Re: [PATCH] drm: reduce default drm vblank off delay to 50ms

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Wed, 2 Jul 2014 13:35:19 -0700
Stéphane Marchesin <stephane.marchesin@gmail.com> wrote:

> On Tue, Oct 30, 2012 at 12:20 PM, Daniel Vetter <daniel@ffwll.ch> wrote:
> > On Tue, Oct 30, 2012 at 8:09 PM, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
> >> People keep whining about this, but no one seems to send a patch.  This
> >> *ought* to be safe now that we've dealt with the hw races in Mario's
> >> updated code, and fixed the bugs we know about in VT switch, DPMS, and
> >> multi-head configuraions.
> >>
> >> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> >
> > Afaik the fundamental race of enabling the vblank is still there, so
> > this is just duct-tape. And our hw has the required registers (on
> > gen5+ at least) to close this race for real and abolish all "disable
> > vblank irq later to paper over races and smooth things out). Hence I
> > think we should dtrt and so
> 
> [digging an old thread]
> 
> So I'm looking at this machine where we can't get good PSR residency
> because the vblank_offdelay is so long. Therefore, I'm suddenly very
> interested in solving this issue :) Of course I can't seem to find
> logs of the fun IRC discussion you guys had, can you describe what the
> race is, and also what are the registers you're talking about?

Beyond that I don't see why this obvious and simple improvement should
be blocked on some other work.  Maybe it's a bit late now since Ville
may already have patches for what Daniel mentions above, but I still
find the nack to be totally misguided.

Dave, please just pick this up so everyone can benefit while we thrash
through an i915 fix (doubtless introducing some bugs) that lets us
disable immediately.

-- 
Jesse Barnes, Intel Open Source Technology Center
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