tests/kms_atomic_transition: Don't abuse the HSKEW flag to force a modeset

Since kernel commit e995ca0b8139 ("drm/i915: Provide a device level
.mode_valid() hook") i915 will bluntly reject the HSKEW mode flag. Thus
we can't abuse it to force a modeset.

Since we don't particularly care about the visual results here we can
risk making the display unhappy by eg. flipping the hsync polarity
instead.

Also add a comment documenting why we're doing this.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104848
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
1 file changed