If scanout started, we should reduce etime by delta_ns. But delta_ns is negative if scanout has not started. If delta_ns is negative, subtraction of delta_ns from etime increases etime. This is wrong, the etime should not be increased, so you have to make delta_ns an absolute value.
Signed-off-by: Hoegeun Kwon hoegeun.kwon@samsung.com ---
Hello all,
I think that the etime should not be increased. In cases where delta_ns is negative, if you get time again after an interrupt call, there is a problem that the time obtained from the interrupt becomes the future time instead of the past time.
Please let me know if this patch is wrong.
Best regards, Hoegeun
drivers/gpu/drm/drm_vblank.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 70f2b95..a3e0176 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -684,7 +684,7 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, /* Subtract time delta from raw timestamp to get final * vblank_time timestamp for end of vblank. */ - etime = ktime_sub_ns(etime, delta_ns); + etime = ktime_sub_ns(etime, abs(delta_ns)); *vblank_time = ktime_to_timeval(etime);
DRM_DEBUG_VBL("crtc %u : v p(%d,%d)@ %ld.%ld -> %ld.%ld [e %d us, %d rep]\n",