From 85a7ce67f3ebfd5975ffd1febcabfe4999ca911d Mon Sep 17 00:00:00 2001 From: Daniel Kurtz Date: Thu, 27 Dec 2012 01:01:46 +0000 Subject: [PATCH] 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 Signed-off-by: Dave Airlie --- drivers/gpu/drm/drm_irq.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index 71f8205..38e7992 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); -- 2.7.4