drm/mediatek: Use drm_atomic_helper_wait_for_fences

If we use the gem fb helper as the prepare_fb hook, plus the
drm_prime.c import helpers now automatically setting obj->resv, we can
use the shared helpers to wait for fences instead of rolling our own.
Note that this relies on mtk setting drm_fb->obj, which is already
done in mtk_drm_framebuffer_init().

Aside: Probably can use the default commit_tail with this again, but I
didn't check for that.
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: CK Hu <ck.hu@mediatek.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mediatek@lists.infradead.org
Link: https://patchwork.freedesktop.org/patch/msgid/20190614203615.12639-45-daniel.vetter@ffwll.ch

drivers/gpu/drm/mediatek/mtk_drm_drv.c

@@ -38,22 +38,12 @@ static void mtk_atomic_schedule(struct mtk_drm_private *private,
 	schedule_work(&private->commit.work);
 }
 
-static void mtk_atomic_wait_for_fences(struct drm_atomic_state *state)
-{
-	struct drm_plane *plane;
-	struct drm_plane_state *new_plane_state;
-	int i;
-
-	for_each_new_plane_in_state(state, plane, new_plane_state, i)
-		mtk_fb_wait(new_plane_state->fb);
-}
-
 static void mtk_atomic_complete(struct mtk_drm_private *private,
 				struct drm_atomic_state *state)
 {
 	struct drm_device *drm = private->drm;
 
-	mtk_atomic_wait_for_fences(state);
+	drm_atomic_helper_wait_for_fences(drm, state, false);
 
 	/*
 	 * Mediatek drm supports runtime PM, so plane registers cannot be

drivers/gpu/drm/mediatek/mtk_drm_fb.c

@@ -49,34 +49,6 @@ static struct drm_framebuffer *mtk_drm_framebuffer_init(struct drm_device *dev,
 	return fb;
 }
 
-/*
- * Wait for any exclusive fence in fb's gem object's reservation object.
- *
- * Returns -ERESTARTSYS if interrupted, else 0.
- */
-int mtk_fb_wait(struct drm_framebuffer *fb)
-{
-	struct drm_gem_object *gem;
-	struct reservation_object *resv;
-	long ret;
-
-	if (!fb)
-		return 0;
-
-	gem = fb->obj[0];
-	if (!gem || !gem->dma_buf || !gem->dma_buf->resv)
-		return 0;
-
-	resv = gem->dma_buf->resv;
-	ret = reservation_object_wait_timeout_rcu(resv, false, true,
-						  MAX_SCHEDULE_TIMEOUT);
-	/* MAX_SCHEDULE_TIMEOUT on success, -ERESTARTSYS if interrupted */
-	if (WARN_ON(ret < 0))
-		return ret;
-
-	return 0;
-}
-
 struct drm_framebuffer *mtk_drm_mode_fb_create(struct drm_device *dev,
 					       struct drm_file *file,
 					       const struct drm_mode_fb_cmd2 *cmd)

drivers/gpu/drm/mediatek/mtk_drm_fb.h

@@ -6,7 +6,6 @@
 #ifndef MTK_DRM_FB_H
 #define MTK_DRM_FB_H
 
-int mtk_fb_wait(struct drm_framebuffer *fb);
 struct drm_framebuffer *mtk_drm_mode_fb_create(struct drm_device *dev,
 					       struct drm_file *file,
 					       const struct drm_mode_fb_cmd2 *cmd);

drivers/gpu/drm/mediatek/mtk_drm_plane.c

@@ -8,6 +8,7 @@
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_plane_helper.h>
+#include <drm/drm_gem_framebuffer_helper.h>
 
 #include "mtk_drm_crtc.h"
 #include "mtk_drm_ddp_comp.h"
@@ -146,6 +147,7 @@ static void mtk_plane_atomic_disable(struct drm_plane *plane,
 }
 
 static const struct drm_plane_helper_funcs mtk_plane_helper_funcs = {
+	.prepare_fb = drm_gem_fb_prepare_fb,
 	.atomic_check = mtk_plane_atomic_check,
 	.atomic_update = mtk_plane_atomic_update,
 	.atomic_disable = mtk_plane_atomic_disable,