drm/msm: add support for "stolen" mem

Add support to use the VRAM carveout (if specified in dtb) for fbdev
scanout buffer.  This allows drm/msm to take over a bootloader splash-
screen, and avoids corruption on screen that results if the kernel uses
memory that is still being scanned out for itself.

Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_gem.h

@@ -21,6 +21,9 @@
 #include <linux/reservation.h>
 #include "msm_drv.h"
 
+/* Additional internal-use only BO flags: */
+#define MSM_BO_STOLEN        0x10000000    /* try to use stolen/splash memory */
+
 struct msm_gem_object {
 	struct drm_gem_object base;
 
@@ -59,7 +62,7 @@ struct msm_gem_object {
 	struct reservation_object _resv;
 
 	/* For physically contiguous buffers.  Used when we don't have
-	 * an IOMMU.
+	 * an IOMMU.  Also used for stolen/splashscreen buffer.
 	 */
 	struct drm_mm_node *vram_node;
 };