[PATCH RFC 1/3] dt-bindings: phy: qcom,sc8280xp-qmp-usb43dp-phy: Document default phy mode

[Neil Armstrong]

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

And the layout of the lanes can be swpped depending of an
eventual USB-C connector orientation.

Nevertheless those QMP Comby PHY can be statically used to
drive a DisplayPort connector, DP->HDMI bridge, USB3 A Connector...

But if a 4lanes DP->HDMI bridge is directly connected to the
QMP Comby PHY lanes, in the default routing 2 or the 4 lanes would
probbaly be USB3, making the DP->HDMI bridge non functional.

Add a property to hint in which layout mode the QMP Comby PHY
should be as startup.

Signed-off-by: Neil Armstrong <neil.armstrong at linaro.org>
---
 .../bindings/phy/qcom,sc8280xp-qmp-usb43dp-phy.yaml         | 13 +++++++++++++
 1 file changed, 13 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..129475a1d9527733e43ded5a38aad766f9810fe7 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 +76,19 @@ properties:
   mode-switch: true
   orientation-switch: true
 
+  qcom,combo-initial-mode:
+    description:
+      Describe the initial mode of the Combo PHY configuration.
+      The Combo PHY is a wrapper on top of a DP PHY and an USB3 PHY,
+      sharing the same SuperSpeed lanes with either DisplayPort over
+      the 4 lanes (dp), USB3 on a pair of lanes (usb3) or both
+      technologies in a 2+2 configuration (usb3+dp) as default.
+    default: usb3+dp
+    enum:
+      - usb3+dp
+      - usb3
+      - dp
+
   ports:
     $ref: /schemas/graph.yaml#/properties/ports
     properties:

-- 
2.34.1