drm/i915/xe3: Restrict PTL intel_encoder_is_c10phy() to only PHY A

On PTL, no combo PHY is connected to PORT B. However, PORT B can
still be used for Type-C and will utilize the C20 PHY for eDP
over Type-C. In such configurations, VBTs also enumerate PORT B.

This leads to issues where PORT B is incorrectly identified as using the
C10 PHY, due to the assumption that returning true for PORT B in
intel_encoder_is_c10phy() would not cause problems.

From PTL's perspective, only PORT A/PHY A uses the C10 PHY.

Update the helper intel_encoder_is_c10phy() to return true only for
PORT A/PHY on PTL.

v2: Change the condition code style for ptl/wcl

Bspec: 72571,73944
Fixes: 9d10de78a37f ("drm/i915/wcl: C10 phy connected to port A and B")
Signed-off-by: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://lore.kernel.org/r/20250922150317.2334680-4-dnyaneshwar.bhadane@intel.com

1 files changed, 6 insertions, 8 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_cx0_phy.c b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
index 801235a5bc0a..a2d2cecf7121 100644
--- a/drivers/gpu/drm/i915/display/intel_cx0_phy.c
+++ b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
@@ -39,14 +39,12 @@ bool intel_encoder_is_c10phy(struct intel_encoder *encoder)
 	struct intel_display *display = to_intel_display(encoder);
 	enum phy phy = intel_encoder_to_phy(encoder);
 
-	/* PTL doesn't have a PHY connected to PORT B; as such,
-	 * there will never be a case where PTL uses PHY B.
-	 * WCL uses PORT A and B with the C10 PHY.
-	 * Reusing the condition for WCL and extending it for PORT B
-	 * should not cause any issues for PTL.
-	 */
-	if (display->platform.pantherlake && phy < PHY_C)
-		return true;
+	if (display->platform.pantherlake) {
+		if (display->platform.pantherlake_wildcatlake)
+			return phy <= PHY_B;
+		else
+			return phy == PHY_A;
+	}
 
 	if ((display->platform.lunarlake || display->platform.meteorlake) && phy < PHY_C)
 		return true;