[Intel-gfx] [PATCH] drm/agp: agp-intel/i915: trim stolen space to 16M

[Jesse Barnes]

On Thu, 25 Mar 2010 11:18:38 +0800
Zhenyu Wang <zhenyuw at linux.intel.com> wrote:

> On 2010.03.24 13:28:18 -0700, Jesse Barnes wrote:
> > On Wed, 24 Mar 2010 13:06:05 -0700
> > Eric Anholt <eric at anholt.net> wrote:
> > 
> > > On Mon, 22 Mar 2010 11:17:46 -0700, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> > > > On my SDV, the BIOS allocates 128M of stolen space no matter what
> > > > settings I use.  This leaves very little aperture space available (at
> > > > least relatively so given my 30" + 24" desktop setup) for mapping
> > > > buffers in execbuf.
> > > > 
> > > > I've been using this patch for awhile to work around the problem, and
> > > > think it's a reasonable thing to apply.  We generally only need a small
> > > > amount of stolen space for the few things that need contiguous space,
> > > > the compressed frame buffer being the biggest.
> > > > 
> > > > I think I have an idea of how to reclaim the space and give it back to
> > > > linux, but I haven't tested that yet; I'll post a follow-up patch on
> > > > top of this one when I have it working (basically changing the memory
> > > > back to WB using MTRR and/or set_memory_* calls and using memory
> > > > hotplug's add_memory() call to return it to the system).
> > > > 
> > > > Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
> > > 
> > > I love the idea!  The interactions between the two modules are sure
> > > ugly, though -- like the duplication of i915_probe_agp().  That's part
> > > of why I've wished we would just pull GTT setup into the DRM and leave
> > > intel-agp to rot for non-KMS support that actually uses the agpgart
> > > interfaces.
> > 
> > Agreed.  I briefly looked at cleaning that up too, but it seemed pretty
> > invasive to the AGP and DRM code, so I left it for another day.
> 
> yeah, another benefit I can think of is that if we want to do PPGTT support
> in future, we don't have to hook up possible new APIs in AGP to serve DRM,
> which is really inconvenient.

Note the stolen adjustment doesn't seem to be necessary on production
level machines.  I blame my pre-production BIOS for the bogus size.  I
think Daniel should still proceed with his cleanups, but we don't need
to worry about reclaiming space as much, at least not for now.

-- 
Jesse Barnes, Intel Open Source Technology Center