diff --git a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c
index 88fe256c1931..4e8ed739f558 100644
--- a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c
+++ b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c
@@ -374,6 +374,7 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
 	struct drm_device *dev = crtc->dev;
 	struct plane_state pstates[STAGE_MAX + 1];
 	const struct mdp5_cfg_hw *hw_cfg;
+	const struct drm_plane_state *pstate;
 	int cnt = 0, i;
 
 	DBG("%s: check", mdp5_crtc->name);
@@ -382,20 +383,13 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
 	 * and that we don't have conflicting mixer stages:
 	 */
 	hw_cfg = mdp5_cfg_get_hw_config(mdp5_kms->cfg);
-	drm_atomic_crtc_state_for_each_plane(plane, state) {
-		struct drm_plane_state *pstate;
+	drm_atomic_crtc_state_for_each_plane_state(plane, pstate, state) {
 		if (cnt >= (hw_cfg->lm.nb_stages)) {
 			dev_err(dev->dev, "too many planes!\n");
 			return -EINVAL;
 		}
 
-		pstate = state->state->plane_states[drm_plane_index(plane)];
 
-		/* plane might not have changed, in which case take
-		 * current state:
-		 */
-		if (!pstate)
-			pstate = plane->state;
 		pstates[cnt].plane = plane;
 		pstates[cnt].state = to_mdp5_plane_state(pstate);
 
diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index 904d0754ad78..ba2e373ec901 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -395,6 +395,7 @@ static int vc4_crtc_atomic_check(struct drm_crtc *crtc,
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct drm_plane *plane;
 	unsigned long flags;
+	const struct drm_plane_state *plane_state;
 	u32 dlist_count = 0;
 	int ret;
 
@@ -404,18 +405,8 @@ static int vc4_crtc_atomic_check(struct drm_crtc *crtc,
 	if (hweight32(state->connector_mask) > 1)
 		return -EINVAL;
 
-	drm_atomic_crtc_state_for_each_plane(plane, state) {
-		struct drm_plane_state *plane_state =
-			state->state->plane_states[drm_plane_index(plane)];
-
-		/* plane might not have changed, in which case take
-		 * current state:
-		 */
-		if (!plane_state)
-			plane_state = plane->state;
-
+	drm_atomic_crtc_state_for_each_plane_state(plane, plane_state, state)
 		dlist_count += vc4_plane_dlist_size(plane_state);
-	}
 
 	dlist_count++; /* Account for SCALER_CTL0_END. */
 
diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index 37cac59401d7..c799baabc008 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -469,7 +469,7 @@ int vc4_kms_load(struct drm_device *dev);
 struct drm_plane *vc4_plane_init(struct drm_device *dev,
 				 enum drm_plane_type type);
 u32 vc4_plane_write_dlist(struct drm_plane *plane, u32 __iomem *dlist);
-u32 vc4_plane_dlist_size(struct drm_plane_state *state);
+u32 vc4_plane_dlist_size(const struct drm_plane_state *state);
 void vc4_plane_async_set_fb(struct drm_plane *plane,
 			    struct drm_framebuffer *fb);
 
diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index 4037b52fde31..5d2c3d9fd17a 100644
--- a/drivers/gpu/drm/vc4/vc4_plane.c
+++ b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -690,9 +690,10 @@ u32 vc4_plane_write_dlist(struct drm_plane *plane, u32 __iomem *dlist)
 	return vc4_state->dlist_count;
 }
 
-u32 vc4_plane_dlist_size(struct drm_plane_state *state)
+u32 vc4_plane_dlist_size(const struct drm_plane_state *state)
 {
-	struct vc4_plane_state *vc4_state = to_vc4_plane_state(state);
+	const struct vc4_plane_state *vc4_state =
+		container_of(state, typeof(*vc4_state), base);
 
 	return vc4_state->dlist_count;
 }
diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
index 92c84e9ab09a..4e97186293be 100644
--- a/include/drm/drm_atomic.h
+++ b/include/drm/drm_atomic.h
@@ -109,6 +109,42 @@ drm_atomic_get_existing_connector_state(struct drm_atomic_state *state,
 	return state->connector_states[index];
 }
 
