diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
index ba4e100e5b0f..6196410b9e98 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
@@ -192,290 +192,16 @@ static void rcar_du_output_poll_changed(struct drm_device *dev)
  * Atomic Check and Update
  */
 
-/*
- * Atomic hardware plane allocator
- *
- * The hardware plane allocator is solely based on the atomic plane states
- * without keeping any external state to avoid races between .atomic_check()
- * and .atomic_commit().
- *
- * The core idea is to avoid using a free planes bitmask that would need to be
- * shared between check and commit handlers with a collective knowledge based on
- * the allocated hardware plane(s) for each KMS plane. The allocator then loops
- * over all plane states to compute the free planes bitmask, allocates hardware
- * planes based on that bitmask, and stores the result back in the plane states.
- *
- * For this to work we need to access the current state of planes not touched by
- * the atomic update. To ensure that it won't be modified, we need to lock all
- * planes using drm_atomic_get_plane_state(). This effectively serializes atomic
- * updates from .atomic_check() up to completion (when swapping the states if
- * the check step has succeeded) or rollback (when freeing the states if the
- * check step has failed).
- *
- * Allocation is performed in the .atomic_check() handler and applied
- * automatically when the core swaps the old and new states.
- */
-
-static bool rcar_du_plane_needs_realloc(struct rcar_du_plane *plane,
-					struct rcar_du_plane_state *new_state)
-{
-	struct rcar_du_plane_state *cur_state;
-
-	cur_state = to_rcar_plane_state(plane->plane.state);
-
-	/* Lowering the number of planes doesn't strictly require reallocation
-	 * as the extra hardware plane will be freed when committing, but doing
-	 * so could lead to more fragmentation.
-	 */
-	if (!cur_state->format ||
-	    cur_state->format->planes != new_state->format->planes)
-		return true;
-
-	/* Reallocate hardware planes if the source has changed. */
-	if (cur_state->source != new_state->source)
-		return true;
-
-	return false;
-}
-
-static unsigned int rcar_du_plane_hwmask(struct rcar_du_plane_state *state)
-{
-	unsigned int mask;
-
-	if (state->hwindex == -1)
-		return 0;
-
-	mask = 1 << state->hwindex;
-	if (state->format->planes == 2)
-		mask |= 1 << ((state->hwindex + 1) % 8);
-
-	return mask;
-}
-
-/*
- * The R8A7790 DU can source frames directly from the VSP1 devices VSPD0 and
- * VSPD1. VSPD0 feeds DU0/1 plane 0, and VSPD1 feeds either DU2 plane 0 or
- * DU0/1 plane 1.
- *
- * Allocate the correct fixed plane when sourcing frames from VSPD0 or VSPD1,
- * and allocate planes in reverse index order otherwise to ensure maximum
- * availability of planes 0 and 1.
- *
- * The caller is responsible for ensuring that the requested source is
- * compatible with the DU revision.
- */
-static int rcar_du_plane_hwalloc(struct rcar_du_plane *plane,
-				 struct rcar_du_plane_state *state,
-				 unsigned int free)
-{
-	unsigned int num_planes = state->format->planes;
-	int fixed = -1;
-	int i;
-
-	if (state->source == RCAR_DU_PLANE_VSPD0) {
-		/* VSPD0 feeds plane 0 on DU0/1. */
-		if (plane->group->index != 0)
-			return -EINVAL;
-
-		fixed = 0;
-	} else if (state->source == RCAR_DU_PLANE_VSPD1) {
-		/* VSPD1 feeds plane 1 on DU0/1 or plane 0 on DU2. */
-		fixed = plane->group->index == 0 ? 1 : 0;
-	}
-
-	if (fixed >= 0)
-		return free & (1 << fixed) ? fixed : -EBUSY;
-
-	for (i = RCAR_DU_NUM_HW_PLANES - 1; i >= 0; --i) {
-		if (!(free & (1 << i)))
-			continue;
-
-		if (num_planes == 1 || free & (1 << ((i + 1) % 8)))
-			break;
-	}
-
-	return i < 0 ? -EBUSY : i;
-}
-
 static int rcar_du_atomic_check(struct drm_device *dev,
 				struct drm_atomic_state *state)
 {
-	struct rcar_du_device *rcdu = dev->dev_private;
-	unsigned int group_freed_planes[RCAR_DU_MAX_GROUPS] = { 0, };
-	unsigned int group_free_planes[RCAR_DU_MAX_GROUPS] = { 0, };
-	bool needs_realloc = false;
-	unsigned int groups = 0;
-	unsigned int i;
 	int ret;
 
 	ret = drm_atomic_helper_check(dev, state);
 	if (ret < 0)
 		return ret;
 
-	/* Check if hardware planes need to be reallocated. */
-	for (i = 0; i < dev->mode_config.num_total_plane; ++i) {
-		struct rcar_du_plane_state *plane_state;
-		struct rcar_du_plane *plane;
-		unsigned int index;
-
-		if (!state->planes[i])
-			continue;
-
-		plane = to_rcar_plane(state->planes[i]);
-		plane_state = to_rcar_plane_state(state->plane_states[i]);
-
-		dev_dbg(rcdu->dev, "%s: checking plane (%u,%u)\n", __func__,
-			plane->group->index, plane - plane->group->planes);
-
-		/* If the plane is being disabled we don't need to go through
-		 * the full reallocation procedure. Just mark the hardware
-		 * plane(s) as freed.
