Re: [PATCH 03/12] drm/i915: make PDE|PTE platform specific

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Thu, 2 May 2013 15:49:17 -0700
Ben Widawsky <ben@bwidawsk.net> wrote:

> On Thu, May 02, 2013 at 02:26:17PM -0700, Jesse Barnes wrote:
> > On Tue, 23 Apr 2013 23:15:31 -0700
> > Ben Widawsky <ben@bwidawsk.net> wrote:
> > 
> > > Accomplish this be removing the PDE count define which is (and has
> > > always been) part of the PPGTT structure anyway. With the addition of
> > > the gen specific init function, we can nicely tuck away the magic number
> > > in there.
> > > 
> > > In this vain, make the PTE define less of a magic number.
> > 
> > vein
> > 
> > > 
> > > The remaining code in the global gtt setup is a bit messy, but an
> > > upcoming patch will clean that one up.
> > > 
> > > Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> > > ---
> > >  drivers/gpu/drm/i915/i915_drv.h     |  2 --
> > >  drivers/gpu/drm/i915/i915_gem_gtt.c | 10 +++++-----
> > >  2 files changed, 5 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > > index d5dcf7f..0a9c7cd 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.h
> > > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > > @@ -431,8 +431,6 @@ struct i915_gtt {
> > >  };
> > >  #define gtt_total_entries(gtt) ((gtt).total >> PAGE_SHIFT)
> > >  
> > > -#define I915_PPGTT_PD_ENTRIES 512
> > > -#define I915_PPGTT_PT_ENTRIES 1024
> > >  struct i915_hw_ppgtt {
> > >  	struct drm_device *dev;
> > >  	unsigned num_pd_entries;
> > > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > > index 0503f09..11a50cf 100644
> > > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > > @@ -29,6 +29,7 @@
> > >  #include "intel_drv.h"
> > >  
> > >  typedef uint32_t gen6_gtt_pte_t;
> > > +#define I915_PPGTT_PT_ENTRIES (PAGE_SIZE / sizeof(gen6_gtt_pte_t))
> > >  
> > >  /* PPGTT stuff */
> > >  #define GEN6_GTT_ADDR_ENCODE(addr)	((addr) | (((addr) >> 28) & 0xff0))
> > > @@ -235,10 +236,9 @@ static int gen6_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
> > >  	/* 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) - I915_PPGTT_PD_ENTRIES;
> > > +	first_pd_entry_in_global_pt = gtt_total_entries(dev_priv->gtt) - 512;
> > >  
> > > -	ppgtt->num_pd_entries = I915_PPGTT_PD_ENTRIES;
> > > +	ppgtt->num_pd_entries = 512;
> > >  	ppgtt->enable = gen6_ppgtt_enable;
> > >  	ppgtt->clear_range = gen6_ppgtt_clear_range;
> > >  	ppgtt->insert_entries = gen6_ppgtt_insert_entries;
> > > @@ -646,7 +646,7 @@ void i915_gem_init_global_gtt(struct drm_device *dev)
> > >  		if (INTEL_INFO(dev)->gen <= 7) {
> > >  			/* PPGTT pdes are stolen from global gtt ptes, so shrink the
> > >  			 * aperture accordingly when using aliasing ppgtt. */
> > > -			gtt_size -= I915_PPGTT_PD_ENTRIES*PAGE_SIZE;
> > > +			gtt_size -= 512 * PAGE_SIZE;
> > >  		}
> > >  
> > >  		i915_gem_setup_global_gtt(dev, 0, mappable_size, gtt_size);
> > > @@ -657,7 +657,7 @@ void i915_gem_init_global_gtt(struct drm_device *dev)
> > >  
> > >  		DRM_ERROR("Aliased PPGTT setup failed %d\n", ret);
> > >  		drm_mm_takedown(&dev_priv->mm.gtt_space);
> > > -		gtt_size += I915_PPGTT_PD_ENTRIES*PAGE_SIZE;
> > > +		gtt_size += 512 * PAGE_SIZE;
> > >  	}
> > >  	i915_gem_setup_global_gtt(dev, 0, mappable_size, gtt_size);
> > >  }
> > 
> > I thought we could have 1024 PDEs?  Either way, this just drops the
> > macro, which is fine, unless we want to increase our PDE count.
> > 
> > Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> 
> Thanks for the review.
> 
> I think the docs must be wrong if they say this. 512PDEs are all you
> need to map a 2GB address space (which is the max), and furthermore, the
> DCLV which is used to indicate the size of the PDEs can only allow up to 2GB.

Agreed, one of the diagrams indicates a 4k set of PDEs, but the DCLV
reg says 32 * 16 entries.  So the 512 is fine.

-- 
Jesse Barnes, Intel Open Source Technology Center