drm/i915/xe2lpd: Read pin assignment from IOM

Starting from display version 20, we need to read the pin assignment
from the IOM TCSS_DDI_STATUS register instead of reading it from the
FIA.

We use the pin assignment to decide the maximum lane count.  So, to
support this change, add a new lnl_tc_port_get_max_lane_count() function
that reads from the TCSS_DDI_STATUS register and decides the maximum
lane count based on that.

BSpec: 69594
Cc: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230919192128.2045154-14-lucas.demarchi@intel.com

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

@@ -290,6 +290,31 @@ u32 intel_tc_port_get_pin_assignment_mask(struct intel_digital_port *dig_port)
 	       DP_PIN_ASSIGNMENT_SHIFT(tc->phy_fia_idx);
 }
 
+static int lnl_tc_port_get_max_lane_count(struct intel_digital_port *dig_port)
+{
+	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
+	enum tc_port tc_port = intel_port_to_tc(i915, dig_port->base.port);
+	intel_wakeref_t wakeref;
+	u32 val, pin_assignment;
+
+	with_intel_display_power(i915, POWER_DOMAIN_DISPLAY_CORE, wakeref)
+		val = intel_de_read(i915, TCSS_DDI_STATUS(tc_port));
+
+	pin_assignment =
+		REG_FIELD_GET(TCSS_DDI_STATUS_PIN_ASSIGNMENT_MASK, val);
+
+	switch (pin_assignment) {
+	default:
+		MISSING_CASE(pin_assignment);
+		fallthrough;
+	case DP_PIN_ASSIGNMENT_D:
+		return 2;
+	case DP_PIN_ASSIGNMENT_C:
+	case DP_PIN_ASSIGNMENT_E:
+		return 4;
+	}
+}
+
 static int mtl_tc_port_get_max_lane_count(struct intel_digital_port *dig_port)
 {
 	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
@@ -348,6 +373,9 @@ int intel_tc_port_max_lane_count(struct intel_digital_port *dig_port)
 
 	assert_tc_cold_blocked(tc);
 
+	if (DISPLAY_VER(i915) >= 20)
+		return lnl_tc_port_get_max_lane_count(dig_port);
+
 	if (DISPLAY_VER(i915) >= 14)
 		return mtl_tc_port_get_max_lane_count(dig_port);
 

drivers/gpu/drm/i915/i915_reg.h

@@ -6349,6 +6349,7 @@ enum skl_power_gate {
 #define TCSS_DDI_STATUS(tc)			_MMIO(_PICK_EVEN(tc, \
 								 _TCSS_DDI_STATUS_1, \
 								 _TCSS_DDI_STATUS_2))
+#define  TCSS_DDI_STATUS_PIN_ASSIGNMENT_MASK	REG_GENMASK(28, 25)
 #define  TCSS_DDI_STATUS_READY			REG_BIT(2)
 #define  TCSS_DDI_STATUS_HPD_LIVE_STATUS_TBT	REG_BIT(1)
 #define  TCSS_DDI_STATUS_HPD_LIVE_STATUS_ALT	REG_BIT(0)