drm/i915/dp: Fix link retraining comment in intel_dp_long_pulse()
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: 3cf71bc990
("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-dhinakaran.pandiyan@intel.com
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@ -5074,16 +5074,9 @@ intel_dp_long_pulse(struct intel_connector *connector,
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goto out;
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} else {
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/*
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* If display is now connected check links status,
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* there has been known issues of link loss triggering
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* long pulse.
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*
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* Some sinks (eg. ASUS PB287Q) seem to perform some
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* weird HPD ping pong during modesets. So we can apparently
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* end up with HPD going low during a modeset, and then
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* going back up soon after. And once that happens we must
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* retrain the link to get a picture. That's in case no
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* userspace component reacted to intermittent HPD dip.
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* Some external monitors do not signal loss of link
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* synchronization with an IRQ_HPD, so force a link status
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* check.
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*/
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struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
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