2 files changed, 61 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 913954765d9e..c781cb426bf1 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -1237,6 +1237,65 @@ void drm_crtc_vblank_on(struct drm_crtc *crtc)
 }
 EXPORT_SYMBOL(drm_crtc_vblank_on);
 
+/**
+ * drm_vblank_restore - estimated vblanks using timestamps and update it.
+ *
+ * Power manamement features can cause frame counter resets between vblank
+ * disable and enable. Drivers can then use this function in their
+ * &drm_crtc_funcs.enable_vblank implementation to estimate the vblanks since
+ * the last &drm_crtc_funcs.disable_vblank.
+ *
+ * This function is the legacy version of drm_crtc_vblank_restore().
+ */
+void drm_vblank_restore(struct drm_device *dev, unsigned int pipe)
+{
+        ktime_t t_vblank;
+        struct drm_vblank_crtc *vblank;
+        int framedur_ns;
+        u64 diff_ns;
+        u32 cur_vblank, diff = 1;
+        int count = DRM_TIMESTAMP_MAXRETRIES;
+
+        if (WARN_ON(pipe >= dev->num_crtcs))
+                return;
+
+        assert_spin_locked(&dev->vbl_lock);
+        assert_spin_locked(&dev->vblank_time_lock);
+
+        vblank = &dev->vblank[pipe];
+        WARN_ONCE((drm_debug & DRM_UT_VBL) && !vblank->framedur_ns,
+                  "Cannot compute missed vblanks without frame duration\n");
+        framedur_ns = vblank->framedur_ns;
+
+        do {
+                cur_vblank = __get_vblank_counter(dev, pipe);
+                drm_get_last_vbltimestamp(dev, pipe, &t_vblank, false);
+        } while (cur_vblank != __get_vblank_counter(dev, pipe) && --count > 0);
+
+        diff_ns = ktime_to_ns(ktime_sub(t_vblank, vblank->time));
+        if (framedur_ns)
+                diff = DIV_ROUND_CLOSEST_ULL(diff_ns, framedur_ns);
+
+
+        DRM_DEBUG_VBL("missed %d vblanks in %lld ns, frame duration=%d ns, hw_diff=%d\n",
+                      diff, diff_ns, framedur_ns, cur_vblank - vblank->last);
+        store_vblank(dev, pipe, diff, t_vblank, cur_vblank);
+}
+EXPORT_SYMBOL(drm_vblank_restore);
+
+/**
+ * drm_crtc_vblank_restore - estimate vblanks using timestamps and update it.
+ * Power manamement features can cause frame counter resets between vblank
+ * disable and enable. Drivers can then use this function in their
+ * &drm_crtc_funcs.enable_vblank implementation to estimate the vblanks since
+ * the last &drm_crtc_funcs.disable_vblank.
+ */
+void drm_crtc_vblank_restore(struct drm_crtc *crtc)
+{
+        drm_vblank_restore(crtc->dev, drm_crtc_index(crtc));
+}
+EXPORT_SYMBOL(drm_crtc_vblank_restore);
+
 static void drm_legacy_vblank_pre_modeset(struct drm_device *dev,
                                           unsigned int pipe)
 {
diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
index a4c3b0a0a197..16d46e2a6854 100644
--- a/include/drm/drm_vblank.h
+++ b/include/drm/drm_vblank.h
@@ -180,6 +180,8 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc);
 void drm_crtc_vblank_reset(struct drm_crtc *crtc);
 void drm_crtc_vblank_on(struct drm_crtc *crtc);
 u64 drm_crtc_accurate_vblank_count(struct drm_crtc *crtc);
+void drm_vblank_restore(struct drm_device *dev, unsigned int pipe);
+void drm_crtc_vblank_restore(struct drm_crtc *crtc);
 
 bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
                                            unsigned int pipe, int *max_error,