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drm/nouveau: fix small thinko in vblank timestamping. 

*hpos horizontal scanout position doesn't need to be corrected
to count the pixels between hactive end and htotal negative.
That is only needed for *vpos to count lines until end of
vblank for the vblank timestamping.

Use hpos as is without correction.

Removes occassional spikes in timestamps of up to 1 scanline
duration, thereby improves accuracy to about +/- 2 usecs instead
of +/- 12 usecs, wrt. true onset time as measured with high
precision equipment on NV-A5.

Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
This commit is contained in:
Mario Kleiner 2014-03-19 10:02:11 +01:00 committed by Ben Skeggs
parent dcd9262b3b
commit 6c3252bc83
1 changed files with 1 additions and 1 deletions
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2
drivers/gpu/drm/nouveau/nouveau_display.c
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@ -105,7 +105,7 @@ nouveau_display_scanoutpos_head(struct drm_crtc *crtc, int *vpos, int *hpos,
if (retry) ndelay(crtc->linedur_ns);
} while (retry--);
*hpos = calc(args.hblanks, args.hblanke, args.htotal, args.hline);
*hpos = args.hline;
*vpos = calc(args.vblanks, args.vblanke, args.vtotal, args.vline);
if (stime) *stime = ns_to_ktime(args.time[0]);
if (etime) *etime = ns_to_ktime(args.time[1]);