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SubjectRe: [PATCH] drm: make frame duration time calculation more precise
On Wed, Dec 26, 2012 at 5:01 PM, Daniel Kurtz <djkurtz@chromium.org> wrote:
>
> 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>

Ping?

> ---
> drivers/gpu/drm/drm_irq.c | 6 +++++-
> 1 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index 19c01ca..05c91e0 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);
> --
> 1.7.7.3
>


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