Re: [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