drm/i915/icl+/tc: Cache the max lane count value

The PHY's pin assignment value in the TCSS_DDI_STATUS register - as set
by the HW/FW based on the connected DP-alt sink's TypeC/PD pin
assignment negotiation - gets cleared by the HW/FW on LNL+ as soon as
the sink gets disconnected, even if the PHY ownership got acquired
already by the driver (and hence the PHY itself is still connected and
used by the display). This is similar to how the PHY Ready flag gets
cleared on LNL+ in the same register.

To be able to query the max lane count value on LNL+ - which is based on
the above pin assignment - at all times even after the sink gets
disconnected, the max lane count must be determined and cached during
the PHY's HW readout and connect sequences. Do that here, leaving the
actual use of the cached value to a follow-up change.

v2: Don't read out the pin configuration if the PHY is disconnected.

Cc: stable@vger.kernel.org # v6.8+
Reported-by: Charlton Lin <charlton.lin@intel.com>
Tested-by: Khaled Almahallawy <khaled.almahallawy@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://lore.kernel.org/r/20250811080152.906216-3-imre.deak@intel.com

Author: ideak

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

@@ -66,6 +66,7 @@ struct intel_tc_port {
 	enum tc_port_mode init_mode;
 	enum phy_fia phy_fia;
 	u8 phy_fia_idx;
+	u8 max_lane_count;
 };
 
 static enum intel_display_power_domain
@@ -365,12 +366,12 @@ static int intel_tc_port_get_max_lane_count(struct intel_digital_port *dig_port)
 	}
 }
 
-int intel_tc_port_max_lane_count(struct intel_digital_port *dig_port)
+static int get_max_lane_count(struct intel_tc_port *tc)
 {
-	struct intel_display *display = to_intel_display(dig_port);
-	struct intel_tc_port *tc = to_tc_port(dig_port);
+	struct intel_display *display = to_intel_display(tc->dig_port);
+	struct intel_digital_port *dig_port = tc->dig_port;
 
-	if (!intel_encoder_is_tc(&dig_port->base) || tc->mode != TC_PORT_DP_ALT)
+	if (tc->mode != TC_PORT_DP_ALT)
 		return 4;
 
 	assert_tc_cold_blocked(tc);
@@ -384,6 +385,21 @@ int intel_tc_port_max_lane_count(struct intel_digital_port *dig_port)
 	return intel_tc_port_get_max_lane_count(dig_port);
 }
 
+static void read_pin_configuration(struct intel_tc_port *tc)
+{
+	tc->max_lane_count = get_max_lane_count(tc);
+}
+
+int intel_tc_port_max_lane_count(struct intel_digital_port *dig_port)
+{
+	struct intel_tc_port *tc = to_tc_port(dig_port);
+
+	if (!intel_encoder_is_tc(&dig_port->base))
+		return 4;
+
+	return get_max_lane_count(tc);
+}
+
 void intel_tc_port_set_fia_lane_count(struct intel_digital_port *dig_port,
 				      int required_lanes)
 {
@@ -596,9 +612,12 @@ static void icl_tc_phy_get_hw_state(struct intel_tc_port *tc)
 	tc_cold_wref = __tc_cold_block(tc, &domain);
 
 	tc->mode = tc_phy_get_current_mode(tc);
-	if (tc->mode != TC_PORT_DISCONNECTED)
+	if (tc->mode != TC_PORT_DISCONNECTED) {
 		tc->lock_wakeref = tc_cold_block(tc);
 
+		read_pin_configuration(tc);
+	}
+
 	__tc_cold_unblock(tc, domain, tc_cold_wref);
 }
 
@@ -656,8 +675,11 @@ static bool icl_tc_phy_connect(struct intel_tc_port *tc,
 
 	tc->lock_wakeref = tc_cold_block(tc);
 
-	if (tc->mode == TC_PORT_TBT_ALT)
+	if (tc->mode == TC_PORT_TBT_ALT) {
+		read_pin_configuration(tc);
+
 		return true;
+	}
 
 	if ((!tc_phy_is_ready(tc) ||
 	     !icl_tc_phy_take_ownership(tc, true)) &&
@@ -668,6 +690,7 @@ static bool icl_tc_phy_connect(struct intel_tc_port *tc,
 		goto out_unblock_tc_cold;
 	}
 
+	read_pin_configuration(tc);
 
 	if (!tc_phy_verify_legacy_or_dp_alt_mode(tc, required_lanes))
 		goto out_release_phy;
@@ -858,9 +881,12 @@ static void adlp_tc_phy_get_hw_state(struct intel_tc_port *tc)
 	port_wakeref = intel_display_power_get(display, port_power_domain);
 
 	tc->mode = tc_phy_get_current_mode(tc);
-	if (tc->mode != TC_PORT_DISCONNECTED)
+	if (tc->mode != TC_PORT_DISCONNECTED) {
 		tc->lock_wakeref = tc_cold_block(tc);
 
+		read_pin_configuration(tc);
+	}
+
 	intel_display_power_put(display, port_power_domain, port_wakeref);
 }
 
@@ -873,6 +899,9 @@ static bool adlp_tc_phy_connect(struct intel_tc_port *tc, int required_lanes)
 
 	if (tc->mode == TC_PORT_TBT_ALT) {
 		tc->lock_wakeref = tc_cold_block(tc);
+
+		read_pin_configuration(tc);
+
 		return true;
 	}
 
@@ -894,6 +923,8 @@ static bool adlp_tc_phy_connect(struct intel_tc_port *tc, int required_lanes)
 
 	tc->lock_wakeref = tc_cold_block(tc);
 
+	read_pin_configuration(tc);
+
 	if (!tc_phy_verify_legacy_or_dp_alt_mode(tc, required_lanes))
 		goto out_unblock_tc_cold;
 
@@ -1124,9 +1155,12 @@ static void xelpdp_tc_phy_get_hw_state(struct intel_tc_port *tc)
 	tc_cold_wref = __tc_cold_block(tc, &domain);
 
 	tc->mode = tc_phy_get_current_mode(tc);
-	if (tc->mode != TC_PORT_DISCONNECTED)
+	if (tc->mode != TC_PORT_DISCONNECTED) {
 		tc->lock_wakeref = tc_cold_block(tc);
 
+		read_pin_configuration(tc);
+	}
+
 	drm_WARN_ON(display->drm,
 		    (tc->mode == TC_PORT_DP_ALT || tc->mode == TC_PORT_LEGACY) &&
 		    !xelpdp_tc_phy_tcss_power_is_enabled(tc));
@@ -1138,14 +1172,19 @@ static bool xelpdp_tc_phy_connect(struct intel_tc_port *tc, int required_lanes)
 {
 	tc->lock_wakeref = tc_cold_block(tc);
 
-	if (tc->mode == TC_PORT_TBT_ALT)
+	if (tc->mode == TC_PORT_TBT_ALT) {
+		read_pin_configuration(tc);
+
 		return true;
+	}
 
 	if (!xelpdp_tc_phy_enable_tcss_power(tc, true))
 		goto out_unblock_tccold;
 
 	xelpdp_tc_phy_take_ownership(tc, true);
 
+	read_pin_configuration(tc);
+
 	if (!tc_phy_verify_legacy_or_dp_alt_mode(tc, required_lanes))
 		goto out_release_phy;