-		 */
-		if (!plane_state->format) {
-			dev_dbg(rcdu->dev, "%s: plane is being disabled\n",
-				__func__);
-			index = plane - plane->group->planes;
-			group_freed_planes[plane->group->index] |= 1 << index;
-			plane_state->hwindex = -1;
-			continue;
-		}
-
-		/* If the plane needs to be reallocated mark it as such, and
-		 * mark the hardware plane(s) as free.
-		 */
-		if (rcar_du_plane_needs_realloc(plane, plane_state)) {
-			dev_dbg(rcdu->dev, "%s: plane needs reallocation\n",
-				__func__);
-			groups |= 1 << plane->group->index;
-			needs_realloc = true;
-
-			index = plane - plane->group->planes;
-			group_freed_planes[plane->group->index] |= 1 << index;
-			plane_state->hwindex = -1;
-		}
-	}
-
-	if (!needs_realloc)
-		return 0;
-
-	/* Grab all plane states for the groups that need reallocation to ensure
-	 * locking and avoid racy updates. This serializes the update operation,
-	 * but there's not much we can do about it as that's the hardware
-	 * design.
-	 *
-	 * Compute the used planes mask for each group at the same time to avoid
-	 * looping over the planes separately later.
-	 */
-	while (groups) {
-		unsigned int index = ffs(groups) - 1;
-		struct rcar_du_group *group = &rcdu->groups[index];
-		unsigned int used_planes = 0;
-
-		dev_dbg(rcdu->dev, "%s: finding free planes for group %u\n",
-			__func__, index);
-
-		for (i = 0; i < group->num_planes; ++i) {
-			struct rcar_du_plane *plane = &group->planes[i];
-			struct rcar_du_plane_state *plane_state;
-			struct drm_plane_state *s;
-
-			s = drm_atomic_get_plane_state(state, &plane->plane);
-			if (IS_ERR(s))
-				return PTR_ERR(s);
-
-			/* If the plane has been freed in the above loop its
-			 * hardware planes must not be added to the used planes
-			 * bitmask. However, the current state doesn't reflect
-			 * the free state yet, as we've modified the new state
-			 * above. Use the local freed planes list to check for
-			 * that condition instead.
-			 */
-			if (group_freed_planes[index] & (1 << i)) {
-				dev_dbg(rcdu->dev,
-					"%s: plane (%u,%u) has been freed, skipping\n",
-					__func__, plane->group->index,
-					plane - plane->group->planes);
-				continue;
-			}
-
-			plane_state = to_rcar_plane_state(plane->plane.state);
-			used_planes |= rcar_du_plane_hwmask(plane_state);
-
-			dev_dbg(rcdu->dev,
-				"%s: plane (%u,%u) uses %u hwplanes (index %d)\n",
-				__func__, plane->group->index,
-				plane - plane->group->planes,
-				plane_state->format ?
-				plane_state->format->planes : 0,
-				plane_state->hwindex);
-		}
-
-		group_free_planes[index] = 0xff & ~used_planes;
-		groups &= ~(1 << index);
-
-		dev_dbg(rcdu->dev, "%s: group %u free planes mask 0x%02x\n",
-			__func__, index, group_free_planes[index]);
-	}
-
-	/* Reallocate hardware planes for each plane that needs it. */
-	for (i = 0; i < dev->mode_config.num_total_plane; ++i) {
-		struct rcar_du_plane_state *plane_state;
-		struct rcar_du_plane *plane;
-		unsigned int crtc_planes;
-		unsigned int free;
-		int idx;
-
-		if (!state->planes[i])
-			continue;
-
-		plane = to_rcar_plane(state->planes[i]);
-		plane_state = to_rcar_plane_state(state->plane_states[i]);
-
-		dev_dbg(rcdu->dev, "%s: allocating plane (%u,%u)\n", __func__,
-			plane->group->index, plane - plane->group->planes);
-
-		/* Skip planes that are being disabled or don't need to be
-		 * reallocated.
