drm/i915: tune down the fast link training vs boot fail

commit 2c57b18a upstream.

It's been unfixed since a while and no one is immediately working on
this. And we have the FIXME already. And now also a task in the DP
team's backlog.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
References: https://lists.freedesktop.org/archives/intel-gfx/2016-July/101951.htmlAcked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[danvet: Adjust comment per Ville's feedback.]
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161213195414.28923-1-daniel.vetter@ffwll.chSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

(cherry picked from commit 2dd85aeb)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_dp.c

@@ -4019,8 +4019,8 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
 		return;
 
 	/* FIXME: we need to synchronize this sort of stuff with hardware
-	 * readout */
-	if (WARN_ON_ONCE(!intel_dp->lane_count))
+	 * readout. Currently fast link training doesn't work on boot-up. */
+	if (!intel_dp->lane_count)
 		return;
 
 	/* if link training is requested we should perform it always */