Merge branch 'drm/tegra-for-3.9' of git://anongit.freedesktop.org/teg…

…ra/linux into drm-next

Thierry writes:
"Add support for 2 hardware overlays found on Tegra. These support YUV
pixel formats and can be used as video overlays. .mode_set_base() is
implemented and support for VBLANK and page-flipping is added.

A few minor bug fixes are also included and a new debugfs file allows
to inspect the framebuffers attached to the Tegra DRM device."

* 'drm/tegra-for-3.9' of git://anongit.freedesktop.org/tegra/linux:
  drm/tegra: Add list of framebuffers to debugfs
  drm/tegra: Fix color expansion
  drm/tegra: Split DC_CMD_STATE_CONTROL register write
  drm/tegra: Implement page-flipping support
  drm/tegra: Implement VBLANK support
  drm/tegra: Implement .mode_set_base()
  drm/tegra: Add plane support
  drm/tegra: Remove bogus tegra_framebuffer structure
  drm: Add consistency check for page-flipping

Documentation/DocBook/drm.tmpl

@@ -1160,6 +1160,12 @@ int max_width, max_height;</synopsis>
             without waiting for rendering or page flip to complete and must block
             any new rendering to the frame buffer until the page flip completes.
           </para>
+          <para>
+            If a page flip can be successfully scheduled the driver must set the
+            <code>drm_crtc-&lt;fb</code> field to the new framebuffer pointed to
+            by <code>fb</code>. This is important so that the reference counting
+            on framebuffers stays balanced.
+          </para>
           <para>
             If a page flip is already pending, the
             <methodname>page_flip</methodname> operation must return

drivers/gpu/drm/drm_crtc.c

@@ -3792,6 +3792,13 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 		/* Keep the old fb, don't unref it. */
 		old_fb = NULL;
 	} else {
+		/*
+		 * Warn if the driver hasn't properly updated the crtc->fb
+		 * field to reflect that the new framebuffer is now used.
+		 * Failing to do so will screw with the reference counting
+		 * on framebuffers.
+		 */
+		WARN_ON(crtc->fb != fb);
 		/* Unref only the old framebuffer. */
 		fb = NULL;
 	}