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 <[e-mail]>
Reviewed-by: Daniel Vetter <[e-mail]>
Signed-off-by: Michel Dänzer <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/drm_crtc.c

···
 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)
···
 		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;
 	}
 

drivers/gpu/drm/drm_ioctl.c

···
 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) {
···
 		break;
 	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)

include/uapi/drm/drm.h

···
 #define DRM_CAP_CURSOR_WIDTH		0x8
 #define DRM_CAP_CURSOR_HEIGHT		0x9
 #define DRM_CAP_ADDFB2_MODIFIERS	0x10
+#define DRM_CAP_PAGE_FLIP_TARGET	0x11
 
 /** DRM_IOCTL_GET_CAP ioctl argument type */
 struct drm_get_cap {

include/uapi/drm/drm_mode.h

···
 
 #define DRM_MODE_PAGE_FLIP_EVENT 0x01
 #define DRM_MODE_PAGE_FLIP_ASYNC 0x02
-#define DRM_MODE_PAGE_FLIP_FLAGS (DRM_MODE_PAGE_FLIP_EVENT|DRM_MODE_PAGE_FLIP_ASYNC)
+#define DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE 0x4
+#define DRM_MODE_PAGE_FLIP_TARGET_RELATIVE 0x8
+#define DRM_MODE_PAGE_FLIP_TARGET (DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE | \
+				   DRM_MODE_PAGE_FLIP_TARGET_RELATIVE)
+#define DRM_MODE_PAGE_FLIP_FLAGS (DRM_MODE_PAGE_FLIP_EVENT | \
+				  DRM_MODE_PAGE_FLIP_ASYNC | \
+				  DRM_MODE_PAGE_FLIP_TARGET)
 
 /*
  * Request a page flip on the specified crtc.
···
  * 'as soon as possible', meaning that it not delay waiting for vblank.
  * This may cause tearing on the screen.
  *
- * The reserved field must be zero until we figure out something
- * clever to use it for.
+ * The reserved field must be zero.
  */
 
 struct drm_mode_crtc_page_flip {
···
 	__u32 fb_id;
 	__u32 flags;
 	__u32 reserved;
+	__u64 user_data;
+};
+
+/*
+ * Request a page flip on the specified crtc.
+ *
+ * Same as struct drm_mode_crtc_page_flip, but supports new flags and
+ * re-purposes the reserved field:
+ *
+ * The sequence field must be zero unless either of the
+ * DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE/RELATIVE flags is specified. When
+ * the ABSOLUTE flag is specified, the sequence field denotes the absolute
+ * vblank sequence when the flip should take effect. When the RELATIVE
+ * flag is specified, the sequence field denotes the relative (to the
+ * current one when the ioctl is called) vblank sequence when the flip
+ * should take effect. NOTE: DRM_IOCTL_WAIT_VBLANK must still be used to
+ * make sure the vblank sequence before the target one has passed before
+ * calling this ioctl. The purpose of the
+ * DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE/RELATIVE flags is merely to clarify
+ * the target for when code dealing with a page flip runs during a
+ * vertical blank period.
+ */
+
+struct drm_mode_crtc_page_flip_target {
+	__u32 crtc_id;
+	__u32 fb_id;
+	__u32 flags;
+	__u32 sequence;
 	__u64 user_data;
 };