drm/radeon: Use direct mapping for fast fb access on RS690

This patch allows the CPU to map the stolen vram segment
directly rather than going through the PCI BAR.  This
significantly improves performance for certain workloads with
a properly patched ddx.

Use radeon.fastfb=1 to enable it (disabled by default).
Currently only supported on RS690, but support for RS780/880
and newer APUs may be added eventually.

Signed-off-by: Samuel Li <samuel.li@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/uapi/drm/radeon_drm.h b/include/uapi/drm/radeon_drm.h
index eeda91774c8a..6fd25563f301 100644
--- a/include/uapi/drm/radeon_drm.h
+++ b/include/uapi/drm/radeon_drm.h
@@ -972,6 +972,9 @@ struct drm_radeon_cs {
 #define RADEON_INFO_MAX_SE              0x12
 /* max SH per SE */
 #define RADEON_INFO_MAX_SH_PER_SE       0x13
+/* fast fb access is enabled */
+#define RADEON_INFO_FASTFB_WORKING      0x14
+
 
 struct drm_radeon_info {
         uint32_t                request;