Commits
Ville Syrjälä committed 7ffd7a68511
drm: Always reject drm_vblank_get() after drm_vblank_off()
Make sure drm_vblank_get() never succeeds when called between
drm_vblank_off() and drm_vblank_on(). Borrow a trick from the
old drm_vblank_{pre,post}_modeset() functions and just bump
the refcount in drm_vblank_off() and drop it in drm_vblank_on().
When drm_vblank_get() encounters a >0 refcount and the vblank
interrupt is already disabled it will simply return -EINVAL.
Hopefully the use of inmodeset won't conflict badly with
drm_vblank_{pre,post}_modeset().
For i915 there's a window between drm_vblank_off() and marking the
crtc as inactive where the current code still allows drm_vblank_get().
v2: Describe what drm_vblank_get() does to explain how
a simple refcount bump manages to fix things (Daniel)
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>