drm: Add dev->vblank_disable_immediate flag

Add a flag to drm_device which will cause the vblank code to bypass the
disable timer and always disable the vblank interrupt immediately when
the last reference is dropped.

v2: Add some notes about the flag to the kernel doc

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>

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 55923d00bd52..583edbffff1a 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -3387,6 +3387,12 @@ void (*disable_vblank) (struct drm_device *dev, int crtc);</synopsis>
       module parameter or the <varname>drm_vblank_offdelay</varname> global
       variable and expressed in milliseconds. Its default value is 5000 ms.
       Zero means never disable, and a negative value means disable immediately.
+      Drivers may override the behaviour by setting the
+      <structname>drm_device</structname>
+      <structfield>vblank_disable_immediate</structfield> flag, which when set
+      causes vblank interrupts to be disabled immediately regardless of the
+      drm_vblank_offdelay value. The flag should only be set if there's a
+      properly working hardware vblank counter present.
     </para>
     <para>
       When a vertical blanking interrupt occurs drivers only need to call the