 4 lanes can
> > > +      be connected to the DP PHY.
> > 
> > It feels like this significantly duplicates existing data-lanes
> > definitions. Can we use that property to express the same semantics?
> 
> Well yes it has the same semantics, but not really the same meaning. data-lanes is designed
> to describes the lanes layout/ordering, not the type/mapping.
> 
> Here, we do not describe the ordering, i.e which source lane is connected to which endpoint splot,
> but which lane is supposed to connect to which internal PHY.
> 
> Anyway, I'm open to suggestions.

phy at abcdef {
	ports {
		port at 1 {
			endpoint {
				remote-endpoint = <&&usb_1_dwc3_ss>;
				data-lanes = <2 3>;
			};
		};

		port at 2 {
			endpoint {
				remote-endpoint = <&mdss_dp0_out>;
				data-lanes = <1>;
			};
		};
	};
};

phy at cafecafe {
	ports {
		port at 1 {
			endpoint {
				remote-endpoint = <&&usb_1_dwc3_ss>;
				status = "disabled";
			};
		};

		port at 2 {
			endpoint {
				remote-endpoint = <&mdss_dp0_out>;
				data-lanes = <2 3 0 1>;
			};
		};
	};
};


> 
> Neil
> 
> > 
> > 
> > > +      The numbers corresponds to the PHY Type the lanes are connected to.
> > > +      The possible combinations are
> > > +        <0 0 0 0> when none are connected
> > > +        <4 4 0 6> USB3 and DP single lane
> > > +        <4 4 6 6> USB3 and DP
> > > +        <6 6 4 4> DP and USB3
> > > +        <6 0 4 4> DP and USB3 single lane
> > > +        <4 4 0 0> USB3 Only
> > > +        <0 0 4 4> USB3 Only
> > > +        <6 0 0 0> DP single lane
> > > +        <0 0 0 6> DP single lane
> > > +        <6 6 0 0> DP 2 lanes
> > > +        <0 0 6 6> DP 2 lanes
> > > +        <6 6 6 6> DP 4 lanes
> > > +
> > >     ports:
> > >       $ref: /schemas/graph.yaml#/properties/ports
> > >       properties:
> > > 
> > > -- 
> > > 2.34.1
> > > 
> > 
> 

-- 
With best wishes
Dmitry