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-rw-r--r--include/drm/drm_vblank.h22
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