diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index edb3bb83e1a9..61bef9609b24 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -1768,10 +1768,6 @@ int amdgpu_device_resume(struct drm_device *dev, bool resume, bool fbcon);
 u32 amdgpu_get_vblank_counter_kms(struct drm_device *dev, unsigned int pipe);
 int amdgpu_enable_vblank_kms(struct drm_device *dev, unsigned int pipe);
 void amdgpu_disable_vblank_kms(struct drm_device *dev, unsigned int pipe);
-bool amdgpu_get_vblank_timestamp_kms(struct drm_device *dev, unsigned int pipe,
-				     int *max_error,
-				     struct timeval *vblank_time,
-				     bool in_vblank_irq);
 long amdgpu_kms_compat_ioctl(struct file *filp, unsigned int cmd,
 			     unsigned long arg);
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index 8a61296fd4cc..ba169a0699d5 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -692,7 +692,7 @@ static struct drm_driver kms_driver = {
 	.get_vblank_counter = amdgpu_get_vblank_counter_kms,
 	.enable_vblank = amdgpu_enable_vblank_kms,
 	.disable_vblank = amdgpu_disable_vblank_kms,
-	.get_vblank_timestamp = amdgpu_get_vblank_timestamp_kms,
+	.get_vblank_timestamp = drm_calc_vbltimestamp_from_scanoutpos,
 	.get_scanout_position = amdgpu_get_crtc_scanoutpos,
 #if defined(CONFIG_DEBUG_FS)
 	.debugfs_init = amdgpu_debugfs_init,
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
index ad295e822d45..32a492bd4e51 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
@@ -827,47 +827,6 @@ void amdgpu_disable_vblank_kms(struct drm_device *dev, unsigned int pipe)
 	amdgpu_irq_put(adev, &adev->crtc_irq, idx);
 }
 
-/**
- * amdgpu_get_vblank_timestamp_kms - get vblank timestamp
- *
- * @dev: drm dev pointer
- * @crtc: crtc to get the timestamp for
- * @max_error: max error
- * @vblank_time: time value
- * @in_vblank_irq: called from drm_handle_vblank()
- *
- * Gets the timestamp on the requested crtc based on the
- * scanout position.  (all asics).
- * Returns true on success, false on failure.
- */
-bool amdgpu_get_vblank_timestamp_kms(struct drm_device *dev, unsigned int pipe,
-				     int *max_error,
-				     struct timeval *vblank_time,
-				     bool in_vblank_irq)
-{
-	struct drm_crtc *crtc;
-	struct amdgpu_device *adev = dev->dev_private;
-
-	if (pipe >= dev->num_crtcs) {
-		DRM_ERROR("Invalid crtc %u\n", pipe);
-		return false;
-	}
-
-	/* Get associated drm_crtc: */
-	crtc = &adev->mode_info.crtcs[pipe]->base;
-	if (!crtc) {
-		/* This can occur on driver load if some component fails to
-		 * initialize completely and driver is unloaded */
-		DRM_ERROR("Uninitialized crtc %d\n", pipe);
-		return false;
-	}
-
-	/* Helper routine in DRM core does all the work: */
-	return drm_calc_vbltimestamp_from_scanoutpos(dev, pipe, max_error,
-						     vblank_time, in_vblank_irq,
-						     &crtc->hwmode);
-}
-
 const struct drm_ioctl_desc amdgpu_ioctls_kms[] = {
 	DRM_IOCTL_DEF_DRV(AMDGPU_GEM_CREATE, amdgpu_gem_create_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
 	DRM_IOCTL_DEF_DRV(AMDGPU_CTX, amdgpu_ctx_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 059c3346db68..61d726b1f810 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -659,6 +659,8 @@ void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 	if (WARN_ON(pipe >= dev->num_crtcs))
 		return;
 
+	WARN_ON(drm_drv_uses_atomic_modeset(dev) && vblank->enabled);
+
 	/* Valid dotclock? */
 	if (dotclock > 0) {
 		int frame_size = mode->crtc_htotal * mode->crtc_vtotal;
@@ -682,6 +684,7 @@ void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 
 	vblank->linedur_ns  = linedur_ns;
 	vblank->framedur_ns = framedur_ns;
+	vblank->hwmode = *mode;
 
