drm/radeon/kms: implement timestamp userspace query (v2)

Returns a snapshot of the GPU clock counter.  Needed
for certain OpenGL extensions.

v2: agd5f
- address Jerome's comments
- add function documentation

Signed-off-by: Marek Olšák <maraeo@gmail.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/include/drm/radeon_drm.h b/include/drm/radeon_drm.h
index 5805686..dc3a8cd 100644
--- a/include/drm/radeon_drm.h
+++ b/include/drm/radeon_drm.h
@@ -964,6 +964,8 @@
 #define RADEON_INFO_IB_VM_MAX_SIZE	0x0f
 /* max pipes - needed for compute shaders */
 #define RADEON_INFO_MAX_PIPES		0x10
+/* timestamp for GL_ARB_timer_query (OpenGL), returns the current GPU clock */
+#define RADEON_INFO_TIMESTAMP		0x11
 
 struct drm_radeon_info {
 	uint32_t		request;