[PATCH 4.18 161/171] drm/i915/dp: Restrict link retrain workaround to external monitors

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>

commit f9776280c29e77a18cbc7ebb6d48f7885e494990 upstream.

Commit '3cf71bc9904d ("drm/i915: Re-apply "Perform link quality check,
unconditionally during long pulse"")' applies a work around for sinks
that don't signal link loss. The work around does not need to have to be
that broad as the issue was seen with only one particular monitor; limit
this only for external displays as eDP features like PSR turn off the link
and the driver ends up retraining the link seeeing that link is not
synchronized.

Cc: Lyude Paul <lyude@xxxxxxxxxx>
Cc: Jan-Marek Glogowski <glogow@xxxxxxxxxx>
Cc: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
References: 3cf71bc9904d ("drm/i915: Re-apply "Perform link quality check, unconditionally during long pulse"")
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
Reviewed-by: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20180927205735.16651-2-dhinakaran.pandiyan@xxxxxxxxx
(cherry picked from commit f24f6eb95807bca0dbd8dc5b2f3a4099000f4472)
Fixes: 399334708b4f ("drm/i915: Re-apply "Perform link quality check, unconditionally during long pulse"")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/i915/intel_dp.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4872,12 +4872,13 @@ intel_dp_long_pulse(struct intel_connect
 		 */
 		status = connector_status_disconnected;
 		goto out;
-	} else {
-		/*
-		 * Some external monitors do not signal loss of link
-		 * synchronization with an IRQ_HPD, so force a link status
-		 * check.
-		 */
+	}
+
+	/*
+	 * Some external monitors do not signal loss of link synchronization
+	 * with an IRQ_HPD, so force a link status check.
+	 */
+	if (!intel_dp_is_edp(intel_dp)) {
 		struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
 
 		intel_dp_retrain_link(encoder, ctx);