Re: [PATCH 2/2] drm/i915: Assert we hold the CRTC powerwell for generating vblank interrupts

Chris Wilson
2016-10-10T09:58:18Z

On Mon, Oct 10, 2016 at 11:35:07AM +0200, Maarten Lankhorst wrote:
> Op 07-10-16 om 21:49 schreef Chris Wilson:
> > To enable the vblank itself, we need to have an RPM wakeref for the mmio
> > access, and whilst generating the vblank interrupts we continue to
> > require the rpm wakeref. The assumption is that the RPM wakeref is held
> > by the display powerwell held by the active pipe. As this chain was not
> > obvious to me chasing the drm_wait_vblank ioctl, document it with a WARN
> > during *_vblank_enable().
> >
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Don't we prevent enabling the vblank irq through drm_crtc_vblank_on/off?

Should, but this is the boundary point from the midlayer, so
sanitychecks ahoy.

> I'd rather not have things look at crtc->state if possible, locking might not help you.

Ok, anything better?
-Chris

--
Chris Wilson, Intel Open Source Technology Centre