2 files changed, 13 insertions, 7 deletions

diff --git a/drivers/char/drm/drm.h b/drivers/char/drm/drm.h
index 07a699029c3e..3f28a1551621 100644
--- a/drivers/char/drm/drm.h
+++ b/drivers/char/drm/drm.h
@@ -487,12 +487,14 @@ typedef struct drm_irq_busid {
 typedef enum {
         _DRM_VBLANK_ABSOLUTE = 0x0,     /**< Wait for specific vblank sequence number */
         _DRM_VBLANK_RELATIVE = 0x1,     /**< Wait for given number of vblanks */
+        _DRM_VBLANK_NEXTONMISS = 0x10000000,    /**< If missed, wait for next vblank */
         _DRM_VBLANK_SECONDARY = 0x20000000,     /**< Secondary display controller */
         _DRM_VBLANK_SIGNAL = 0x40000000 /**< Send signal instead of blocking */
 } drm_vblank_seq_type_t;
 
 #define _DRM_VBLANK_TYPES_MASK (_DRM_VBLANK_ABSOLUTE | _DRM_VBLANK_RELATIVE)
-#define _DRM_VBLANK_FLAGS_MASK (_DRM_VBLANK_SIGNAL | _DRM_VBLANK_SECONDARY)
+#define _DRM_VBLANK_FLAGS_MASK (_DRM_VBLANK_SIGNAL | _DRM_VBLANK_SECONDARY | \
+                                _DRM_VBLANK_NEXTONMISS)
 
 struct drm_wait_vblank_request {
         drm_vblank_seq_type_t type;
diff --git a/drivers/char/drm/drm_irq.c b/drivers/char/drm/drm_irq.c
index b08608a9f026..78aae5b35c62 100644
--- a/drivers/char/drm/drm_irq.c
+++ b/drivers/char/drm/drm_irq.c
@@ -250,8 +250,7 @@ int drm_wait_vblank(DRM_IOCTL_ARGS)
         drm_wait_vblank_t vblwait;
         struct timeval now;
         int ret = 0;
-        unsigned int flags;
-        atomic_t *seq;
+        unsigned int flags, seq;
 
         if (!dev->irq)
                 return -EINVAL;
@@ -273,12 +272,12 @@ int drm_wait_vblank(DRM_IOCTL_ARGS)
                                     DRIVER_IRQ_VBL2 : DRIVER_IRQ_VBL))
                 return -EINVAL;
 
-        seq = (flags & _DRM_VBLANK_SECONDARY) ? &dev->vbl_received2 :
-              &dev->vbl_received;
+        seq = atomic_read((flags & _DRM_VBLANK_SECONDARY) ? &dev->vbl_received2
+                          : &dev->vbl_received);
 
         switch (vblwait.request.type & _DRM_VBLANK_TYPES_MASK) {
         case _DRM_VBLANK_RELATIVE:
-                vblwait.request.sequence += atomic_read(seq);
+                vblwait.request.sequence += seq;
                 vblwait.request.type &= ~_DRM_VBLANK_RELATIVE;
         case _DRM_VBLANK_ABSOLUTE:
                 break;
@@ -286,13 +285,18 @@ int drm_wait_vblank(DRM_IOCTL_ARGS)
                 return -EINVAL;
         }
 
+        if ((flags & _DRM_VBLANK_NEXTONMISS) &&
+            (seq - vblwait.request.sequence) <= (1<<23)) {
+                vblwait.request.sequence = seq + 1;
+        }
+
         if (flags & _DRM_VBLANK_SIGNAL) {
                 unsigned long irqflags;
                 drm_vbl_sig_t *vbl_sigs = (flags & _DRM_VBLANK_SECONDARY)
                                       ? &dev->vbl_sigs2 : &dev->vbl_sigs;
                 drm_vbl_sig_t *vbl_sig;
 
-                vblwait.reply.sequence = atomic_read(seq);
+                vblwait.reply.sequence = seq;
 
                 spin_lock_irqsave(&dev->vbl_lock, irqflags);