[PATCH v5 1/2] dt-bindings: display: bridge: cdns,mhdp8546: Add no-hpd property to the cadence bridge

[Yashas D]

From: Rahul T R <r-ravikumar@xxxxxx>

The mhdp bridge can work without its HPD pin hooked up to the connector,
but the current bridge driver throws an error when hpd line is not
connected to the connector. For such cases, we need an indication for
no-hpd, using which we can bypass the hpd detection and instead use the
auxiliary channels connected to the DP connector to confirm the
connection.
So add no-hpd property to the bindings, to disable hpd when not
connected or cannot be used for hotplug detection.

Signed-off-by: Rahul T R <r-ravikumar@xxxxxx>
Signed-off-by: Jayesh Choudhary <j-choudhary@xxxxxx>
Signed-off-by: Yashas D <y-d@xxxxxx>
---
 .../bindings/display/bridge/cdns,mhdp8546.yaml  | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
index c2b369456e4e..f19a4900ecd8 100644
--- a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
@@ -57,6 +57,23 @@ properties:
   interrupts:
     maxItems: 1
 
+  no-hpd:
+    type: boolean
+    description:
+      Set if the HPD line on the bridge isn't physically connected to the
+      DisplayPort connector or cannot be used for hotplug detection.
+
+      Valid use cases include:
+      - HPD pin not routed to the connector on the PCB
+      - HPD signal muxed with another function (e.g., audio) on the SoC,
+        making it unavailable for hotplug detection
+      - Hardware design where HPD cannot reliably detect monitor presence
+
+      When this property is set, the driver will use auxiliary channel (AUX)
+      DPCD reads to detect monitor connection instead of relying on the
+      hardware HPD signal. Monitor detection will use polling rather than
+      interrupt-driven detection.
+
   ports:
     $ref: /schemas/graph.yaml#/properties/ports
 
-- 
2.34.1