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authorVille Syrjälä <ville.syrjala@linux.intel.com>2014-08-06 14:49:49 +0300
committerDaniel Vetter <daniel.vetter@ffwll.ch>2014-08-06 22:39:25 +0200
commitf8ad028cc033f75fc479ca1c30e2ea4ba56e5269 (patch)
tree57a183cb4277f706bccdcd0e48d22a72537913fa /drivers/gpu/drm/drm_panel.c
parent812e7465a7decf3cca0b5f71977a25eecd9626a4 (diff)
drm: Avoid random vblank counter jumps if the hardware counter has been reset
When drm_vblank_on() is called the hardware vblank counter may have been reset, so we can't trust that the old values sampled prior to drm_vblank_off() have anything to do with the new values. So update the .last count in drm_vblank_on() to make the first drm_vblank_enable() consider that as the reference point. This will correct the user space visible counter to account for the time between drm_vblank_on() and the first drm_vblank_enable() calls. For extra safety subtract one from the .last count in drm_vblank_on() to make sure that user space will never see the same counter value before and after modeset. Reviewed-by: Matt Roper <matthew.d.roper@intel.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'drivers/gpu/drm/drm_panel.c')
0 files changed, 0 insertions, 0 deletions