Re: [PATCH 06/10] drm/i915: Enable vblank_disable_immediate on gen2

Chris Wilson
2015-12-16T10:41:07Z

On Wed, Dec 16, 2015 at 11:31:31AM +0100, Daniel Vetter wrote:
> On Mon, Dec 14, 2015 at 06:23:45PM +0200, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > Since
> > commit 4dfd648 ("drm: Use vblank timestamps to guesstimate how many vblanks were missed")
> > the vblank code can cook up a frame counter value based on
> > the vblank timestamps (as long as they're accurate), so there's
> > no longer any need to keep vblank interrupts enabled on gen2
> > when no one is interested in them. So let's opt into the
> > immediate disable scheme on gen2 as well.
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Yeah makes sense. Userspace that cares can simply ask for a vblank event
> in 1000 frames or so, to keep the vblank interrupt enabled.

I prefer my don't do immediate_disable until after we finish the vblank
event.

I have vblank/flip keepalives in userspace - but at the end of the day
they just add work when we can make a change in the kernel to reduce work.
-Chris

--
Chris Wilson, Intel Open Source Technology Centre