[Intel-gfx] [PATCH] drm/i915: deferring the HSW IPS enable at plane switch

[Daniel Vetter]

On Sun, Jan 19, 2014 at 1:47 PM, Ramalingam C <ramalingam.c at intel.com> wrote:
> To remove the wait_for_vblank from the plane switch execution path,
> this change implements a function which will add a delayed work to
> defer the IPS enable.
>
> The delay is nothing but frame length, which is calculated based on
> vrefresh of the hwmode. i.e IPS enable will be scheduled after a frame.
> If mode is not set during the plane switch (__unlikely__), delay will
> fallback to a default value 100mSec (can handle the FPS >= 10).
>
> Signed-off-by: Ramalingam C <ramalingam.c at intel.com>

We have a general need to do abitrary stuff in both irq and process
context on future vblanks. Chris started with such infrastructure
already:

http://lists.freedesktop.org/archives/intel-gfx/2012-April/016557.html

We've had a fair bit of discussion about where to go to with all this,
but atm this is stalled. I also think we should have this bit of
infrastructure generally available for drivers in drm_vblank.c.

The other thing to keep in mind is to make this fit with Ville's plan
for nuclear pageflips. I think in the end the modeset code should only
fire up the pipe itself (i.e. we'll display a nice black) and enabling
pipes, sprites and cursors should happen with the nuclear pageflip
code. Otherwise we need to duplicate this logic, which usually means
twice the bugs.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch