On 01/30, Shayenne Moura wrote: > kms_flip tests are breaking on vkms when simulate vblank because vblank > event sequence count returns one extra frame after arm vblank event to > make a page flip. > > When vblank interrupt happens, userspace processes the vblank event and > issues the next page flip command. Kernel calls queue_work to call > commit_planes and arm the new page flip. The next vblank picks up the > newly armed vblank event and vblank interrupt happens again. > > The arm and vblank event are asynchronous, then, on the next vblank, we > receive x+2 from `get_vblank_timestamp`, instead x+1, although timestamp > and vblank seqno matches. > > Function `get_vblank_timestamp` is reached by 2 ways: > > - from `drm_mode_page_flip_ioctl`: driver is doing one atomic operation > to synchronize planes in the same output. There is no vblank simulation, > the `drm_crtc_arm_vblank_event` function adds 1 on vblank count, and the > variable in_vblank_irq is false > - from `vkms_vblank_simulate`: since the driver is doing a vblank simulation, > the variable in_vblank_irq is true. > > Fix this problem subtracting one vblank period from vblank_time when > `get_vblank_timestamp` is called from trace `drm_mode_page_flip_ioctl`, > i.e., is not a real vblank interrupt, and getting the timestamp and vblank > seqno when it is a real vblank interrupt. > > The reason for all this is that get_vblank_timestamp always supplies the > timestamp for the next vblank event. The hrtimer is the vblank simulator, > and it needs the correct previous value to present the next vblank. Since > this is how hw timestamp registers work and what the vblank core expects. > > Signed-off-by: Shayenne Moura <shayenneluzmoura@xxxxxxxxx> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > > --- > drivers/gpu/drm/vkms/vkms_crtc.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c > index d44bfc392491..23146ff2a25b 100644 > --- a/drivers/gpu/drm/vkms/vkms_crtc.c > +++ b/drivers/gpu/drm/vkms/vkms_crtc.c > @@ -87,6 +87,9 @@ bool vkms_get_vblank_timestamp(struct drm_device *dev, unsigned int pipe, > > *vblank_time = output->vblank_hrtimer.node.expires; > > + if (!in_vblank_irq) > + *vblank_time -= output->period_ns; > + > return true; > } > > -- > 2.17.1 > Reviewed-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx> -- Rodrigo Siqueira https://siqueira.tech Graduate Student Department of Computer Science University of São Paulo
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