[Intel-gfx] [PATCH 2/2] drm/i915: Extend hotplug detect retry on TypeC connectors to 5 seconds

[Imre Deak]

On TypeC ports if a sink deasserts/reasserts its HPD signal, generating
a hotplug interrupt without the sink getting unplugged/replugged from
the connector, there can be an up to 3 seconds delay until the AUX
channel gets functional. To avoid detection failures this delay causes
retry the detection for 5 seconds.

I noticed this on ICL/TGL RVPs and a DELL XPS 13 7390 ICL laptop.

References: https://gitlab.freedesktop.org/drm/intel/issues/1067
Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/display/intel_ddi.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index 4f508bf70f3b..2d947ff83488 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -4371,7 +4371,10 @@ static enum intel_hotplug_state
 intel_ddi_hotplug(struct intel_encoder *encoder,
 		  struct intel_connector *connector)
 {
+	struct drm_i915_private *i915 = to_i915(encoder->base.dev);
 	struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
+	enum phy phy = intel_port_to_phy(i915, encoder->port);
+	bool is_tc = intel_phy_is_tc(i915, phy);
 	struct drm_modeset_acquire_ctx ctx;
 	enum intel_hotplug_state state;
 	int ret;
@@ -4414,8 +4417,15 @@ intel_ddi_hotplug(struct intel_encoder *encoder,
 	 * valid EDID. To solve this schedule another detection cycle if this
 	 * time around we didn't detect any change in the sink's connection
 	 * status.
+	 *
+	 * Type-c connectors which get their HPD signal deasserted then
+	 * reasserted, without unplugging/replugging the sink from the
+	 * connector, introduce a delay until the AUX channel communication
+	 * becomes functional. Retry the detection for 5 seconds on type-c
+	 * connectors to account for this delay.
 	 */
-	if (state == INTEL_HOTPLUG_UNCHANGED && !connector->hotplug_retries &&
+	if (state == INTEL_HOTPLUG_UNCHANGED &&
+	    connector->hotplug_retries < (is_tc ? 5 : 1) &&
 	    !dig_port->dp.is_mst)
 		state = INTEL_HOTPLUG_RETRY;
 
-- 
2.23.1