drm/i915/display: Handle dedicated external ports in intel_encoder_is_tc()

Starting with Xe3p_LPD, the VBT has a new field, called in the driver
"dedicated_external", which tells that a Type-C capable port is
physically connected to a PHY outside of the Type-C subsystem.  When
that's the case, the driver must not do the extra Type-C programming for
that port.  Update intel_encoder_is_tc() to check for that case.

While at it, add a note to intel_phy_is_tc() to remind us that it is
about whether the respective port is a Type-C capable port rather than
the PHY itself.

(Maybe it would be a nice idea to rename intel_phy_is_tc()?)

Note that this was handled with a new bool member added to struct
intel_digital_port instead of having querying the VBT directly because
VBT memory is freed (intel_bios_driver_remove) before encoder cleanup
(intel_ddi_encoder_destroy), which would cause an oops to happen when
the latter calls intel_encoder_is_tc().  This could be fixed by keeping
VBT data around longer, but that's left for a follow-up work, if deemed
necessary.

v2:
  - Drop printing info about dedicated external, now that we are doing
    it when parsing the VBT. (Jani)
  - Add a FIXME comment on the code explaining why we need to store
    dedicated_external in struct intel_digital_port. (Jani)
v3:
  - Simplify the code by using NULL check for dig_port to avoid using
    intel_encoder_is_dig_port(). (Imre)

Cc: Imre Deak <imre.deak@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Shekhar Chauhan <shekhar.chauhan@intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20251202012306.9315-4-matthew.s.atwood@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>

3 files changed, 27 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index a83a4200e631..cb91d07cdaa6 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -5423,6 +5423,17 @@ void intel_ddi_init(struct intel_display *display,
 			goto err;
 	}
 
+	/*
+	 * FIXME: We currently need to store dedicated_external because devdata
+	 * does not live long enough for when intel_encoder_is_tc() is called on
+	 * the unbind path.  This needs to be fixed by making sure that the VBT
+	 * data is kept long enough, so that
+	 * intel_bios_encoder_is_dedicated_external() can be called directly
+	 * from intel_encoder_is_tc().
+	 */
+	if (intel_bios_encoder_is_dedicated_external(devdata))
+		dig_port->dedicated_external = true;
+
 	if (intel_encoder_is_tc(encoder)) {
 		bool is_legacy =
 			!intel_bios_encoder_supports_typec_usb(devdata) &&
diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 5563ff7ee10e..de8ae14e06cd 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -1810,7 +1810,17 @@ bool intel_phy_is_combo(struct intel_display *display, enum phy phy)
 		return false;
 }
 
-/* Prefer intel_encoder_is_tc() */
+/*
+ * This function returns true if the DDI port respective to the PHY enumeration
+ * is a Type-C capable port.
+ *
+ * Depending on the VBT, the port might be configured
+ * as a "dedicated external" port, meaning that actual physical PHY is outside
+ * of the Type-C subsystem and, as such, not really a "Type-C PHY".
+ *
+ * Prefer intel_encoder_is_tc(), especially if you really need to know if we
+ * are dealing with Type-C connections.
+ */
 bool intel_phy_is_tc(struct intel_display *display, enum phy phy)
 {
 	/*
@@ -1909,6 +1919,10 @@ bool intel_encoder_is_snps(struct intel_encoder *encoder)
 bool intel_encoder_is_tc(struct intel_encoder *encoder)
 {
 	struct intel_display *display = to_intel_display(encoder);
+	struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
+
+	if (dig_port && dig_port->dedicated_external)
+		return false;
 
 	return intel_phy_is_tc(display, intel_encoder_to_phy(encoder));
 }
diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index ed0f7448e6cd..f8f7bc956214 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1936,6 +1936,7 @@ struct intel_digital_port {
 	bool lane_reversal;
 	bool ddi_a_4_lanes;
 	bool release_cl2_override;
+	bool dedicated_external;
 	u8 max_lanes;
 	/* Used for DP and ICL+ TypeC/DP and TypeC/HDMI ports. */
 	enum aux_ch aux_ch;