Re: [PATCH v6 04/19] drm/i915/gen8: Generalize PTE writing for GEN8 PPGTT

["Goel, Akash" <akash.goel@intel.com>]

On 7/29/2015 9:53 PM, Michel Thierry wrote:
> The insert_entries function was the function used to write PTEs. For the
> PPGTT it was "hardcoded" to only understand two level page tables, which
> was the case for GEN7. We can reuse this for 4 level page tables, and
> remove the concept of insert_entries, which was never viable past 2
> level page tables anyway, but it requires a bit of rework to make the
> function a bit more generic.
>
> This patch begins the generalization work, and it will be heavily used
> upon when the 48b code is complete. The patch series attempts to make
> each function which touches a part of code specific to the page table
> level and here is no exception.
>
> v2: Rebase after Mika's ppgtt cleanup / scratch merge patch series.
> v3: Rebase after final merged version of Mika's ppgtt/scratch patches.
>
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> Signed-off-by: Michel Thierry <michel.thierry@intel.com> (v2)
> ---
>   drivers/gpu/drm/i915/i915_gem_gtt.c | 52 +++++++++++++++++++++++++++----------
>   1 file changed, 39 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index bd56979..f338a13 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -600,24 +600,21 @@ static int gen8_mm_switch(struct i915_hw_ppgtt *ppgtt,
>   	return 0;
>   }
>
> -static void gen8_ppgtt_clear_range(struct i915_address_space *vm,
> -				   uint64_t start,
> -				   uint64_t length,
> -				   bool use_scratch)
> +static void gen8_ppgtt_clear_pte_range(struct i915_address_space *vm,
> +				       struct i915_page_directory_pointer *pdp,
> +				       uint64_t start,
> +				       uint64_t length,
> +				       gen8_pte_t scratch_pte)
>   {
>   	struct i915_hw_ppgtt *ppgtt =
>   		container_of(vm, struct i915_hw_ppgtt, base);
> -	struct i915_page_directory_pointer *pdp = &ppgtt->pdp; /* FIXME: 48b */
> -	gen8_pte_t *pt_vaddr, scratch_pte;
> +	gen8_pte_t *pt_vaddr;
>   	unsigned pdpe = start >> GEN8_PDPE_SHIFT & GEN8_PDPE_MASK;
>   	unsigned pde = start >> GEN8_PDE_SHIFT & GEN8_PDE_MASK;
>   	unsigned pte = start >> GEN8_PTE_SHIFT & GEN8_PTE_MASK;
>   	unsigned num_entries = length >> PAGE_SHIFT;
>   	unsigned last_pte, i;
>
> -	scratch_pte = gen8_pte_encode(px_dma(ppgtt->base.scratch_page),
> -				      I915_CACHE_LLC, use_scratch);
> -

Sorry for the late comment.
Would it be better to have a WARN_ON check here on NULL value of pdp 
pointer, considering the pdp will no longer be static in case of 48 bit.

Actually there are already such checks used in this function for pd, pt 
and page pointers.

Best regards
Akash

>   	while (num_entries) {
>   		struct i915_page_directory *pd;
>   		struct i915_page_table *pt;
> @@ -656,14 +653,30 @@ static void gen8_ppgtt_clear_range(struct i915_address_space *vm,
>   	}
>   }
>
> -static void gen8_ppgtt_insert_entries(struct i915_address_space *vm,
> -				      struct sg_table *pages,
> -				      uint64_t start,
> -				      enum i915_cache_level cache_level, u32 unused)
> +static void gen8_ppgtt_clear_range(struct i915_address_space *vm,
> +				   uint64_t start,
> +				   uint64_t length,
> +				   bool use_scratch)
>   {
>   	struct i915_hw_ppgtt *ppgtt =
>   		container_of(vm, struct i915_hw_ppgtt, base);
>   	struct i915_page_directory_pointer *pdp = &ppgtt->pdp; /* FIXME: 48b */
> +
> +	gen8_pte_t scratch_pte = gen8_pte_encode(px_dma(vm->scratch_page),
> +						 I915_CACHE_LLC, use_scratch);
> +
> +	gen8_ppgtt_clear_pte_range(vm, pdp, start, length, scratch_pte);
> +}
> +
> +static void
> +gen8_ppgtt_insert_pte_entries(struct i915_address_space *vm,
> +			      struct i915_page_directory_pointer *pdp,
> +			      struct sg_table *pages,
> +			      uint64_t start,
> +			      enum i915_cache_level cache_level)
> +{
> +	struct i915_hw_ppgtt *ppgtt =
> +		container_of(vm, struct i915_hw_ppgtt, base);
>   	gen8_pte_t *pt_vaddr;
>   	unsigned pdpe = start >> GEN8_PDPE_SHIFT & GEN8_PDPE_MASK;
>   	unsigned pde = start >> GEN8_PDE_SHIFT & GEN8_PDE_MASK;
> @@ -700,6 +713,19 @@ static void gen8_ppgtt_insert_entries(struct i915_address_space *vm,
>   		kunmap_px(ppgtt, pt_vaddr);
>   }
>
> +static void gen8_ppgtt_insert_entries(struct i915_address_space *vm,
> +				      struct sg_table *pages,
> +				      uint64_t start,
> +				      enum i915_cache_level cache_level,
> +				      u32 unused)
> +{
> +	struct i915_hw_ppgtt *ppgtt =
> +		container_of(vm, struct i915_hw_ppgtt, base);
> +	struct i915_page_directory_pointer *pdp = &ppgtt->pdp; /* FIXME: 48b */
> +
> +	gen8_ppgtt_insert_pte_entries(vm, pdp, pages, start, cache_level);
> +}
> +
>   static void gen8_free_page_tables(struct drm_device *dev,
>   				  struct i915_page_directory *pd)
>   {
>
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