 	DRM_DEBUG("crtc %u: hwmode: htotal %d, vtotal %d, vdisplay %d\n",
 		  crtc->base.id, mode->crtc_htotal,
@@ -702,7 +705,6 @@ EXPORT_SYMBOL(drm_calc_timestamping_constants);
  *     True when called from drm_crtc_handle_vblank().  Some drivers
  *     need to apply some workarounds for gpu-specific vblank irq quirks
  *     if flag is set.
- * @mode: mode which defines the scanout timings
  *
  * Implements calculation of exact vblank timestamps from given drm_display_mode
  * timings and current video scanout position of a CRTC. This can be called from
@@ -722,6 +724,13 @@ EXPORT_SYMBOL(drm_calc_timestamping_constants);
  * returns as no operation if a doublescan or interlaced video mode is
  * active. Higher level code is expected to handle this.
  *
+ * This function can be used to implement the &drm_driver.get_vblank_timestamp
+ * directly, if the driver implements the &drm_driver.get_scanout_position hook.
+ *
+ * Note that atomic drivers must call drm_calc_timestamping_constants() before
+ * enabling a CRTC. The atomic helpers already take care of that in
+ * drm_atomic_helper_update_legacy_modeset_state().
+ *
  * Returns:
  *
  * Returns true on success, and false on failure, i.e. when no accurate
@@ -731,17 +740,24 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
 					   unsigned int pipe,
 					   int *max_error,
 					   struct timeval *vblank_time,
-					   bool in_vblank_irq,
-					   const struct drm_display_mode *mode)
+					   bool in_vblank_irq)
 {
 	struct timeval tv_etime;
 	ktime_t stime, etime;
 	unsigned int vbl_status;
+	struct drm_crtc *crtc;
+	const struct drm_display_mode *mode;
+	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
 	int vpos, hpos, i;
 	int delta_ns, duration_ns;
 	unsigned flags = in_vblank_irq ? DRM_CALLED_FROM_VBLIRQ : 0;
 
-	if (pipe >= dev->num_crtcs) {
+	if (!drm_core_check_feature(dev, DRIVER_MODESET))
+		return false;
+
+	crtc = drm_crtc_from_index(dev, pipe);
+
+	if (pipe >= dev->num_crtcs || !crtc) {
 		DRM_ERROR("Invalid crtc %u\n", pipe);
 		return false;
 	}
@@ -752,6 +768,11 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
 		return false;
 	}
 
+	if (drm_drv_uses_atomic_modeset(dev))
+		mode = &vblank->hwmode;
+	else
+		mode = &crtc->hwmode;
+
 	/* If mode timing undefined, just return as no-op:
 	 * Happens during initial modesetting of a crtc.
 	 */
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 6c8a7e1284c3..feadfea77354 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -964,37 +964,6 @@ int intel_get_crtc_scanline(struct intel_crtc *crtc)
 	return position;
 }
 
-static bool i915_get_vblank_timestamp(struct drm_device *dev, unsigned int pipe,
-			      int *max_error,
-			      struct timeval *vblank_time,
-			      bool in_vblank_irq)
-{
-	struct drm_i915_private *dev_priv = to_i915(dev);
-	struct intel_crtc *crtc;
-
-	if (pipe >= INTEL_INFO(dev_priv)->num_pipes) {
-		DRM_ERROR("Invalid crtc %u\n", pipe);
-		return false;
-	}
-
-	/* Get drm_crtc to timestamp: */
-	crtc = intel_get_crtc_for_pipe(dev_priv, pipe);
-	if (crtc == NULL) {
-		DRM_ERROR("Invalid crtc %u\n", pipe);
-		return false;
-	}
-
-	if (!crtc->base.hwmode.crtc_clock) {
-		DRM_DEBUG_KMS("crtc %u is disabled\n", pipe);
-		return false;
-	}
-
-	/* Helper routine in DRM core does all the work: */
-	return drm_calc_vbltimestamp_from_scanoutpos(dev, pipe, max_error,
-						     vblank_time, in_vblank_irq,
-						     &crtc->base.hwmode);
-}
-
 static void ironlake_rps_change_irq_handler(struct drm_i915_private *dev_priv)
 {
 	u32 busy_up, busy_down, max_avg, min_avg;
@@ -4328,7 +4297,7 @@ void intel_irq_init(struct drm_i915_private *dev_priv)
 
 	dev_priv->hotplug.hpd_storm_threshold = HPD_STORM_DEFAULT_THRESHOLD;
 
-	dev->driver->get_vblank_timestamp = i915_get_vblank_timestamp;
+	dev->driver->get_vblank_timestamp = drm_calc_vbltimestamp_from_scanoutpos;
 	dev->driver->get_scanout_position = i915_get_crtc_scanoutpos;
 
 	if (IS_CHERRYVIEW(dev_priv)) {
diff --git a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c
index 16184ccbdd3b..6ba216b8bba9 100644
--- a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c
+++ b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c
@@ -595,30 +595,6 @@ static int mdp5_get_scanoutpos(struct drm_device *dev, unsigned int pipe,
 	return ret;
 }
 
-static bool mdp5_get_vblank_timestamp(struct drm_device *dev, unsigned int pipe,
-				      int *max_error,
-				      struct timeval *vblank_time,
-				      bool in_vblank_irq)
-{
-	struct msm_drm_private *priv = dev->dev_private;
-	struct drm_crtc *crtc;
-
-	if (pipe < 0 || pipe >= priv->num_crtcs) {
-		DRM_ERROR("Invalid crtc %d\n", pipe);
-		return false;
-	}
-
-	crtc = priv->crtcs[pipe];
-	if (!crtc) {
-		DRM_ERROR("Invalid crtc %d\n", pipe);
-		return false;
-	}
-
-	return drm_calc_vbltimestamp_from_scanoutpos(dev, pipe, max_error,
-						     vblank_time, in_vblank_irq,
-						     &crtc->mode);
-}
-
 static u32 mdp5_get_vblank_counter(struct drm_device *dev, unsigned int pipe)
 {
 	struct msm_drm_private *priv = dev->dev_private;
@@ -728,7 +704,7 @@ struct msm_kms *mdp5_kms_init(struct drm_device *dev)
 	dev->mode_config.max_width = 0xffff;
 	dev->mode_config.max_height = 0xffff;
 
-	dev->driver->get_vblank_timestamp = mdp5_get_vblank_timestamp;
+	dev->driver->get_vblank_timestamp = drm_calc_vbltimestamp_from_scanoutpos;
 	dev->driver->get_scanout_position = mdp5_get_scanoutpos;
 	dev->driver->get_vblank_counter = mdp5_get_vblank_counter;
 	dev->max_vblank_count = 0xffffffff;
diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c
index be8ec18ba126..e4bdac13d4e9 100644
--- a/drivers/gpu/drm/nouveau/nouveau_display.c
+++ b/drivers/gpu/drm/nouveau/nouveau_display.c
@@ -156,28 +156,6 @@ nouveau_display_scanoutpos(struct drm_device *dev, unsigned int pipe,
 	return 0;
 }
 
-bool
-nouveau_display_vblstamp(struct drm_device *dev, unsigned int pipe,
-			 int *max_error, struct timeval *time, bool in_vblank_irq)
-{
-	struct drm_crtc *crtc;
-
-	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
-		if (nouveau_crtc(crtc)->index == pipe) {
-			struct drm_display_mode *mode;
-			if (drm_drv_uses_atomic_modeset(dev))
-				mode = &crtc->state->adjusted_mode;
-			else
-				mode = &crtc->hwmode;
-			return drm_calc_vbltimestamp_from_scanoutpos(dev,
-					pipe, max_error, time, in_vblank_irq,
-					mode);
-		}
-	}
-
-	return false;
-}
-
 static void
 nouveau_display_vblank_fini(struct drm_device *dev)
 {
diff --git a/drivers/gpu/drm/nouveau/nouveau_display.h b/drivers/gpu/drm/nouveau/nouveau_display.h
index f821fc9e2de3..8360a85ed5ef 100644
--- a/drivers/gpu/drm/nouveau/nouveau_display.h
+++ b/drivers/gpu/drm/nouveau/nouveau_display.h
@@ -71,8 +71,6 @@ void nouveau_display_vblank_disable(struct drm_device *, unsigned int);
 int  nouveau_display_scanoutpos(struct drm_device *, unsigned int,
 				unsigned int, int *, int *, ktime_t *,
 				ktime_t *, const struct drm_display_mode *);
-bool  nouveau_display_vblstamp(struct drm_device *, unsigned int, int *,
-			       struct timeval *, bool);
 
