Re: [PATCH 2/2] drm/i915: Document the multi-threaded FORCEWAKE bits

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Wed, 17 Oct 2012 09:27:24 -0700
Jesse Barnes <jbarnes@virtuousgeek.org> wrote:

> On Wed, 17 Oct 2012 12:09:55 +0100
> Chris Wilson <chris@chris-wilson.co.uk> wrote:
> 
> > No functional change, but reserves 0x2 for use by userspace.
> > 
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/i915_reg.h |    2 ++
> >  drivers/gpu/drm/i915/intel_pm.c |   10 +++++-----
> >  2 files changed, 7 insertions(+), 5 deletions(-)
> 
> Each of the bits in this reg correspond to a specific agent that may
> need to wake the GT.  Unfortunately I don't have docs about which bits
> are used by which agents.  IIRC the BIOS uses one as does the AMT
> engine if present.
> 
> I'll try to find out who owns each and maybe we can reserve our own for
> userspace.

Ok we're in the clear here.  I was afraid there might be other system
components that would do sneaky things behind our back.  But once the
driver loads, we own the GT, so we can make these bits whatever we want.

-- 
Jesse Barnes, Intel Open Source Technology Center