[PATCH v2 11/19] drm: Add dev->vblank_disable_immediate flag

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

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 at intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 Documentation/DocBook/drm.tmpl |  6 ++++++
 drivers/gpu/drm/drm_irq.c      |  2 +-
 include/drm/drmP.h             | 10 ++++++++++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 1cbe2a0..3ec4b2b 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
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 99145c4..8dbcc3f 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -994,7 +994,7 @@ void drm_vblank_put(struct drm_device *dev, int crtc)
 
 	/* Last user schedules interrupt disable */
 	if (atomic_dec_and_test(&vblank->refcount)) {
-		if (drm_vblank_offdelay < 0)
+		if (dev->vblank_disable_immediate || drm_vblank_offdelay < 0)
 			vblank_disable_fn((unsigned long)vblank);
 		else if (drm_vblank_offdelay > 0)
 			mod_timer(&vblank->disable_timer,
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index cdcc60b..3c22c35 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1077,6 +1077,16 @@ struct drm_device {
 	 */
 	bool vblank_disable_allowed;
 
+	/*
+	 * If true, vblank interrupt will be disabled immediately when the
+	 * refcount drops to zero, as opposed to via the vblank disable
+	 * timer.
+	 * This can be set to true it the hardware has a working vblank
+	 * counter and the driver uses drm_vblank_on() and drm_vblank_off()
+	 * appropriately.
+	 */
+	bool vblank_disable_immediate;
+
 	/* array of size num_crtcs */
 	struct drm_vblank_crtc *vblank;
 
-- 
1.8.5.5