[Intel-gfx] [PATCH 05/11] drm/i915/gtt: Compute the radix for gen8 page table levels

[Chris Wilson]

Quoting Chris Wilson (2019-07-07 22:00:18)
> The radix levels of each page directory are easily determined so replace
> the numerous hardcoded constants with precomputed derived constants.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_gem_gtt.c | 39 +++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 2fc60e8acd9a..271305705c1c 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -868,6 +868,45 @@ static int gen8_ppgtt_notify_vgt(struct i915_ppgtt *ppgtt, bool create)
>         return 0;
>  }
>  
> +/* Index shifts into the pagetable are offset by GEN8_PTE_SHIFT [12] */
> +#define gen8_pd_shift(lvl) ((lvl) * ilog2(I915_PDES))
> +#define gen8_pd_index(i, lvl) i915_pde_index((i), gen8_pd_shift(lvl))
> +#define __gen8_pte_shift(lvl) (GEN8_PTE_SHIFT + gen8_pd_shift(lvl))
> +#define __gen8_pte_index(a, lvl) i915_pde_index((a), __gen8_pte_shift(lvl))
> +
> +static inline unsigned int
> +gen8_pd_range(u64 addr, u64 end, int lvl, unsigned int *idx)
> +{
> +       const int shift = gen8_pd_shift(lvl);
> +       const u64 mask = ~0ull << gen8_pd_shift(lvl + 1);
> +
> +       GEM_BUG_ON(addr >= end);
> +       end += ~mask >> gen8_pd_shift(1);
> +
> +       *idx = i915_pde_index(addr, shift);
> +       if ((addr ^ end) & mask)
> +               return I915_PDES - *idx;
> +       else
> +               return i915_pde_index(end, shift) - *idx;
> +}
> +
> +static inline bool gen8_pd_subsumes(u64 addr, u64 end, int lvl)
> +{
> +       const u64 mask = ~0ull << gen8_pd_shift(lvl + 1);
> +
> +       GEM_BUG_ON(addr >= end);
> +       return (addr ^ end) & mask && (addr & ~mask) == 0;
> +}
> +
> +static inline unsigned int gen8_pt_count(u64 addr, u64 end)
> +{
> +       GEM_BUG_ON(addr >= end);
> +       if ((addr ^ end) & ~I915_PDE_MASK)
> +               return I915_PDES - (addr & I915_PDE_MASK);
> +       else
> +               return end - addr;
> +}

So this is the question, do you want these as 512 and 0x1ff?

Or just define gen8_pd_shift(lvl) as ((lvl) * ilog(512))

and work from there. Hmm.
-Chris