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

[Daniel Vetter]

On Wed, Jul 02, 2014 at 01:42:38PM -0700, Jesse Barnes wrote:
> On Wed, 2 Jul 2014 13:35:19 -0700
> Stéphane Marchesin <stephane.marchesin at gmail.com> wrote:
> 
> > On Tue, Oct 30, 2012 at 12:20 PM, Daniel Vetter <daniel at ffwll.ch> wrote:
> > > On Tue, Oct 30, 2012 at 8:09 PM, Jesse Barnes <jbarnes at 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 at 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.

This needs an ack from Mario.

And I really don't see why we _now_ need to suddenly rush then when we
have patches from Ville to address this properly. The blocker is only that
it's not yet reviewed but meh.

And people with product ship dates looming over their head can always just
apply this themselves.

Us sucking at reviewing is imo no reason at all to rush patches in.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch