drm/i915/skl: Don't try to update plane watermarks if they haven't changed
commit ccebc23b upstream. i915 sometimes needs to disable planes in the middle of an atomic commit, and then reenable them later in the same commit. Because of this, we can't make the assumption that the state of the plane actually changed. Since the state of the plane hasn't actually changed, neither have it's watermarks. And if the watermarks hasn't changed then we haven't populated skl_results with anything, which means we'll end up zeroing out a plane's watermarks in the middle of the atomic commit without restoring them later. Simple reproduction recipe: - Get a SKL laptop, launch any kind of X session - Get two extra monitors - Keep hotplugging both displays (so that the display configuration jumps from 1 active pipe to 3 active pipes and back) - Eventually underrun Changes since v1: - Fix incorrect use of "it's" Changes since v2: - Add reproduction recipe Signed-off-by:Lyude <cpaul@redhat.com> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Fixes: 62e0fb88 ("drm/i915/skl: Update plane watermarks atomically during plane updates") Signed-off-by:
Lyude <cpaul@redhat.com> Testcase: kms_plane Signed-off-by:
Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/1472488288-27280-1-git-send-email-cpaul@redhat.com Cc: drm-intel-fixes@lists.freedesktop.org Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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