drm/i915/dsi: fix dual-link DSI backlight and CABC ports for display 11+

The VBT dual-link DSI backlight and CABC still use ports A and C, both
in Bspec and code, while display 11+ DSI only supports ports A and
B. Assume port C actually means port B for display 11+ when parsing VBT.

Bspec: 20154
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6476
Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/8c462718bcc7b36a83e09d0a5eef058b6bc8b1a2.1660664162.git.jani.nikula@intel.com

drivers/gpu/drm/i915/display/intel_bios.c

@@ -1596,6 +1596,8 @@ static void parse_dsi_backlight_ports(struct drm_i915_private *i915,
 				      struct intel_panel *panel,
 				      enum port port)
 {
+	enum port port_bc = DISPLAY_VER(i915) >= 11 ? PORT_B : PORT_C;
+
 	if (!panel->vbt.dsi.config->dual_link || i915->vbt.version < 197) {
 		panel->vbt.dsi.bl_ports = BIT(port);
 		if (panel->vbt.dsi.config->cabc_supported)
@@ -1609,11 +1611,11 @@ static void parse_dsi_backlight_ports(struct drm_i915_private *i915,
 		panel->vbt.dsi.bl_ports = BIT(PORT_A);
 		break;
 	case DL_DCS_PORT_C:
-		panel->vbt.dsi.bl_ports = BIT(PORT_C);
+		panel->vbt.dsi.bl_ports = BIT(port_bc);
 		break;
 	default:
 	case DL_DCS_PORT_A_AND_C:
-		panel->vbt.dsi.bl_ports = BIT(PORT_A) | BIT(PORT_C);
+		panel->vbt.dsi.bl_ports = BIT(PORT_A) | BIT(port_bc);
 		break;
 	}
 
@@ -1625,12 +1627,12 @@ static void parse_dsi_backlight_ports(struct drm_i915_private *i915,
 		panel->vbt.dsi.cabc_ports = BIT(PORT_A);
 		break;
 	case DL_DCS_PORT_C:
-		panel->vbt.dsi.cabc_ports = BIT(PORT_C);
+		panel->vbt.dsi.cabc_ports = BIT(port_bc);
 		break;
 	default:
 	case DL_DCS_PORT_A_AND_C:
 		panel->vbt.dsi.cabc_ports =
-					BIT(PORT_A) | BIT(PORT_C);
+					BIT(PORT_A) | BIT(port_bc);
 		break;
 	}
 }