drm/virtio: Don't reinvent a flipping wheel

Now that the core helpers support nonblocking atomic commits there's
no need to invent that wheel separately (instead of fixing the bug in
the atomic implementation of virtio, as it should have been done!).

v2: Rebased on top of

commit e7cf0963f816fa44190caaf51aeffaa614c340c6
Author: Gerd Hoffmann <[e-mail]>
Date: Tue May 31 08:50:47 2016 +0200

virtio-gpu: add atomic_commit function

Cc: Gerd Hoffmann <[e-mail]>
Tested-by: Gerd Hoffmann <[e-mail]>
Reviewed-by: Gerd Hoffmann <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/virtio/virtgpu_display.c

···
 #define XRES_MAX  8192
 #define YRES_MAX  8192
 
-static int virtio_gpu_page_flip(struct drm_crtc *crtc,
-				struct drm_framebuffer *fb,
-				struct drm_pending_vblank_event *event,
-				uint32_t flags)
-{
-	struct virtio_gpu_device *vgdev = crtc->dev->dev_private;
-	struct virtio_gpu_output *output =
-		container_of(crtc, struct virtio_gpu_output, crtc);
-	struct drm_plane *plane = crtc->primary;
-	struct virtio_gpu_framebuffer *vgfb;
-	struct virtio_gpu_object *bo;
-	unsigned long irqflags;
-	uint32_t handle;
-
-	plane->fb = fb;
-	vgfb = to_virtio_gpu_framebuffer(plane->fb);
-	bo = gem_to_virtio_gpu_obj(vgfb->obj);
-	handle = bo->hw_res_handle;
-
-	DRM_DEBUG("handle 0x%x%s, crtc %dx%d\n", handle,
-		  bo->dumb ? ", dumb" : "",
-		  crtc->mode.hdisplay, crtc->mode.vdisplay);
-	if (bo->dumb) {
-		virtio_gpu_cmd_transfer_to_host_2d
-			(vgdev, handle, 0,
-			 cpu_to_le32(crtc->mode.hdisplay),
-			 cpu_to_le32(crtc->mode.vdisplay),
-			 0, 0, NULL);
-	}
-	virtio_gpu_cmd_set_scanout(vgdev, output->index, handle,
-				   crtc->mode.hdisplay,
-				   crtc->mode.vdisplay, 0, 0);
-	virtio_gpu_cmd_resource_flush(vgdev, handle, 0, 0,
-				      crtc->mode.hdisplay,
-				      crtc->mode.vdisplay);
-
-	if (event) {
-		spin_lock_irqsave(&crtc->dev->event_lock, irqflags);
-		drm_crtc_send_vblank_event(crtc, event);
-		spin_unlock_irqrestore(&crtc->dev->event_lock, irqflags);
-	}
-
-	return 0;
-}
-
 static const struct drm_crtc_funcs virtio_gpu_crtc_funcs = {
 	.set_config             = drm_atomic_helper_set_config,
 	.destroy                = drm_crtc_cleanup,
 
-	.page_flip              = virtio_gpu_page_flip,
+	.page_flip              = drm_atomic_helper_page_flip,
 	.reset                  = drm_atomic_helper_crtc_reset,
 	.atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
 	.atomic_destroy_state   = drm_atomic_helper_crtc_destroy_state,
···
 	spin_lock_irqsave(&crtc->dev->event_lock, flags);
 	if (crtc->state->event)
 		drm_crtc_send_vblank_event(crtc, crtc->state->event);
+	crtc->state->event = NULL;
 	spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
 }
 
···
 	return &virtio_gpu_fb->base;
 }
 
-static int vgdev_atomic_commit(struct drm_device *dev,
-			       struct drm_atomic_state *state,
-			       bool nonblock)
+static void vgdev_atomic_commit_tail(struct drm_atomic_state *state)
 {
-	if (nonblock)
-		return -EBUSY;
-
-	drm_atomic_helper_swap_state(state, true);
-	drm_atomic_helper_wait_for_fences(dev, state);
+	struct drm_device *dev = state->dev;
 
 	drm_atomic_helper_commit_modeset_disables(dev, state);
 	drm_atomic_helper_commit_modeset_enables(dev, state);
 	drm_atomic_helper_commit_planes(dev, state, true);
 
+	drm_atomic_helper_commit_hw_done(state);
+
 	drm_atomic_helper_wait_for_vblanks(dev, state);
 	drm_atomic_helper_cleanup_planes(dev, state);
-	drm_atomic_state_free(state);
-	return 0;
 }
+
+struct drm_mode_config_helper_funcs virtio_mode_config_helpers = {
+	.atomic_commit_tail = vgdev_atomic_commit_tail,
+};
 
 static const struct drm_mode_config_funcs virtio_gpu_mode_funcs = {
 	.fb_create = virtio_gpu_user_framebuffer_create,
 	.atomic_check = drm_atomic_helper_check,
-	.atomic_commit = vgdev_atomic_commit,
+	.atomic_commit = drm_atomic_helper_commit,
 };
 
 int virtio_gpu_modeset_init(struct virtio_gpu_device *vgdev)
···
 	int i;
 
 	drm_mode_config_init(vgdev->ddev);
-	vgdev->ddev->mode_config.funcs = (void *)&virtio_gpu_mode_funcs;
+	vgdev->ddev->mode_config.funcs = &virtio_gpu_mode_funcs;
+	vgdev->ddev->mode_config.helper_private = &virtio_mode_config_helpers;
 
 	/* modes will be validated against the framebuffer size */
 	vgdev->ddev->mode_config.min_width = XRES_MIN;