Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20200722110411.ebkv6knvc6mzw5uf@smtp.gmail.com>
 <20200722120502.GK6419@phenom.ffwll.local> <20200722140604.27dfzfnzug5vb75r@smtp.gmail.com>
 <CAKMK7uHWCnJ+3YnP2FwVGH6cEDkmPnH9ALjY_1R51QVs0HPG0Q@mail.gmail.com>
 <20200725011737.GA2851@realwakka> <CAKMK7uEWPCzx+K=+nJsLT5HRBVJ+s8tqx30Ljkr4BCBDComyWQ@mail.gmail.com>
 <20200725174514.esh4gqek6oddizvh@smtp.gmail.com> <CAKMK7uEi0UFSwYTO7h6_YKN+UykOuVcmhMSG_ySy9uyo_7Pz-g@mail.gmail.com>
 <20200725184918.togb54bxuifrq77c@smtp.gmail.com> <CAJeY4oEr1mDASzdjfyeXqfqUmM6n1ULgnedM7dif6db6Qk-r2g@mail.gmail.com>
 <CAJeY4oHzL2q1yRDQweSK5CM5WdHrWqqPVhkNc5DPzP1ayJLw+A@mail.gmail.com>
In-Reply-To: <CAJeY4oHzL2q1yRDQweSK5CM5WdHrWqqPVhkNc5DPzP1ayJLw+A@mail.gmail.com>
From:   Daniel Vetter <daniel@ffwll.ch>
Date:   Sun, 26 Jul 2020 12:26:08 +0200
Message-ID: <CAKMK7uGQXXDhYGOwYdorKECgNW2Ydq=Mxu_Tm-GrOY8SHftB+g@mail.gmail.com>
Subject: Re: [PATCH] drm/vkms: add missing drm_crtc_vblank_put to the get/put
 pair on flush
To:     Melissa Wen <melissa.srw@gmail.com>
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
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Sat, Jul 25, 2020 at 9:29 PM Melissa Wen <melissa.srw@gmail.com> wrote:
>
> 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

Yeah I think vkms can't generate a reasonable timestamp when the
hrtimer is off. I thought the warning comes from a different
callchain, but seems to be a general problem.

I guess in the vkms timestamp function we should check whether the
timer is running, and if it's not running, then we just grab the
current time and done.
-Daniel

> >
> > >
> > > > 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


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch