Re: [PATCH 03/27] drm/arc: Actually bother with handling atomic events.

[Alexey Brodkin <Alexey.Brodkin@synopsys.com>]

Hi Daniel,

On Wed, 2016-06-08 at 16:30 +0200, Daniel Vetter wrote:
> On Wed, Jun 08, 2016 at 04:14:38PM +0200, Maarten Lankhorst wrote:
> > 
> > Op 08-06-16 om 14:18 schreef Daniel Vetter:
> > > 
> > > The drm core has a nice ready-made helper for exactly the simple case
> > > where it should fire on the next vblank.
> > > 
> > > Note that arming the vblank event in _begin is probably too early, and
> > > might easily result in the vblank firing too early, before the new set
> > > of planes are actually disabled. But that's kinda a minor issue
> > > compared to just outright hanging userspace.
> > > 
> > > v2: Be more robust and either arm, when the CRTC is on, or just send
> > > the event out right away.
> > > 
> > > Cc: Carlos Palminha <palminha@synopsys.com>
> > > Cc: Alexey Brodkin <abrodkin@synopsys.com>
> > > Cc: linux-snps-arc@lists.infradead.org
> > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > Wouldn't it be better to do this in atomic_flush then?
> I'm not going to fix up other people's drivers completely, just enough to
> hopefully not break them. If arc also blocks vblank interrupts with the go
> bit, then doing this in _begin is correct. Either way it needs hw-specific
> knowledge to asses whether it's correct, since doing the vblank event
> stuff in _flush is also racy without some prevention.

Actually in ARC PGU driver that was one of many other copy-pastes from
other drivers. I.e. for me this is another boilerplate and if that's the
same for other drivers as well probably that's a good candidate for
generalization into something like drm_helper_crtc_atomic_check().

-Alexey
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