4.18-stable review patch. If anyone has any objections, please let me know.
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From: Dhinakaran Pandiyan dhinakaran.pandiyan@intel.com
commit 49af5d95b9b3c21a84ad115a9db9acbc036d849a upstream.
Comment claims link needs to be retrained because the connected sink raised a long pulse to indicate link loss. If the sink did so, intel_dp_hotplug() would have handled link retraining. Looking at the logs in Bugzilla referenced in commit '3cf71bc9904d ("drm/i915: Re-apply Perform link quality check, unconditionally during long pulse"")', the issue is that the sink does not trigger an interrupt. What we want is ->detect() from user space to check link status and retrain. Ville's review for the original patch also indicates the same root cause. So, rewrite the comment.
v2: Patch split and rewrote comment.
Cc: Lyude Paul lyude@redhat.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Jani Nikula jani.nikula@linux.intel.com Cc: Rodrigo Vivi rodrigo.vivi@intel.com Cc: Jan-Marek Glogowski glogow@fbihome.de References: 3cf71bc9904d ("drm/i915: Re-apply "Perform link quality check, unconditionally during long pulse"") Signed-off-by: Dhinakaran Pandiyan dhinakaran.pandiyan@intel.com Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20180927205735.16651-1-dhinaka... (cherry picked from commit 9ebd8202393dde9d3678c9ec162c1aa63ba17eac) Fixes: 399334708b4f ("drm/i915: Re-apply "Perform link quality check, unconditionally during long pulse"") Cc: stable@vger.kernel.org Signed-off-by: Joonas Lahtinen joonas.lahtinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/gpu/drm/i915/intel_dp.c | 13 +++---------- 1 file changed, 3 insertions(+), 10 deletions(-)
--- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -4874,16 +4874,9 @@ intel_dp_long_pulse(struct intel_connect goto out; } else { /* - * If display is now connected check links status, - * there has been known issues of link loss triggering - * long pulse. - * - * Some sinks (eg. ASUS PB287Q) seem to perform some - * weird HPD ping pong during modesets. So we can apparently - * end up with HPD going low during a modeset, and then - * going back up soon after. And once that happens we must - * retrain the link to get a picture. That's in case no - * userspace component reacted to intermittent HPD dip. + * Some external monitors do not signal loss of link + * synchronization with an IRQ_HPD, so force a link status + * check. */ struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;