-		 */
-		if (!plane_state->format ||
-		    !rcar_du_plane_needs_realloc(plane, plane_state))
-			continue;
-
-		/* Try to allocate the plane from the free planes currently
-		 * associated with the target CRTC to avoid restarting the CRTC
-		 * group and thus minimize flicker. If it fails fall back to
-		 * allocating from all free planes.
-		 */
-		crtc_planes = to_rcar_crtc(plane_state->state.crtc)->index % 2
-			    ? plane->group->dptsr_planes
-			    : ~plane->group->dptsr_planes;
-		free = group_free_planes[plane->group->index];
-
-		idx = rcar_du_plane_hwalloc(plane, plane_state,
-					    free & crtc_planes);
-		if (idx < 0)
-			idx = rcar_du_plane_hwalloc(plane, plane_state,
-						    free);
-		if (idx < 0) {
-			dev_dbg(rcdu->dev, "%s: no available hardware plane\n",
-				__func__);
-			return idx;
-		}
-
-		dev_dbg(rcdu->dev, "%s: allocated %u hwplanes (index %u)\n",
-			__func__, plane_state->format->planes, idx);
-
-		plane_state->hwindex = idx;
-
-		group_free_planes[plane->group->index] &=
-			~rcar_du_plane_hwmask(plane_state);
-
-		dev_dbg(rcdu->dev, "%s: group %u free planes mask 0x%02x\n",
-			__func__, plane->group->index,
-			group_free_planes[plane->group->index]);
-	}
-
-	return 0;
+	return rcar_du_atomic_check_planes(dev, state);
 }
 
 struct rcar_du_commit {
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_plane.c b/drivers/gpu/drm/rcar-du/rcar_du_plane.c
index c7e0535c0e77..b868184e8385 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_plane.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_plane.c
@@ -12,6 +12,7 @@
  */
 
 #include <drm/drmP.h>
+#include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_crtc_helper.h>
@@ -25,6 +26,291 @@
 #include "rcar_du_plane.h"
 #include "rcar_du_regs.h"
 
+/* -----------------------------------------------------------------------------
+ * Atomic hardware plane allocator
+ *
+ * The hardware plane allocator is solely based on the atomic plane states
+ * without keeping any external state to avoid races between .atomic_check()
+ * and .atomic_commit().
+ *
+ * The core idea is to avoid using a free planes bitmask that would need to be
+ * shared between check and commit handlers with a collective knowledge based on
+ * the allocated hardware plane(s) for each KMS plane. The allocator then loops
+ * over all plane states to compute the free planes bitmask, allocates hardware
+ * planes based on that bitmask, and stores the result back in the plane states.
+ *
+ * For this to work we need to access the current state of planes not touched by
+ * the atomic update. To ensure that it won't be modified, we need to lock all
+ * planes using drm_atomic_get_plane_state(). This effectively serializes atomic
+ * updates from .atomic_check() up to completion (when swapping the states if
+ * the check step has succeeded) or rollback (when freeing the states if the
+ * check step has failed).
+ *
+ * Allocation is performed in the .atomic_check() handler and applied
+ * automatically when the core swaps the old and new states.
+ */
+
+static bool rcar_du_plane_needs_realloc(struct rcar_du_plane *plane,
+					struct rcar_du_plane_state *new_state)
+{
+	struct rcar_du_plane_state *cur_state;
+
+	cur_state = to_rcar_plane_state(plane->plane.state);
+
+	/* Lowering the number of planes doesn't strictly require reallocation
+	 * as the extra hardware plane will be freed when committing, but doing
+	 * so could lead to more fragmentation.
+	 */
+	if (!cur_state->format ||
+	    cur_state->format->planes != new_state->format->planes)
+		return true;
+
+	/* Reallocate hardware planes if the source has changed. */
+	if (cur_state->source != new_state->source)
+		return true;
+
+	return false;
+}
+
+static unsigned int rcar_du_plane_hwmask(struct rcar_du_plane_state *state)
+{
+	unsigned int mask;
+
+	if (state->hwindex == -1)
+		return 0;
+
+	mask = 1 << state->hwindex;
+	if (state->format->planes == 2)
+		mask |= 1 << ((state->hwindex + 1) % 8);
+
+	return mask;
+}
+
+/*
+ * The R8A7790 DU can source frames directly from the VSP1 devices VSPD0 and
+ * VSPD1. VSPD0 feeds DU0/1 plane 0, and VSPD1 feeds either DU2 plane 0 or
+ * DU0/1 plane 1.
