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

[Daniel Vetter <daniel@ffwll.ch>]

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>

I've written this code, so I know what the magic 512 is all about. But
since Jesse is already confused about them I don't like removing the
#define that much. Heck, we even tend to use PAGE_SIZE instead of 4096.

What about a GEN6_ prefix instead? Or if you want to make this dynamic
(iirc we can allocated PDEs in groups of 32) call it _MAX or so?

I like the PT entries part though.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch