Re: [PATCH 07/10] drm/i915: Calculate correct stolen size for GEN7+

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Thu, 25 Oct 2012 15:15:25 -0700
Ben Widawsky <ben@bwidawsk.net> wrote:

> On Thu, 25 Oct 2012 14:06:48 -0700
> Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
> 
> > On Mon, 22 Oct 2012 18:34:12 -0700
> > Ben Widawsky <ben@bwidawsk.net> wrote:
> > 
> > > This bug existed in the old code, but was easier to fix here in the
> > > rework. Unfortunately gen7 doesn't have a nice way to figure out the
> > > size and we must use a lookup table.
> > > 
> > > Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> > > ---
> > >  drivers/gpu/drm/i915/i915_gem_gtt.c | 14 +++++++++++++-
> > >  drivers/gpu/drm/i915/i915_reg.h     |  2 ++
> > >  2 files changed, 15 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > > index 7d3ec42..16fe960 100644
> > > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > > @@ -528,6 +528,15 @@ static inline unsigned int gen6_get_stolen_size(u16 snb_gmch_ctl)
> > >  	return snb_gmch_ctl << 25; /* 32 MB units */
> > >  }
> > >  
> > > +static inline unsigned int gen7_get_stolen_size(u16 snb_gmch_ctl)
> > > +{
> > > +	static const int stolen_decoder[] = {
> > > +		0, 0, 0, 0, 0, 32, 48, 64, 128, 256, 96, 160, 224, 352};
> > > +	snb_gmch_ctl >>= IVB_GMCH_GMS_SHIFT;
> > > +	snb_gmch_ctl &= IVB_GMCH_GMS_MASK;
> > > +	return stolen_decoder[snb_gmch_ctl] << 20;
> > > +}
> > > +
> > >  int i915_gem_gtt_init(struct drm_device *dev)
> > >  {
> > >  	struct drm_i915_private *dev_priv = dev->dev_private;
> > > @@ -575,7 +584,10 @@ int i915_gem_gtt_init(struct drm_device *dev)
> > >  	pci_read_config_word(dev->pdev, SNB_GMCH_CTRL, &snb_gmch_ctl);
> > >  	dev_priv->mm.gtt->gtt_total_entries =
> > >  		gen6_get_total_gtt_size(snb_gmch_ctl) / sizeof(gtt_pte_t);
> > > -	dev_priv->mm.gtt->stolen_size = gen6_get_stolen_size(snb_gmch_ctl);
> > > +	if (INTEL_INFO(dev)->gen < 7)
> > > +		dev_priv->mm.gtt->stolen_size = gen6_get_stolen_size(snb_gmch_ctl);
> > > +	else
> > > +		dev_priv->mm.gtt->stolen_size = gen7_get_stolen_size(snb_gmch_ctl);
> > >  
> > >  	ret = setup_scratch_page(dev);
> > >  	if (ret)
> > > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > > index 10a6e9b..1d54328 100644
> > > --- a/drivers/gpu/drm/i915/i915_reg.h
> > > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > > @@ -45,6 +45,8 @@
> > >  #define    SNB_GMCH_GGMS_MASK	0x3
> > >  #define    SNB_GMCH_GMS_SHIFT   3 /* Graphics Mode Select */
> > >  #define    SNB_GMCH_GMS_MASK    0x1f
> > > +#define    IVB_GMCH_GMS_SHIFT   4
> > > +#define    IVB_GMCH_GMS_MASK    0xf
> > >  
> > >  
> > >  /* PCI config space */
> > 
> > Hm my docs say different.  Supposedly the size field starts at bit 3
> > and is 5 bits wide, going up to 512M.  So just like SNB but with a
> > bigger max.
> > 
> 
> So we discussed this a bit on IRC. I think we decided to leave it as is?

Yeah, the docs don't agree, but we'll use the graphics ones and hope
for the best.

-- 
Jesse Barnes, Intel Open Source Technology Center