drm: use monotonic time in drm_calc_vbltimestamp_from_scanoutpos

For measuring duration we want to avoid that our start/end timestamps
jump, so use monotonic instead of real time for that.

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

1 files changed, 12 insertions, 6 deletions

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 44602ef55afc..ef5b5f70735e 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -576,7 +576,8 @@ int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, int crtc,
                                           unsigned flags,
                                           struct drm_crtc *refcrtc)
 {
-        struct timeval stime, raw_time;
+        ktime_t stime, etime, mono_time_offset;
+        struct timeval tv_etime;
         struct drm_display_mode *mode;
         int vbl_status, vtotal, vdisplay;
         int vpos, hpos, i;
@@ -625,13 +626,14 @@ int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, int crtc,
                 preempt_disable();
 
                 /* Get system timestamp before query. */
-                do_gettimeofday(&stime);
+                stime = ktime_get();
 
                 /* Get vertical and horizontal scanout pos. vpos, hpos. */
                 vbl_status = dev->driver->get_scanout_position(dev, crtc, &vpos, &hpos);
 
                 /* Get system timestamp after query. */
-                do_gettimeofday(&raw_time);
+                etime = ktime_get();
+                mono_time_offset = ktime_get_monotonic_offset();
 
                 preempt_enable();
 
@@ -642,7 +644,7 @@ int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, int crtc,
                         return -EIO;
                 }
 
-                duration_ns = timeval_to_ns(&raw_time) - timeval_to_ns(&stime);
+                duration_ns = ktime_to_ns(etime) - ktime_to_ns(stime);
 
                 /* Accept result with <  max_error nsecs timing uncertainty. */
                 if (duration_ns <= (s64) *max_error)
@@ -689,14 +691,18 @@ int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, int crtc,
                 vbl_status |= 0x8;
         }
 
+        etime = ktime_sub(etime, mono_time_offset);
+        /* save this only for debugging purposes */
+        tv_etime = ktime_to_timeval(etime);
         /* Subtract time delta from raw timestamp to get final
          * vblank_time timestamp for end of vblank.
          */
-        *vblank_time = ns_to_timeval(timeval_to_ns(&raw_time) - delta_ns);
+        etime = ktime_sub_ns(etime, delta_ns);
+        *vblank_time = ktime_to_timeval(etime);
 
         DRM_DEBUG("crtc %d : v %d p(%d,%d)@ %ld.%ld -> %ld.%ld [e %d us, %d rep]\n",
                   crtc, (int)vbl_status, hpos, vpos,
-                  (long)raw_time.tv_sec, (long)raw_time.tv_usec,
+                  (long)tv_etime.tv_sec, (long)tv_etime.tv_usec,
                   (long)vblank_time->tv_sec, (long)vblank_time->tv_usec,
                   (int)duration_ns/1000, i);