drm/i915/dp: add lane_count check in intel_dp_check_link_status
authorMatthew Auld <matthew.auld@intel.com>
Wed, 19 Oct 2016 21:29:53 +0000 (22:29 +0100)
committerVille Syrjälä <ville.syrjala@linux.intel.com>
Fri, 21 Oct 2016 13:09:22 +0000 (16:09 +0300)
commitd4cb3fd9b548b8bfe2a712ec920b9ebabd3547ab
treec2e9462d4d5b74c8cafec6174dd0de81affaa04e
parentc8a89b08a43e640f5ea5dcc4b59f7cea79c890a2
drm/i915/dp: add lane_count check in intel_dp_check_link_status

Currently it's entirely possible to go through the link training step
without first determining the lane_count, which is silly since we end up
doing a bunch of aux transfers of size = 0, as highlighted by
WARN_ON(!msg->buffer != !msg->size), and can only ever result in a
'failed to update link training' message. This can be observed during
intel_dp_long_pulse where we can do the link training step, but before
we have had a chance to set the link params. To avoid this we add an
extra check for the lane_count in intel_dp_check_link_status, which
should prevent us from doing the link training step prematurely.

v2: add WARN_ON_ONCE and FIXME comment (Ville)

References: https://bugs.freedesktop.org/show_bug.cgi?id=97344
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1476912593-10019-1-git-send-email-matthew.auld@intel.com
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
drivers/gpu/drm/i915/intel_dp.c