drm: add support for monotonic vblank timestamps

Jumps in the vblank and page flip event timestamps cause trouble for
clients, so we should avoid them. The timestamp we get currently with
gettimeofday can jump, so use instead monotonic timestamps.

For backward compatibility use a module flag to revert back to using
gettimeofday timestamps. Add also a DRM_CAP_TIMESTAMP_MONOTONIC flag
that is simply a read only version of the module flag, so that clients
can query this without depending on sysfs.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 29eb23799aa4..fad21c927a38 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1505,6 +1505,7 @@ extern unsigned int drm_debug;
 
 extern unsigned int drm_vblank_offdelay;
 extern unsigned int drm_timestamp_precision;
+extern unsigned int drm_timestamp_monotonic;
 
 extern struct class *drm_class;
 extern struct proc_dir_entry *drm_proc_root;