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

[Ben Widawsky <ben@bwidawsk.net>]

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.


-- 
Ben Widawsky, Intel Open Source Technology Center