Re: [PATCH 01/11] drm/i915: Move gtt and ppgtt under address space umbrella

[Ben Widawsky <ben@bwidawsk.net>]

On Thu, Jul 11, 2013 at 02:14:06PM +0300, Imre Deak wrote:
> On Mon, 2013-07-08 at 23:08 -0700, Ben Widawsky wrote:
> > The GTT and PPGTT can be thought of more generally as GPU address
> > spaces. Many of their actions (insert entries), state (LRU lists) and
> > many of their characteristics (size), can be shared. Do that.
> > 
> > The change itself doesn't actually impact most of the VMA/VM rework
> > coming up, it just fits in with the grand scheme. GGTT will usually be a
> > special case where we either know an object must be in the GGTT (dislay
> > engine, workarounds, etc.).
> > 
> > v2: Drop usage of i915_gtt_vm (Daniel)
> > Make cleanup also part of the parent class (Ben)
> > Modified commit msg
> > Rebased
> > 
> > Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> > ---
> >  drivers/gpu/drm/i915/i915_debugfs.c |   4 +-
> >  drivers/gpu/drm/i915/i915_dma.c     |   4 +-
> >  drivers/gpu/drm/i915/i915_drv.h     |  57 ++++++-------
> >  drivers/gpu/drm/i915/i915_gem.c     |   4 +-
> >  drivers/gpu/drm/i915/i915_gem_gtt.c | 162 ++++++++++++++++++++----------------
> >  5 files changed, 121 insertions(+), 110 deletions(-)
> > 
> >[...]
> > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > index 242d0f9..693115a 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > @@ -102,7 +102,7 @@ static gen6_gtt_pte_t hsw_pte_encode(dma_addr_t addr,
> >  
> >  static void gen6_write_pdes(struct i915_hw_ppgtt *ppgtt)
> >  {
> > -	struct drm_i915_private *dev_priv = ppgtt->dev->dev_private;
> > +	struct drm_i915_private *dev_priv = ppgtt->base.dev->dev_private;
> >  	gen6_gtt_pte_t __iomem *pd_addr;
> >  	uint32_t pd_entry;
> >  	int i;
> > @@ -181,18 +181,18 @@ static int gen6_ppgtt_enable(struct drm_device *dev)
> >  }
> >  
> >  /* PPGTT support for Sandybdrige/Gen6 and later */
> > -static void gen6_ppgtt_clear_range(struct i915_hw_ppgtt *ppgtt,
> > +static void gen6_ppgtt_clear_range(struct i915_address_space *vm,
> >  				   unsigned first_entry,
> >  				   unsigned num_entries)
> >  {
> > -	struct drm_i915_private *dev_priv = ppgtt->dev->dev_private;
> > +	struct i915_hw_ppgtt *ppgtt =
> > +		container_of(vm, struct i915_hw_ppgtt, base);
> >  	gen6_gtt_pte_t *pt_vaddr, scratch_pte;
> >  	unsigned act_pt = first_entry / I915_PPGTT_PT_ENTRIES;
> >  	unsigned first_pte = first_entry % I915_PPGTT_PT_ENTRIES;
> >  	unsigned last_pte, i;
> >  
> > -	scratch_pte = ppgtt->pte_encode(dev_priv->gtt.scratch.addr,
> > -					I915_CACHE_LLC);
> > +	scratch_pte = vm->pte_encode(vm->scratch.addr, I915_CACHE_LLC);
> 
> I only see ggtt's scratch page being initialized, but can't find the
> corresponding init/teardown for ppgtt. Btw, why do we need separate
> global/per-process scratch pages? (would be nice to add it to the commit
> message)
> 
> --Imre
> 

There is indeed a bug here, it existed somewhere, so I've mistakenly dropped
it. Here is my local fix, which is what I had done previously.

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 552e4cb..c8130db 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -295,6 +295,7 @@ static int gen6_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
        ppgtt->base.clear_range = gen6_ppgtt_clear_range;
        ppgtt->base.bind_object = gen6_ppgtt_bind_object;
        ppgtt->base.cleanup = gen6_ppgtt_cleanup;
+       ppgtt->base.scratch = dev_priv->gtt.base.scratch;
        ppgtt->pt_pages = kzalloc(sizeof(struct page *)*ppgtt->num_pd_entries,
                                  GFP_KERNEL);
        if (!ppgtt->pt_pages)


Not sure what you mean, there should be only 1 scratch page now.

-- 
Ben Widawsky, Intel Open Source Technology Center