drm: Add DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE/RELATIVE flags v2

These flags allow userspace to explicitly specify the target vertical
blank period when a flip should take effect.

v2:
* Add new struct drm_mode_crtc_page_flip_target instead of modifying
  struct drm_mode_crtc_page_flip, to make sure all existing userspace
  code keeps compiling (Daniel Vetter)

Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index a316f73..93b9821 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -5398,15 +5398,23 @@
 int drm_mode_page_flip_ioctl(struct drm_device *dev,
 			     void *data, struct drm_file *file_priv)
 {
-	struct drm_mode_crtc_page_flip *page_flip = data;
+	struct drm_mode_crtc_page_flip_target *page_flip = data;
 	struct drm_crtc *crtc;
 	struct drm_framebuffer *fb = NULL;
 	struct drm_pending_vblank_event *e = NULL;
-	u32 target_vblank = 0;
+	u32 target_vblank = page_flip->sequence;
 	int ret = -EINVAL;
 
-	if (page_flip->flags & ~DRM_MODE_PAGE_FLIP_FLAGS ||
-	    page_flip->reserved != 0)
+	if (page_flip->flags & ~DRM_MODE_PAGE_FLIP_FLAGS)
+		return -EINVAL;
+
+	if (page_flip->sequence != 0 && !(page_flip->flags & DRM_MODE_PAGE_FLIP_TARGET))
+		return -EINVAL;
+
+	/* Only one of the DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE/RELATIVE flags
+	 * can be specified
+	 */
+	if ((page_flip->flags & DRM_MODE_PAGE_FLIP_TARGET) == DRM_MODE_PAGE_FLIP_TARGET)
 		return -EINVAL;
 
 	if ((page_flip->flags & DRM_MODE_PAGE_FLIP_ASYNC) && !dev->mode_config.async_page_flip)
@@ -5417,15 +5425,41 @@
 		return -ENOENT;
 
 	if (crtc->funcs->page_flip_target) {
+		u32 current_vblank;
 		int r;
 
 		r = drm_crtc_vblank_get(crtc);
 		if (r)
 			return r;
 
-		target_vblank = drm_crtc_vblank_count(crtc) +
-			!(page_flip->flags & DRM_MODE_PAGE_FLIP_ASYNC);
-	} else if (crtc->funcs->page_flip == NULL) {
+		current_vblank = drm_crtc_vblank_count(crtc);
+
+		switch (page_flip->flags & DRM_MODE_PAGE_FLIP_TARGET) {
+		case DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE:
+			if ((int)(target_vblank - current_vblank) > 1) {
+				DRM_DEBUG("Invalid absolute flip target %u, "
+					  "must be <= %u\n", target_vblank,
+					  current_vblank + 1);
+				drm_crtc_vblank_put(crtc);
+				return -EINVAL;
+			}
+			break;
+		case DRM_MODE_PAGE_FLIP_TARGET_RELATIVE:
+			if (target_vblank != 0 && target_vblank != 1) {
+				DRM_DEBUG("Invalid relative flip target %u, "
+					  "must be 0 or 1\n", target_vblank);
+				drm_crtc_vblank_put(crtc);
+				return -EINVAL;
+			}
+			target_vblank += current_vblank;
+			break;
+		default:
+			target_vblank = current_vblank +
+				!(page_flip->flags & DRM_MODE_PAGE_FLIP_ASYNC);
+			break;
+		}
+	} else if (crtc->funcs->page_flip == NULL ||
+		   (page_flip->flags & DRM_MODE_PAGE_FLIP_TARGET)) {
 		return -EINVAL;
 	}
 
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 33af4a5..0099d2a 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -228,6 +228,7 @@
 static int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
 {
 	struct drm_get_cap *req = data;
+	struct drm_crtc *crtc;
 
 	req->value = 0;
 	switch (req->capability) {
@@ -254,6 +255,13 @@
 	case DRM_CAP_ASYNC_PAGE_FLIP:
 		req->value = dev->mode_config.async_page_flip;
 		break;
+	case DRM_CAP_PAGE_FLIP_TARGET:
+		req->value = 1;
+		drm_for_each_crtc(crtc, dev) {
+			if (!crtc->funcs->page_flip_target)
+				req->value = 0;
+		}
+		break;
 	case DRM_CAP_CURSOR_WIDTH:
 		if (dev->mode_config.cursor_width)
 			req->value = dev->mode_config.cursor_width;