Re: [PATCH 22/48] drm/i915: Use drm_mm for PPGTT PDEs

Chris Wilson
2014-03-24T19:46:01Z

On Mon, Mar 24, 2014 at 12:36:23PM -0700, Ben Widawsky wrote:
> On Thu, Mar 20, 2014 at 11:10:13AM +0000, Chris Wilson wrote:
> > On Fri, Dec 06, 2013 at 02:11:55PM -0800, Ben Widawsky wrote:
> > > static int gen6_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
> > > {
> > > +#define GEN6_PD_ALIGN (PAGE_SIZE * 16)
> > > +#define GEN6_PD_SIZE (GEN6_PPGTT_PD_ENTRIES * PAGE_SIZE)
> > > struct drm_device *dev = ppgtt->base.dev;
> > > struct drm_i915_private *dev_priv = dev->dev_private;
> > > - unsigned first_pd_entry_in_global_pt;
> > > - int i;
> > > - int ret = -ENOMEM;
> > > + int i, ret;
> > >
> > > - /* ppgtt PDEs reside in the global gtt pagetable, which has 512*1024
> > > - * entries. For aliasing ppgtt support we just steal them at the end for
> > > - * now. */
> > > - first_pd_entry_in_global_pt = gtt_total_entries(dev_priv->gtt);
> > > + /* PPGTT PDEs reside in the GGTT and consists of 512 entries. The
> > > + * allocator works in address space sizes, so it's multiplied by page
> > > + * size. We allocate at the top of the GTT to avoid fragmentation.
> > > + */
> > > + BUG_ON(!drm_mm_initialized(&dev_priv->gtt.base.mm));
> > > + ret = drm_mm_insert_node_in_range_generic(&dev_priv->gtt.base.mm,
> > > + &ppgtt->node, GEN6_PD_SIZE,
> > > + GEN6_PD_ALIGN, 0,
> > > + 0, dev_priv->gtt.base.total,
> > > + DRM_MM_SEARCH_DEFAULT);
> > This could use the simpler drm_mm_insert_node_generic().
> > -Chris
> >
>
> Not with my [simple] workaround to not use offset 0, which Daniel
> reverted. I think he has some hope that we'll actually be able to figure
> out why we can't use offset 0 instead of just using the workaround.

You can simply reduce the drm_mm range...
-Chris

--
Chris Wilson, Intel Open Source Technology Centre