drm/i915/tc: Catch TC users accessing FIA registers without enable aux

As described in "drm/i915/tc/icl: Implement TC cold sequences" users
of TC functions should held aux power well during access to avoid
read garbage due HW in TC cold state.

v3:
- renamed is_tc_cold_blocked() to assert_tc_cold_blocked()
- restored the removed 0xffffffff checks
Reviewed-by: Imre Deak <imre.deak@intel.com>
Tested-by: You-Sheng Yang <vicamo.yang@canonical.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200414194956.164323-7-jose.souza@intel.com

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

@@ -95,6 +95,20 @@ tc_cold_unblock(struct intel_digital_port *dig_port, intel_wakeref_t wakeref)
 	intel_display_power_put_async(i915, domain, wakeref);
 }
 
+static void
+assert_tc_cold_blocked(struct intel_digital_port *dig_port)
+{
+	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
+	bool enabled;
+
+	if (INTEL_GEN(i915) == 11 && !dig_port->tc_legacy_port)
+		return;
+
+	enabled = intel_display_power_is_enabled(i915,
+						 tc_cold_get_power_domain(dig_port));
+	drm_WARN_ON(&i915->drm, !enabled);
+}
+
 u32 intel_tc_port_get_lane_mask(struct intel_digital_port *dig_port)
 {
 	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
@@ -105,6 +119,7 @@ u32 intel_tc_port_get_lane_mask(struct intel_digital_port *dig_port)
 				      PORT_TX_DFLEXDPSP(dig_port->tc_phy_fia));
 
 	drm_WARN_ON(&i915->drm, lane_mask == 0xffffffff);
+	assert_tc_cold_blocked(dig_port);
 
 	lane_mask &= DP_LANE_ASSIGNMENT_MASK(dig_port->tc_phy_fia_idx);
 	return lane_mask >> DP_LANE_ASSIGNMENT_SHIFT(dig_port->tc_phy_fia_idx);
@@ -120,6 +135,7 @@ u32 intel_tc_port_get_pin_assignment_mask(struct intel_digital_port *dig_port)
 				     PORT_TX_DFLEXPA1(dig_port->tc_phy_fia));
 
 	drm_WARN_ON(&i915->drm, pin_mask == 0xffffffff);
+	assert_tc_cold_blocked(dig_port);
 
 	return (pin_mask & DP_PIN_ASSIGNMENT_MASK(dig_port->tc_phy_fia_idx)) >>
 	       DP_PIN_ASSIGNMENT_SHIFT(dig_port->tc_phy_fia_idx);
@@ -134,6 +150,8 @@ int intel_tc_port_fia_max_lane_count(struct intel_digital_port *dig_port)
 	if (dig_port->tc_mode != TC_PORT_DP_ALT)
 		return 4;
 
+	assert_tc_cold_blocked(dig_port);
+
 	lane_mask = 0;
 	with_intel_display_power(i915, POWER_DOMAIN_DISPLAY_CORE, wakeref)
 		lane_mask = intel_tc_port_get_lane_mask(dig_port);
@@ -166,6 +184,8 @@ void intel_tc_port_set_fia_lane_count(struct intel_digital_port *dig_port,
 	drm_WARN_ON(&i915->drm,
 		    lane_reversal && dig_port->tc_mode != TC_PORT_LEGACY);
 
+	assert_tc_cold_blocked(dig_port);
+
 	val = intel_uncore_read(uncore,
 				PORT_TX_DFLEXDPMLE1(dig_port->tc_phy_fia));
 	val &= ~DFLEXDPMLE1_DPMLETC_MASK(dig_port->tc_phy_fia_idx);