[Intel-gfx] [PATCH] drm/i915/dp: Reset link params on connector disconnect

[Manasi Navare]

We have noticed that when link training fails the panel
sends a long pulse indicating connector disconnect. In this case
we need to reset the link parameters instead of continuing
to use the fallback parameters since else this long pulse
by the panel followed by a modeset request which was triggered by the userspace
before getting the connector status as disconnected, will
result into a modeset now using lower link rate/lane count values.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1385
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 28 +++++++++++++++++--------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 55fda074c0ad..f7af372647dd 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -6111,6 +6111,18 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
 	intel_dp->edid_quirks = 0;
 }
 
+static void
+intel_dp_reset_link_params(struct intel_dp *intel_dp)
+{
+	/* Initial max link lane count */
+	intel_dp->max_link_lane_count = intel_dp_max_common_lane_count(intel_dp);
+
+	/* Initial max link rate */
+	intel_dp->max_link_rate = intel_dp_max_common_rate(intel_dp);
+
+	intel_dp->reset_link_params = false;
+}
+
 static int
 intel_dp_detect(struct drm_connector *connector,
 		struct drm_modeset_acquire_ctx *ctx,
@@ -6139,6 +6151,11 @@ intel_dp_detect(struct drm_connector *connector,
 		memset(&intel_dp->compliance, 0, sizeof(intel_dp->compliance));
 		memset(intel_dp->dsc_dpcd, 0, sizeof(intel_dp->dsc_dpcd));
 
+		/*Reset the immutable VRR Capable property */
+		drm_connector_set_vrr_capable_property(connector,
+						       false);
+		intel_dp_reset_link_params(intel_dp);
+
 		if (intel_dp->is_mst) {
 			drm_dbg_kms(&dev_priv->drm,
 				    "MST device may have disappeared %d vs %d\n",
@@ -6152,15 +6169,8 @@ intel_dp_detect(struct drm_connector *connector,
 		goto out;
 	}
 
-	if (intel_dp->reset_link_params) {
-		/* Initial max link lane count */
-		intel_dp->max_link_lane_count = intel_dp_max_common_lane_count(intel_dp);
-
-		/* Initial max link rate */
-		intel_dp->max_link_rate = intel_dp_max_common_rate(intel_dp);
-
-		intel_dp->reset_link_params = false;
-	}
+	if (intel_dp->reset_link_params)
+		intel_dp_reset_link_params(intel_dp);
 
 	intel_dp_print_rates(intel_dp);
 
-- 
2.19.1