1 files changed, 22 insertions, 0 deletions

diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
index 6ad9630d4f48..e528bb2f659d 100644
--- a/include/drm/drm_vblank.h
+++ b/include/drm/drm_vblank.h
@@ -129,6 +129,26 @@ struct drm_vblank_crtc {
          */
         u32 last;
         /**
+         * @max_vblank_count:
+         *
+         * Maximum value of the vblank registers for this crtc. This value +1
+         * will result in a wrap-around of the vblank register. It is used
+         * by the vblank core to handle wrap-arounds.
+         *
+         * If set to zero the vblank core will try to guess the elapsed vblanks
+         * between times when the vblank interrupt is disabled through
+         * high-precision timestamps. That approach is suffering from small
+         * races and imprecision over longer time periods, hence exposing a
+         * hardware vblank counter is always recommended.
+         *
+         * This is the runtime configurable per-crtc maximum set through
+         * drm_crtc_set_max_vblank_count(). If this is used the driver
+         * must leave the device wide &drm_device.max_vblank_count at zero.
+         *
+         * If non-zero, &drm_crtc_funcs.get_vblank_counter must be set.
+         */
+        u32 max_vblank_count;
+        /**
          * @inmodeset: Tracks whether the vblank is disabled due to a modeset.
          * For legacy driver bit 2 additionally tracks whether an additional
          * temporary vblank reference has been acquired to paper over the
@@ -206,4 +226,6 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
 void drm_calc_timestamping_constants(struct drm_crtc *crtc,
                                      const struct drm_display_mode *mode);
 wait_queue_head_t *drm_crtc_vblank_waitqueue(struct drm_crtc *crtc);
+void drm_crtc_set_max_vblank_count(struct drm_crtc *crtc,
+                                   u32 max_vblank_count);
 #endif