 int  nouveau_crtc_page_flip(struct drm_crtc *crtc, struct drm_framebuffer *fb,
 			    struct drm_pending_vblank_event *event,
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index ec719df619a6..1f751a3f570c 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -978,7 +978,7 @@ driver_stub = {
 	.enable_vblank = nouveau_display_vblank_enable,
 	.disable_vblank = nouveau_display_vblank_disable,
 	.get_scanout_position = nouveau_display_scanoutpos,
-	.get_vblank_timestamp = nouveau_display_vblstamp,
+	.get_vblank_timestamp = drm_calc_vbltimestamp_from_scanoutpos,
 
 	.ioctls = nouveau_ioctls,
 	.num_ioctls = ARRAY_SIZE(nouveau_ioctls),
diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
index 5fbbc6ac165d..a4bf09cd33f7 100644
--- a/drivers/gpu/drm/radeon/radeon_drv.c
+++ b/drivers/gpu/drm/radeon/radeon_drv.c
@@ -114,10 +114,6 @@ int radeon_resume_kms(struct drm_device *dev, bool resume, bool fbcon);
 u32 radeon_get_vblank_counter_kms(struct drm_device *dev, unsigned int pipe);
 int radeon_enable_vblank_kms(struct drm_device *dev, unsigned int pipe);
 void radeon_disable_vblank_kms(struct drm_device *dev, unsigned int pipe);
-bool radeon_get_vblank_timestamp_kms(struct drm_device *dev, unsigned int pipe,
-				     int *max_error,
-				     struct timeval *vblank_time,
-				     bool in_vblank_irq);
 void radeon_driver_irq_preinstall_kms(struct drm_device *dev);
 int radeon_driver_irq_postinstall_kms(struct drm_device *dev);
 void radeon_driver_irq_uninstall_kms(struct drm_device *dev);
@@ -543,7 +539,7 @@ static struct drm_driver kms_driver = {
 	.get_vblank_counter = radeon_get_vblank_counter_kms,
 	.enable_vblank = radeon_enable_vblank_kms,
 	.disable_vblank = radeon_disable_vblank_kms,
-	.get_vblank_timestamp = radeon_get_vblank_timestamp_kms,
+	.get_vblank_timestamp = drm_calc_vbltimestamp_from_scanoutpos,
 	.get_scanout_position = radeon_get_crtc_scanoutpos,
 	.irq_preinstall = radeon_driver_irq_preinstall_kms,
 	.irq_postinstall = radeon_driver_irq_postinstall_kms,
diff --git a/drivers/gpu/drm/radeon/radeon_kms.c b/drivers/gpu/drm/radeon/radeon_kms.c
index 41765d18f863..33b8b3d22969 100644
--- a/drivers/gpu/drm/radeon/radeon_kms.c
+++ b/drivers/gpu/drm/radeon/radeon_kms.c
@@ -857,43 +857,6 @@ void radeon_disable_vblank_kms(struct drm_device *dev, int crtc)
 	spin_unlock_irqrestore(&rdev->irq.lock, irqflags);
 }
 
-/**
- * radeon_get_vblank_timestamp_kms - get vblank timestamp
- *
- * @dev: drm dev pointer
- * @crtc: crtc to get the timestamp for
- * @max_error: max error
- * @vblank_time: time value
- * @flags: flags passed to the driver
- *
- * Gets the timestamp on the requested crtc based on the
- * scanout position.  (all asics).
- * Returns true on success, false on failure.
- */
-bool radeon_get_vblank_timestamp_kms(struct drm_device *dev, int crtc,
-				     int *max_error,
-				     struct timeval *vblank_time,
-				     bool in_vblank_irq)
-{
-	struct drm_crtc *drmcrtc;
-	struct radeon_device *rdev = dev->dev_private;
-
-	if (crtc < 0 || crtc >= dev->num_crtcs) {
-		DRM_ERROR("Invalid crtc %d\n", crtc);
-		return false;
-	}
-
-	/* Get associated drm_crtc: */
-	drmcrtc = &rdev->mode_info.crtcs[crtc]->base;
-	if (!drmcrtc)
-		return false;
-
-	/* Helper routine in DRM core does all the work: */
-	return drm_calc_vbltimestamp_from_scanoutpos(dev, crtc, max_error,
-						     vblank_time, in_vblank_irq,
-						     &drmcrtc->hwmode);
-}
-
 const struct drm_ioctl_desc radeon_ioctls_kms[] = {
 	DRM_IOCTL_DEF_DRV(RADEON_CP_INIT, drm_invalid_op, DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY),
 	DRM_IOCTL_DEF_DRV(RADEON_CP_START, drm_invalid_op, DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY),
diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index 18bd0d816fe3..2567d6c9a4ee 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -270,19 +270,6 @@ int vc4_crtc_get_scanoutpos(struct drm_device *dev, unsigned int crtc_id,
 	return ret;
 }
 
