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Date:   Mon, 17 Aug 2020 11:03:42 +0200
From:   Gerd Hoffmann <kraxel@redhat.com>
To:     dri-devel@lists.freedesktop.org, 1882851@bugs.launchpad.net,
        David Airlie <airlied@linux.ie>, Chia-I Wu <olvaffe@gmail.com>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@lists.linux-foundation.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] drm/virtio: fix unblank
Message-ID: <20200817090342.bemmtkvz4seayp2i@sirius.home.kraxel.org>
References: <20200807105429.24208-1-kraxel@redhat.com>
 <20200807130956.GE2352366@phenom.ffwll.local>
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  Hi,

> > --- a/drivers/gpu/drm/virtio/virtgpu_display.c
> > +++ b/drivers/gpu/drm/virtio/virtgpu_display.c
> > @@ -100,6 +100,7 @@ static void virtio_gpu_crtc_atomic_enable(struct drm_crtc *crtc,
> >  	struct virtio_gpu_output *output = drm_crtc_to_virtio_gpu_output(crtc);
> >  
> >  	output->enabled = true;
> > +	output->need_update = true;

> > --- a/drivers/gpu/drm/virtio/virtgpu_plane.c
> > +++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
> > @@ -163,7 +163,8 @@ static void virtio_gpu_primary_plane_update(struct drm_plane *plane,
> >  	    plane->state->src_w != old_state->src_w ||
> >  	    plane->state->src_h != old_state->src_h ||
> >  	    plane->state->src_x != old_state->src_x ||
> > -	    plane->state->src_y != old_state->src_y) {
> > +	    plane->state->src_y != old_state->src_y ||
> > +	    output->need_update) {
> 
> Uh instead of hand-rolling what's essentially a drm_crtc_needs_modeset
> check, why not use that one? atomic helpers try to keep the usual suspects
> for state transitions already handy, to avoid every driver rolling their
> own. Or do I miss something here?

Well, the virtio-gpu virtual hardware can't do plane updates and crtc
updates independant from each other.  So the crtc callbacks handle
disable only (we don't need a fb for that) and leave the enable to the
plane update.

I suspect calling drm_atomic_crtc_needs_modeset() in plane update isn't
going to fly ...

take care,
  Gerd