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authorDaniel Kurtz <djkurtz@chromium.org>2012-12-27 05:01:46 +0400
committerDave Airlie <airlied@redhat.com>2013-02-08 08:00:48 +0400
commit85a7ce67f3ebfd5975ffd1febcabfe4999ca911d (patch)
treed98adc99ef6bbccb40bcebdcdbc317bbceca1640 /drivers/gpu/drm/drm_irq.c
parentdd66cc2e1f4765d0e6f39eb1e7d8d64d3f1cc522 (diff)
downloadlinux-85a7ce67f3ebfd5975ffd1febcabfe4999ca911d.tar.xz
drm: make frame duration time calculation more precise
It is a bit more precise to compute the total number of pixels first and then divide, rather than multiplying the line pixel count by the already-rounded line duration. Signed-off-by: Daniel Kurtz <djkurtz@chromium.org> Signed-off-by: Dave Airlie <airlied@redhat.com>
Diffstat (limited to 'drivers/gpu/drm/drm_irq.c')
-rw-r--r--drivers/gpu/drm/drm_irq.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 71f820565637..38e79927b2d7 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -505,6 +505,7 @@ void drm_calc_timestamping_constants(struct drm_crtc *crtc)
/* Valid dotclock? */
if (dotclock > 0) {
+ int frame_size;
/* Convert scanline length in pixels and video dot clock to
* line duration, frame duration and pixel duration in
* nanoseconds:
@@ -512,7 +513,10 @@ void drm_calc_timestamping_constants(struct drm_crtc *crtc)
pixeldur_ns = (s64) div64_u64(1000000000, dotclock);
linedur_ns = (s64) div64_u64(((u64) crtc->hwmode.crtc_htotal *
1000000000), dotclock);
- framedur_ns = (s64) crtc->hwmode.crtc_vtotal * linedur_ns;
+ frame_size = crtc->hwmode.crtc_htotal *
+ crtc->hwmode.crtc_vtotal;
+ framedur_ns = (s64) div64_u64((u64) frame_size * 1000000000,
+ dotclock);
} else
DRM_ERROR("crtc %d: Can't calculate constants, dotclock = 0!\n",
crtc->base.id);