-bool vc4_crtc_get_vblank_timestamp(struct drm_device *dev, unsigned int crtc_id,
-				  int *max_error, struct timeval *vblank_time,
-				  bool in_vblank_irq)
-{
-	struct drm_crtc *crtc = drm_crtc_from_index(dev, crtc_id);
-	struct drm_crtc_state *state = crtc->state;
-
-	/* Helper routine in DRM core does all the work: */
-	return drm_calc_vbltimestamp_from_scanoutpos(dev, crtc_id, max_error,
-						     vblank_time, in_vblank_irq,
-						     &state->adjusted_mode);
-}
-
 static void vc4_crtc_destroy(struct drm_crtc *crtc)
 {
 	drm_crtc_cleanup(crtc);
diff --git a/drivers/gpu/drm/vc4/vc4_drv.c b/drivers/gpu/drm/vc4/vc4_drv.c
index 61e674baf3a6..e864256e12e5 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.c
+++ b/drivers/gpu/drm/vc4/vc4_drv.c
@@ -154,7 +154,7 @@ static struct drm_driver vc4_drm_driver = {
 	.irq_uninstall = vc4_irq_uninstall,
 
 	.get_scanout_position = vc4_crtc_get_scanoutpos,
-	.get_vblank_timestamp = vc4_crtc_get_vblank_timestamp,
+	.get_vblank_timestamp = drm_calc_vbltimestamp_from_scanoutpos,
 
 #if defined(CONFIG_DEBUG_FS)
 	.debugfs_init = vc4_debugfs_init,
diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index 815cdeb54971..64c92e0eb8f7 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -450,9 +450,6 @@ int vc4_crtc_get_scanoutpos(struct drm_device *dev, unsigned int crtc_id,
 			    unsigned int flags, int *vpos, int *hpos,
 			    ktime_t *stime, ktime_t *etime,
 			    const struct drm_display_mode *mode);
-bool vc4_crtc_get_vblank_timestamp(struct drm_device *dev, unsigned int crtc_id,
-				  int *max_error, struct timeval *vblank_time,
-				  bool in_vblank_irq);
 
 /* vc4_debugfs.c */
 int vc4_debugfs_init(struct drm_minor *minor);
diff --git a/include/drm/drm_irq.h b/include/drm/drm_irq.h
index 445406efb8dc..b489cc856e7a 100644
--- a/include/drm/drm_irq.h
+++ b/include/drm/drm_irq.h
@@ -121,6 +121,18 @@ struct drm_vblank_crtc {
 	 * drm_calc_timestamping_constants().
 	 */
 	int linedur_ns;
+
+	/**
+	 * @hwmode:
+	 *
+	 * Cache of the current hardware display mode. Only valide when @enabled
+	 * is set. This is used by helpers like
+	 * drm_calc_vbltimestamp_from_scanoutpos(). We can't just access the
+	 * hardware mode by e.g. looking at &drm_crtc_state.adjusted_mode,
+	 * because that one is really hard to get at from interrupt context.
+	 */
+	struct drm_display_mode hwmode;
+
 	/**
 	 * @enabled: Tracks the enabling state of the corresponding &drm_crtc to
 	 * avoid double-disabling and hence corrupting saved state. Needed by
@@ -156,8 +168,7 @@ u32 drm_accurate_vblank_count(struct drm_crtc *crtc);
 bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
 					   unsigned int pipe, int *max_error,
 					   struct timeval *vblank_time,
-					   bool in_vblank_irq,
-					   const struct drm_display_mode *mode);
+					   bool in_vblank_irq);
 void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 				     const struct drm_display_mode *mode);
 