+/**
+ * __drm_atomic_get_current_plane_state - get current plane state
+ * @state: global atomic state object
+ * @plane: plane to grab
+ *
+ * This function returns the plane state for the given plane, either from
+ * @state, or if the plane isn't part of the atomic state update, from @plane.
+ * This is useful in atomic check callbacks, when drivers need to peek at, but
+ * not change, state of other planes, since it avoids threading an error code
+ * back up the call chain.
+ *
+ * WARNING:
+ *
+ * Note that this function is in general unsafe since it doesn't check for the
+ * required locking for access state structures. Drivers must ensure that it is
+ * save to access the returned state structure through other means. One commone
+ * example is when planes are fixed to a single CRTC, and the driver knows that
+ * the CRTC locks is held already. In that case holding the CRTC locks gives a
+ * read-lock on all planes connected to that CRTC. But if planes can be
+ * reassigned things get more tricky. In that case it's better to use
+ * drm_atomic_get_plane_state and wire up full error handling.
+ *
+ * Returns:
+ *
+ * Read-only pointer to the current plane state.
+ */
+static inline const struct drm_plane_state *
+__drm_atomic_get_current_plane_state(struct drm_atomic_state *state,
+				     struct drm_plane *plane)
+{
+	if (state->plane_states[drm_plane_index(plane)])
+		return state->plane_states[drm_plane_index(plane)];
+
+	return plane->state;
+}
+
 int __must_check
 drm_atomic_set_mode_for_crtc(struct drm_crtc_state *state,
 			     struct drm_display_mode *mode);
diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
index d473dcc91f54..b03bd83703b4 100644
--- a/include/drm/drm_atomic_helper.h
+++ b/include/drm/drm_atomic_helper.h
@@ -159,7 +159,7 @@ void drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
  * This iterates over the current state, useful (for example) when applying
  * atomic state after it has been checked and swapped.  To iterate over the
  * planes which *will* be attached (for ->atomic_check()) see
- * drm_crtc_for_each_pending_plane()
+ * drm_crtc_for_each_pending_plane().
  */
 #define drm_atomic_crtc_for_each_plane(plane, crtc) \
 	drm_for_each_plane_mask(plane, (crtc)->dev, (crtc)->state->plane_mask)
@@ -171,11 +171,31 @@ void drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
  *
  * Similar to drm_crtc_for_each_plane(), but iterates the planes that will be
  * attached if the specified state is applied.  Useful during (for example)
- * ->atomic_check() operations, to validate the incoming state
+ * ->atomic_check() operations, to validate the incoming state.
  */
 #define drm_atomic_crtc_state_for_each_plane(plane, crtc_state) \
 	drm_for_each_plane_mask(plane, (crtc_state)->state->dev, (crtc_state)->plane_mask)
 
+/**
+ * drm_crtc_atomic_state_for_each_plane_state - iterate over attached planes in new state
+ * @plane: the loop cursor
+ * @plane_state: loop cursor for the plane's state, must be const
+ * @crtc_state: the incoming crtc-state
+ *
+ * Similar to drm_crtc_for_each_plane(), but iterates the planes that will be
+ * attached if the specified state is applied.  Useful during (for example)
+ * ->atomic_check() operations, to validate the incoming state.
+ *
+ * Compared to just drm_atomic_crtc_state_for_each_plane() this also fills in a
+ * const plane_state. This is useful when a driver just wants to peek at other
+ * active planes on this crtc, but does not need to change it.
+ */
+#define drm_atomic_crtc_state_for_each_plane_state(plane, plane_state, crtc_state) \
+	drm_for_each_plane_mask(plane, (crtc_state)->state->dev, (crtc_state)->plane_mask) \
+		for_each_if ((plane_state = \
+			      __drm_atomic_get_current_plane_state((crtc_state)->state, \
+								   plane)))
+
 /*
  * drm_atomic_plane_disabling - check whether a plane is being disabled
  * @plane: plane object