drm/imx: fixes for early vblank event issue, array underflow error

- fix an array underflow error by reordering the range check before the array
   subscript in ipu-prg.
 - make some local functions static in ipuv3-plane.
 - add a missng header for ipu_planes_assign_pre in ipuv3-plane.
 - move arming of the vblank event from atomic_begin to atomic_flush, to avoid
   signalling atomic commit completion to userspace before plane atomic_update
   has finished, due to a race condition that is likely to be hit on i.MX6QP on
   PRE enabled channels.
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Merge tag 'imx-drm-fixes-2018-03-22' of git://git.pengutronix.de/git/pza/linux into drm-fixes

drm/imx: fixes for early vblank event issue, array underflow error

- fix an array underflow error by reordering the range check before the array
  subscript in ipu-prg.
- make some local functions static in ipuv3-plane.
- add a missng header for ipu_planes_assign_pre in ipuv3-plane.
- move arming of the vblank event from atomic_begin to atomic_flush, to avoid
  signalling atomic commit completion to userspace before plane atomic_update
  has finished, due to a race condition that is likely to be hit on i.MX6QP on
  PRE enabled channels.

* tag 'imx-drm-fixes-2018-03-22' of git://git.pengutronix.de/git/pza/linux:
  drm/imx: move arming of the vblank event to atomic_flush
  drm/imx: ipuv3-plane: Include "imx-drm.h" header file
  drm/imx: ipuv3-plane: Make functions static when possible
  gpu: ipu-v3: prg: avoid possible array underflow

drivers/gpu/drm/imx/ipuv3-crtc.c

@@ -225,7 +225,11 @@ static void ipu_crtc_atomic_begin(struct drm_crtc *crtc,
 				  struct drm_crtc_state *old_crtc_state)
 {
 	drm_crtc_vblank_on(crtc);
+}
 
+static void ipu_crtc_atomic_flush(struct drm_crtc *crtc,
+				  struct drm_crtc_state *old_crtc_state)
+{
 	spin_lock_irq(&crtc->dev->event_lock);
 	if (crtc->state->event) {
 		WARN_ON(drm_crtc_vblank_get(crtc));
@@ -293,6 +297,7 @@ static const struct drm_crtc_helper_funcs ipu_helper_funcs = {
 	.mode_set_nofb = ipu_crtc_mode_set_nofb,
 	.atomic_check = ipu_crtc_atomic_check,
 	.atomic_begin = ipu_crtc_atomic_begin,
+	.atomic_flush = ipu_crtc_atomic_flush,
 	.atomic_disable = ipu_crtc_atomic_disable,
 	.atomic_enable = ipu_crtc_atomic_enable,
 };

drivers/gpu/drm/imx/ipuv3-plane.c

@@ -22,6 +22,7 @@
 #include <drm/drm_plane_helper.h>
 
 #include "video/imx-ipu-v3.h"
+#include "imx-drm.h"
 #include "ipuv3-plane.h"
 
 struct ipu_plane_state {
@@ -272,7 +273,7 @@ static void ipu_plane_destroy(struct drm_plane *plane)
 	kfree(ipu_plane);
 }
 
-void ipu_plane_state_reset(struct drm_plane *plane)
+static void ipu_plane_state_reset(struct drm_plane *plane)
 {
 	struct ipu_plane_state *ipu_state;
 
@@ -292,7 +293,8 @@ void ipu_plane_state_reset(struct drm_plane *plane)
 	plane->state = &ipu_state->base;
 }
 
-struct drm_plane_state *ipu_plane_duplicate_state(struct drm_plane *plane)
+static struct drm_plane_state *
+ipu_plane_duplicate_state(struct drm_plane *plane)
 {
 	struct ipu_plane_state *state;
 
@@ -306,8 +308,8 @@ struct drm_plane_state *ipu_plane_duplicate_state(struct drm_plane *plane)
 	return &state->base;
 }
 
-void ipu_plane_destroy_state(struct drm_plane *plane,
-			     struct drm_plane_state *state)
+static void ipu_plane_destroy_state(struct drm_plane *plane,
+				    struct drm_plane_state *state)
 {
 	struct ipu_plane_state *ipu_state = to_ipu_plane_state(state);
 

drivers/gpu/ipu-v3/ipu-prg.c

@@ -250,10 +250,14 @@ void ipu_prg_channel_disable(struct ipuv3_channel *ipu_chan)
 {
 	int prg_chan = ipu_prg_ipu_to_prg_chan(ipu_chan->num);
 	struct ipu_prg *prg = ipu_chan->ipu->prg_priv;
-	struct ipu_prg_channel *chan = &prg->chan[prg_chan];
+	struct ipu_prg_channel *chan;
 	u32 val;
 
-	if (!chan->enabled || prg_chan < 0)
+	if (prg_chan < 0)
+		return;
+
+	chan = &prg->chan[prg_chan];
+	if (!chan->enabled)
 		return;
 
 	pm_runtime_get_sync(prg->dev);
@@ -280,13 +284,15 @@ int ipu_prg_channel_configure(struct ipuv3_channel *ipu_chan,
 {
 	int prg_chan = ipu_prg_ipu_to_prg_chan(ipu_chan->num);
 	struct ipu_prg *prg = ipu_chan->ipu->prg_priv;
-	struct ipu_prg_channel *chan = &prg->chan[prg_chan];
+	struct ipu_prg_channel *chan;
 	u32 val;
 	int ret;
 
 	if (prg_chan < 0)
 		return prg_chan;
 
+	chan = &prg->chan[prg_chan];
+
 	if (chan->enabled) {
 		ipu_pre_update(prg->pres[chan->used_pre], *eba);
 		return 0;