[PATCH v2 02/21] drm: Evaluate struct drm_device.vblank_disable_immediate on each use

[Thomas Zimmermann]

VBLANK interrupts can be disabled immediately or with a delay, where the
latter is the default. The former option can be selected by setting
get_vblank_timestamp, and enabling vblank_disable_immediate in struct
drm_device.

The setup is only evaluated once when DRM initializes VBLANKs. Evaluating
the settings on each use of vblank_disable_immediate will allow for easy
integration of CRTC VBLANK functions.

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
---
 drivers/gpu/drm/drm_vblank.c | 31 ++++++++++++++-----------------
 1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 3f1dd54cc8bb..abb085c67d82 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -481,19 +481,6 @@ int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs)
 
 	DRM_INFO("Supports vblank timestamp caching Rev 2 (21.10.2013).\n");
 
-	/* Driver specific high-precision vblank timestamping supported? */
-	if (dev->driver->get_vblank_timestamp)
-		DRM_INFO("Driver supports precise vblank timestamp query.\n");
-	else
-		DRM_INFO("No driver support for vblank timestamp query.\n");
-
-	/* Must have precise timestamping for reliable vblank instant disable */
-	if (dev->vblank_disable_immediate && !dev->driver->get_vblank_timestamp) {
-		dev->vblank_disable_immediate = false;
-		DRM_INFO("Setting vblank_disable_immediate to false because "
-			 "get_vblank_timestamp == NULL\n");
-	}
-
 	return 0;
 
 err:
@@ -1070,6 +1057,15 @@ int drm_crtc_vblank_get(struct drm_crtc *crtc)
 }
 EXPORT_SYMBOL(drm_crtc_vblank_get);
 
+static bool __vblank_disable_immediate(struct drm_device *dev, unsigned int pipe)
+{
+	if (!dev->vblank_disable_immediate)
+		return false;
+	if (!dev->driver->get_vblank_timestamp)
+		return false;
+	return true;
+}
+
 static void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
 {
 	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
@@ -1086,7 +1082,7 @@ static void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
 			return;
 		else if (drm_vblank_offdelay < 0)
 			vblank_disable_fn(&vblank->disable_timer);
-		else if (!dev->vblank_disable_immediate)
+		else if (__vblank_disable_immediate(dev, pipe))
 			mod_timer(&vblank->disable_timer,
 				  jiffies + ((drm_vblank_offdelay * HZ)/1000));
 	}
@@ -1663,7 +1659,7 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
 	/* If the counter is currently enabled and accurate, short-circuit
 	 * queries to return the cached timestamp of the last vblank.
 	 */
-	if (dev->vblank_disable_immediate &&
+	if (__vblank_disable_immediate(dev, pipe) &&
 	    drm_wait_vblank_is_query(vblwait) &&
 	    READ_ONCE(vblank->enabled)) {
 		drm_wait_vblank_reply(dev, pipe, &vblwait->reply);
@@ -1820,7 +1816,7 @@ bool drm_handle_vblank(struct drm_device *dev, unsigned int pipe)
 	 * been signaled. The disable has to be last (after
 	 * drm_handle_vblank_events) so that the timestamp is always accurate.
 	 */
-	disable_irq = (dev->vblank_disable_immediate &&
+	disable_irq = (__vblank_disable_immediate(dev, pipe) &&
 		       drm_vblank_offdelay > 0 &&
 		       !atomic_read(&vblank->refcount));
 
@@ -1893,7 +1889,8 @@ int drm_crtc_get_sequence_ioctl(struct drm_device *dev, void *data,
 	pipe = drm_crtc_index(crtc);
 
 	vblank = &dev->vblank[pipe];
-	vblank_enabled = dev->vblank_disable_immediate && READ_ONCE(vblank->enabled);
+	vblank_enabled = __vblank_disable_immediate(dev, pipe) &&
+			 READ_ONCE(vblank->enabled);
 
 	if (!vblank_enabled) {
 		ret = drm_crtc_vblank_get(crtc);
-- 
2.24.1