drm: Stop using linedur_ns and pixeldur_ns for vblank timestamps

linedur_ns, and especially pixeldur_ns are becoming rather inaccurate
to be used for the vblank timestamp correction. With 4k@60 the pixel
duration is already below 2ns, so the amount of error due to the
truncation to nanoseconds is introducing quite a bit of error.

We can avoid such problems if we instead calculate the timestamp
delta_ns directly from the dislay timings, avoiding the use of
these intermediate truncated values.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
[danvet: Squash in fixup from Thierry Reding for amdgpu.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 6 insertions, 5 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
index e3d70772b531..9b34a3410c32 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
@@ -745,7 +745,8 @@ bool amdgpu_crtc_scaling_mode_fixup(struct drm_crtc *crtc,
  *
  */
 int amdgpu_get_crtc_scanoutpos(struct drm_device *dev, int crtc, unsigned int flags,
-                               int *vpos, int *hpos, ktime_t *stime, ktime_t *etime)
+                               int *vpos, int *hpos, ktime_t *stime, ktime_t *etime,
+                               const struct drm_display_mode *mode)
 {
         u32 vbl = 0, position = 0;
         int vbl_start, vbl_end, vtotal, ret = 0;
@@ -781,7 +782,7 @@ int amdgpu_get_crtc_scanoutpos(struct drm_device *dev, int crtc, unsigned int fl
         }
         else {
                 /* No: Fake something reasonable which gives at least ok results. */
-                vbl_start = adev->mode_info.crtcs[crtc]->base.hwmode.crtc_vdisplay;
+                vbl_start = mode->crtc_vdisplay;
                 vbl_end = 0;
         }
 
@@ -797,7 +798,7 @@ int amdgpu_get_crtc_scanoutpos(struct drm_device *dev, int crtc, unsigned int fl
 
         /* Inside "upper part" of vblank area? Apply corrective offset if so: */
         if (in_vbl && (*vpos >= vbl_start)) {
-                vtotal = adev->mode_info.crtcs[crtc]->base.hwmode.crtc_vtotal;
+                vtotal = mode->crtc_vtotal;
                 *vpos = *vpos - vtotal;
         }
 
@@ -819,8 +820,8 @@ int amdgpu_get_crtc_scanoutpos(struct drm_device *dev, int crtc, unsigned int fl
          * We only do this if DRM_CALLED_FROM_VBLIRQ.
          */
         if ((flags & DRM_CALLED_FROM_VBLIRQ) && !in_vbl) {
-                vbl_start = adev->mode_info.crtcs[crtc]->base.hwmode.crtc_vdisplay;
-                vtotal = adev->mode_info.crtcs[crtc]->base.hwmode.crtc_vtotal;
+                vbl_start = mode->crtc_vdisplay;
+                vtotal = mode->crtc_vtotal;
 
                 if (vbl_start - *vpos < vtotal / 100) {
                         *vpos -= vtotal;