+ *
+ * Allocate the correct fixed plane when sourcing frames from VSPD0 or VSPD1,
+ * and allocate planes in reverse index order otherwise to ensure maximum
+ * availability of planes 0 and 1.
+ *
+ * The caller is responsible for ensuring that the requested source is
+ * compatible with the DU revision.
+ */
+static int rcar_du_plane_hwalloc(struct rcar_du_plane *plane,
+				 struct rcar_du_plane_state *state,
+				 unsigned int free)
+{
+	unsigned int num_planes = state->format->planes;
+	int fixed = -1;
+	int i;
+
+	if (state->source == RCAR_DU_PLANE_VSPD0) {
+		/* VSPD0 feeds plane 0 on DU0/1. */
+		if (plane->group->index != 0)
+			return -EINVAL;
+
+		fixed = 0;
+	} else if (state->source == RCAR_DU_PLANE_VSPD1) {
+		/* VSPD1 feeds plane 1 on DU0/1 or plane 0 on DU2. */
+		fixed = plane->group->index == 0 ? 1 : 0;
+	}
+
+	if (fixed >= 0)
+		return free & (1 << fixed) ? fixed : -EBUSY;
+
+	for (i = RCAR_DU_NUM_HW_PLANES - 1; i >= 0; --i) {
+		if (!(free & (1 << i)))
+			continue;
+
+		if (num_planes == 1 || free & (1 << ((i + 1) % 8)))
+			break;
+	}
+
+	return i < 0 ? -EBUSY : i;
+}
+
+int rcar_du_atomic_check_planes(struct drm_device *dev,
+				struct drm_atomic_state *state)
+{
+	struct rcar_du_device *rcdu = dev->dev_private;
+	unsigned int group_freed_planes[RCAR_DU_MAX_GROUPS] = { 0, };
+	unsigned int group_free_planes[RCAR_DU_MAX_GROUPS] = { 0, };
+	bool needs_realloc = false;
+	unsigned int groups = 0;
+	unsigned int i;
+
+	/* Check if hardware planes need to be reallocated. */
+	for (i = 0; i < dev->mode_config.num_total_plane; ++i) {
+		struct rcar_du_plane_state *plane_state;
+		struct rcar_du_plane *plane;
+		unsigned int index;
+
+		if (!state->planes[i])
+			continue;
+
+		plane = to_rcar_plane(state->planes[i]);
+		plane_state = to_rcar_plane_state(state->plane_states[i]);
+
+		dev_dbg(rcdu->dev, "%s: checking plane (%u,%u)\n", __func__,
+			plane->group->index, plane - plane->group->planes);
+
+		/* If the plane is being disabled we don't need to go through
+		 * the full reallocation procedure. Just mark the hardware
+		 * plane(s) as freed.
+		 */
+		if (!plane_state->format) {
+			dev_dbg(rcdu->dev, "%s: plane is being disabled\n",
+				__func__);
+			index = plane - plane->group->planes;
+			group_freed_planes[plane->group->index] |= 1 << index;
+			plane_state->hwindex = -1;
+			continue;
+		}
+
+		/* If the plane needs to be reallocated mark it as such, and
+		 * mark the hardware plane(s) as free.
+		 */
+		if (rcar_du_plane_needs_realloc(plane, plane_state)) {
+			dev_dbg(rcdu->dev, "%s: plane needs reallocation\n",
+				__func__);
+			groups |= 1 << plane->group->index;
+			needs_realloc = true;
+
+			index = plane - plane->group->planes;
+			group_freed_planes[plane->group->index] |= 1 << index;
+			plane_state->hwindex = -1;
+		}
+	}
+
+	if (!needs_realloc)
+		return 0;
+
+	/* Grab all plane states for the groups that need reallocation to ensure
+	 * locking and avoid racy updates. This serializes the update operation,
+	 * but there's not much we can do about it as that's the hardware
+	 * design.
+	 *
+	 * Compute the used planes mask for each group at the same time to avoid
+	 * looping over the planes separately later.
+	 */
+	while (groups) {
+		unsigned int index = ffs(groups) - 1;
+		struct rcar_du_group *group = &rcdu->groups[index];
+		unsigned int used_planes = 0;
+
+		dev_dbg(rcdu->dev, "%s: finding free planes for group %u\n",
+			__func__, index);
+
+		for (i = 0; i < group->num_planes; ++i) {
+			struct rcar_du_plane *plane = &group->planes[i];
+			struct rcar_du_plane_state *plane_state;
+			struct drm_plane_state *s;
+
+			s = drm_atomic_get_plane_state(state, &plane->plane);
+			if (IS_ERR(s))
+				return PTR_ERR(s);
+
+			/* If the plane has been freed in the above loop its
+			 * hardware planes must not be added to the used planes
+			 * bitmask. However, the current state doesn't reflect
+			 * the free state yet, as we've modified the new state
+			 * above. Use the local freed planes list to check for
+			 * that condition instead.
