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From:   Melissa Wen <melissa.srw@gmail.com>
Date:   Sat, 25 Jul 2020 16:29:35 -0300
Message-ID: <CAJeY4oHzL2q1yRDQweSK5CM5WdHrWqqPVhkNc5DPzP1ayJLw+A@mail.gmail.com>
Subject: Re: [PATCH] drm/vkms: add missing drm_crtc_vblank_put to the get/put
 pair on flush
To:     Daniel Vetter <daniel@ffwll.ch>
Cc:     Sidong Yang <realwakka@gmail.com>,
        Haneen Mohammed <hamohammed.sa@gmail.com>,
        Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>,
        David Airlie <airlied@linux.ie>,
        Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        kernel-usp@googlegroups.com
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On Sat, Jul 25, 2020 at 4:19 PM Melissa Wen <melissa.srw@gmail.com> wrote:
>
> > No, this very first warning continues (only once) :(
> > From here (drm_crtc_vblank_on):
> >         if (atomic_read(&vblank->refcount) != 0 || drm_vblank_offdelay == 0)
> >                 drm_WARN_ON(dev, drm_vblank_enable(dev, pipe));
>
> Sorry, not sure when this warning is triggered.

Again, I just had to look at the trace:
[   52.299388]  drm_get_last_vbltimestamp+0xaa/0xc0 [drm]
[   52.299389]  drm_reset_vblank_timestamp+0x5b/0xd0 [drm]
[   52.299389]  drm_crtc_vblank_on.cold+0x37/0x103 [drm]
[   52.299390]  drm_atomic_helper_commit_modeset_enable

>
> >
> > > But I'm still wondering why after step 3 we don't get -EINVAL from
> > > vblank_get() - after vblank_off() vblank->enabled should be false
> > > again, getting us back to the same state as after 1. Is that not
> > > happening?
> >
> > Yes (sorry if it got confused), we got -EINVAL after setp 3:
> >
> > In step 3, at the end of the 2nd running, we have:
> > atomic_disable
> > --> vblank_off [!vblank->inmodeset + refcount going 0->1 + inmodeset=1]
> > and then in next vblank_get: -EINVAL (!vblank->enabled + refcount ends 1)
> > as in the first step.
> >
> > Melissa
> >
> > > -Daniel
> > >
> > > >
> > > > > >
> > > > > > Thanks
> > > > > > -Sidong
> > > > > >
> > > > > > > > >
> > > > > > > > > >             crtc->state->event = NULL;
> > > > > > > > > >     }
> > > > > > > > > >
> > > > > > > > > > --
> > > > > > > > > > 2.27.0
> > > > > > > > > >
> > > > > > > > >
> > > > > > > > > --
> > > > > > > > > Daniel Vetter
> > > > > > > > > Software Engineer, Intel Corporation
> > > > > > > > > http://blog.ffwll.ch
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > --
> > > > > > > Daniel Vetter
> > > > > > > Software Engineer, Intel Corporation
> > > > > > > http://blog.ffwll.ch
> > > > > > > _______________________________________________
> > > > > > > dri-devel mailing list
> > > > > > > dri-devel@lists.freedesktop.org
> > > > > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> > > > >
> > > > >
> > > > >
> > > > > --
> > > > > Daniel Vetter
> > > > > Software Engineer, Intel Corporation
> > > > > http://blog.ffwll.ch
> > >
> > >
> > >
> > > --
> > > Daniel Vetter
> > > Software Engineer, Intel Corporation
> > > http://blog.ffwll.ch