From 3f88f2431c8289ae98319daad16367b1420e9d53 Mon Sep 17 00:00:00 2001
From: Imre Deak <imre.deak@intel.com>
Date: Mon, 18 Oct 2021 12:41:52 +0300
Subject: drm/i915/dp: Ensure sink/link max lane count values are always valid
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Git-commit: bedcaddadd22da82fc2590569ff81a31045176b1
Patch-mainline: v5.17-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

Print an error if the DPCD sink max lane count is invalid and fix it up.

While at it also add an assert that the link max lane count (derived
from intel_dp_max_common_lane_count(), potentially reduced by the LT
fallback logic) value is also valid.

Cc: Ville Syrj채l채 <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrj채l채 <ville.syrjala@linux.intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211018094154.1407705-5-imre.deak@intel.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 .../drm/i915/display/intel_display_types.h    |  2 +
 drivers/gpu/drm/i915/display/intel_dp.c       | 44 ++++++++++++++++++-
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index aa7238245b0e..c097b29b414c 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1563,6 +1563,8 @@ struct intel_dp {
 	int num_sink_rates;
 	int sink_rates[DP_MAX_SUPPORTED_RATES];
 	bool use_rate_select;
+	/* Max sink lane count as reported by DP_MAX_LANE_COUNT */
+	int max_sink_lane_count;
 	/* intersection of source and sink rates */
 	int num_common_rates;
 	int common_rates[DP_MAX_SUPPORTED_RATES];
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 2ea3ff600089..bc4d73d54930 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -198,6 +198,35 @@ static void intel_dp_set_sink_rates(struct intel_dp *intel_dp)
 	intel_dp->num_sink_rates = i;
 }
 
+static void intel_dp_set_default_max_sink_lane_count(struct intel_dp *intel_dp)
+{
+	intel_dp->max_sink_lane_count = 1;
+}
+
+static void intel_dp_set_max_sink_lane_count(struct intel_dp *intel_dp)
+{
+	struct intel_connector *connector = intel_dp->attached_connector;
+	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+	struct intel_encoder *encoder = &intel_dig_port->base;
+
+	intel_dp->max_sink_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
+
+	switch (intel_dp->max_sink_lane_count) {
+	case 1:
+	case 2:
+	case 4:
+		return;
+	}
+
+	drm_err(&dp_to_i915(intel_dp)->drm,
+		"[CONNECTOR:%d:%s][ENCODER:%d:%s] Invalid DPCD max lane count (%d), using default\n",
+		connector->base.base.id, connector->base.name,
+		encoder->base.base.id, encoder->base.name,
+		intel_dp->max_sink_lane_count);
+
+	intel_dp_set_default_max_sink_lane_count(intel_dp);
+}
+
 /* Get length of rates array potentially limited by max_rate. */
 static int intel_dp_rate_limit_len(const int *rates, int len, int max_rate)
 {
@@ -231,7 +260,7 @@ static int intel_dp_max_common_lane_count(struct intel_dp *intel_dp)
 {
 	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
 	int source_max = dig_port->max_lanes;
-	int sink_max = drm_dp_max_lane_count(intel_dp->dpcd);
+	int sink_max = intel_dp->max_sink_lane_count;
 	int fia_max = intel_tc_port_fia_max_lane_count(dig_port);
 	int lttpr_max = drm_dp_lttpr_max_lane_count(intel_dp->lttpr_common_caps);
 
@@ -243,7 +272,15 @@ static int intel_dp_max_common_lane_count(struct intel_dp *intel_dp)
 
 int intel_dp_max_lane_count(struct intel_dp *intel_dp)
 {
-	return intel_dp->max_link_lane_count;
+	switch (intel_dp->max_link_lane_count) {
+	case 1:
+	case 2:
+	case 4:
+		return intel_dp->max_link_lane_count;
+	default:
+		MISSING_CASE(intel_dp->max_link_lane_count);
+		return 1;
+	}
 }
 
 /*
@@ -2614,6 +2651,7 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
 		intel_dp->use_rate_select = true;
 	else
 		intel_dp_set_sink_rates(intel_dp);
+	intel_dp_set_max_sink_lane_count(intel_dp);
 
 	intel_dp_set_common_rates(intel_dp);
 	intel_dp_reset_max_link_params(intel_dp);
@@ -2659,6 +2697,7 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 				 drm_dp_is_branch(intel_dp->dpcd));
 
 		intel_dp_set_sink_rates(intel_dp);
+		intel_dp_set_max_sink_lane_count(intel_dp);
 		intel_dp_set_common_rates(intel_dp);
 	}
 
@@ -5025,6 +5064,7 @@ intel_dp_init_connector(struct intel_digital_port *dig_port,
 
 	intel_dp_set_source_rates(intel_dp);
 	intel_dp_set_default_sink_rates(intel_dp);
+	intel_dp_set_default_max_sink_lane_count(intel_dp);
 	intel_dp_set_common_rates(intel_dp);
 	intel_dp_reset_max_link_params(intel_dp);
 
-- 
2.38.1