+			 */
+			if (group_freed_planes[index] & (1 << i)) {
+				dev_dbg(rcdu->dev,
+					"%s: plane (%u,%u) has been freed, skipping\n",
+					__func__, plane->group->index,
+					plane - plane->group->planes);
+				continue;
+			}
+
+			plane_state = to_rcar_plane_state(plane->plane.state);
+			used_planes |= rcar_du_plane_hwmask(plane_state);
+
+			dev_dbg(rcdu->dev,
+				"%s: plane (%u,%u) uses %u hwplanes (index %d)\n",
+				__func__, plane->group->index,
+				plane - plane->group->planes,
+				plane_state->format ?
+				plane_state->format->planes : 0,
+				plane_state->hwindex);
+		}
+
+		group_free_planes[index] = 0xff & ~used_planes;
+		groups &= ~(1 << index);
+
+		dev_dbg(rcdu->dev, "%s: group %u free planes mask 0x%02x\n",
+			__func__, index, group_free_planes[index]);
+	}
+
+	/* Reallocate hardware planes for each plane that needs it. */
+	for (i = 0; i < dev->mode_config.num_total_plane; ++i) {
+		struct rcar_du_plane_state *plane_state;
+		struct rcar_du_plane *plane;
+		unsigned int crtc_planes;
+		unsigned int free;
+		int idx;
+
+		if (!state->planes[i])
+			continue;
+
+		plane = to_rcar_plane(state->planes[i]);
+		plane_state = to_rcar_plane_state(state->plane_states[i]);
+
+		dev_dbg(rcdu->dev, "%s: allocating plane (%u,%u)\n", __func__,
+			plane->group->index, plane - plane->group->planes);
+
+		/* Skip planes that are being disabled or don't need to be
+		 * reallocated.
+		 */
+		if (!plane_state->format ||
+		    !rcar_du_plane_needs_realloc(plane, plane_state))
+			continue;
+
+		/* Try to allocate the plane from the free planes currently
+		 * associated with the target CRTC to avoid restarting the CRTC
+		 * group and thus minimize flicker. If it fails fall back to
+		 * allocating from all free planes.
+		 */
+		crtc_planes = to_rcar_crtc(plane_state->state.crtc)->index % 2
+			    ? plane->group->dptsr_planes
+			    : ~plane->group->dptsr_planes;
+		free = group_free_planes[plane->group->index];
+
+		idx = rcar_du_plane_hwalloc(plane, plane_state,
+					    free & crtc_planes);
+		if (idx < 0)
+			idx = rcar_du_plane_hwalloc(plane, plane_state,
+						    free);
+		if (idx < 0) {
+			dev_dbg(rcdu->dev, "%s: no available hardware plane\n",
+				__func__);
+			return idx;
+		}
+
+		dev_dbg(rcdu->dev, "%s: allocated %u hwplanes (index %u)\n",
+			__func__, plane_state->format->planes, idx);
+
+		plane_state->hwindex = idx;
+
+		group_free_planes[plane->group->index] &=
+			~rcar_du_plane_hwmask(plane_state);
+
+		dev_dbg(rcdu->dev, "%s: group %u free planes mask 0x%02x\n",
+			__func__, plane->group->index,
+			group_free_planes[plane->group->index]);
+	}
+
+	return 0;
+}
+
+/* -----------------------------------------------------------------------------
+ * Plane Setup
+ */
+
 #define RCAR_DU_COLORKEY_NONE		(0 << 24)
 #define RCAR_DU_COLORKEY_SOURCE		(1 << 24)
 #define RCAR_DU_COLORKEY_MASK		(1 << 24)
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_plane.h b/drivers/gpu/drm/rcar-du/rcar_du_plane.h
index e24e45828d6a..6a6460dffae4 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_plane.h
+++ b/drivers/gpu/drm/rcar-du/rcar_du_plane.h
@@ -71,6 +71,9 @@ to_rcar_plane_state(struct drm_plane_state *state)
 	return container_of(state, struct rcar_du_plane_state, state);
 }
 
+int rcar_du_atomic_check_planes(struct drm_device *dev,
+				struct drm_atomic_state *state);
+
 int rcar_du_planes_init(struct rcar_du_group *rgrp);
 
 void rcar_du_plane_setup(struct rcar_du_plane *plane);
