linux-kernel - Re: [PATCH] drm/vkms: Solve bug on kms_crc

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Message-ID: <20190228101412.GM2665@phenom.ffwll.local>
Date:   Thu, 28 Feb 2019 11:14:12 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Shayenne Moura <shayenneluzmoura@...il.com>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>
Cc:     Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>,
        Haneen Mohammed <hamohammed.sa@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/vkms: Solve bug on kms_crc_cursor tests

On Thu, Feb 28, 2019 at 11:11:07AM +0100, Daniel Vetter wrote:
> On Mon, Feb 25, 2019 at 11:26:06AM -0300, Shayenne Moura wrote:
> > vkms_crc_work_handle needs the value of the actual frame to
> > schedule the workqueue that calls periodically the vblank
> > handler and the destroy state functions. However, the frame
> > value returned from vkms_vblank_simulate is updated and
> > diminished in vblank_get_timestamp because it is not in a
> > vblank interrupt, and return an inaccurate value.
> > 
> > Solve this getting the actual vblank frame directly from the
> > vblank->count inside the `struct drm_crtc`, instead of using
> > the `drm_accurate_vblank_count` function.
> > 
> > Signed-off-by: Shayenne Moura <shayenneluzmoura@...il.com>
> 
> Sorry for the delay, I'm a bit swamped right now :-/
> 
> Debug work you're doing here is really impressive! But I have no idea
> what's going on. It doesn't look like it's just papering over a bug (like
> the in_vblank_irq check we've discussed on irc), but I also have no idea
> why it works.
> 
> I'll pull in Ville, he understands this better than me.

Works better if I actually add Ville ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch