linux-kernel - Re: [PATCH] DRM: UDL: get rid of useless vblank initialization

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Date:   Tue, 23 Oct 2018 15:42:02 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Eugeniy Paltsev <eugeniy.paltsev@...opsys.com>
Cc:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "daniel.vetter@...ll.ch" <daniel.vetter@...ll.ch>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "marcheu@...omium.org" <marcheu@...omium.org>,
        Alexey Brodkin <alexey.brodkin@...opsys.com>,
        "maarten.lankhorst@...ux.intel.com" 
        <maarten.lankhorst@...ux.intel.com>,
        "gustavo@...ovan.org" <gustavo@...ovan.org>,
        "sean@...rly.run" <sean@...rly.run>
Subject: Re: [PATCH] DRM: UDL: get rid of useless vblank initialization

On Tue, Oct 23, 2018 at 11:01:14AM +0000, Eugeniy Paltsev wrote:
> Hi David,
> 
> Maybe you have any comments or remarks about this patch?
> And if you don't could you please apply it. Thanks!

Hm I hoped Sean would pick this up. I stuffed it into drm-misc-next now,
and Sean owes me one. Generally pinging Dave is a last resort in dri-devel
(and doesn't work too well).

Thanks for your patch.
-Daniel
> 
> On Fri, 2018-09-28 at 17:41 +0300, Eugeniy Paltsev wrote:
> > UDL doesn't support vblank functionality so we don't need to
> > initialize vblank here (we are able to send page flip
> > completion events even without vblank initialization)
> > 
> > Moreover current drm_vblank_init call with num_crtcs > 0 causes
> > sending DRM_EVENT_FLIP_COMPLETE event with zero timestamp every
> > time. This breaks userspace apps (for example weston) which
> > relies on timestamp value.
> > 
> > Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> > ---
> >  drivers/gpu/drm/udl/udl_main.c | 7 +------
> >  1 file changed, 1 insertion(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/udl/udl_main.c b/drivers/gpu/drm/udl/udl_main.c
> > index f455f095a146..1b014d92855b 100644
> > --- a/drivers/gpu/drm/udl/udl_main.c
> > +++ b/drivers/gpu/drm/udl/udl_main.c
> > @@ -350,15 +350,10 @@ int udl_driver_load(struct drm_device *dev, unsigned long flags)
> >  	if (ret)
> >  		goto err;
> >  
> > -	ret = drm_vblank_init(dev, 1);
> > -	if (ret)
> > -		goto err_fb;
> > -
> >  	drm_kms_helper_poll_init(dev);
> >  
> >  	return 0;
> > -err_fb:
> > -	udl_fbdev_cleanup(dev);
> > +
> >  err:
> >  	if (udl->urbs.count)
> >  		udl_free_urb_list(dev);
> -- 
>  Eugeniy Paltsev

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