Re: [Intel-gfx] [PATCH v3 5/8] drm/i915/gtt: allow overriding the pt alignment

Ramalingam C
2021-12-13T15:32:41Z

On 2021-12-06 at 13:31:37 +0000, Matthew Auld wrote:
> On some platforms we have alignment restrictions when accessing LMEM
> from the GTT. In the next patch few patches we need to be able to modify
probably extra "patch"

Apart from that looks good to me

Reviewed-by : Ramalingam C <ramalingam.c@intel.com>

> the page-tables directly via the GTT itself.
>
> Suggested-by: Ramalingam C <ramalingam.c@intel.com>
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Cc: Ramalingam C <ramalingam.c@intel.com>
> ---
> drivers/gpu/drm/i915/gt/intel_gtt.h | 10 +++++++++-
> drivers/gpu/drm/i915/gt/intel_ppgtt.c | 16 ++++++++++++----
> 2 files changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h b/drivers/gpu/drm/i915/gt/intel_gtt.h
> index cbc0b5266cb4..a00d278d8175 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gtt.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gtt.h
> @@ -196,6 +196,14 @@ void *__px_vaddr(struct drm_i915_gem_object *p);
> struct i915_vm_pt_stash {
> /* preallocated chains of page tables/directories */
> struct i915_page_table *pt[2];
> + /*
> + * Optionally override the alignment/size of the physical page that
> + * contains each PT. If not set defaults back to the usual
> + * I915_GTT_PAGE_SIZE_4K. This does not influence the other paging
> + * structures. MUST be a power-of-two. ONLY applicable on discrete
> + * platforms.
> + */
> + int pt_sz;
> };
>
> struct i915_vma_ops {
> @@ -583,7 +591,7 @@ void free_scratch(struct i915_address_space *vm);
>
> struct drm_i915_gem_object *alloc_pt_dma(struct i915_address_space *vm, int sz);
> struct drm_i915_gem_object *alloc_pt_lmem(struct i915_address_space *vm, int sz);
> -struct i915_page_table *alloc_pt(struct i915_address_space *vm);
> +struct i915_page_table *alloc_pt(struct i915_address_space *vm, int sz);
> struct i915_page_directory *alloc_pd(struct i915_address_space *vm);
> struct i915_page_directory *__alloc_pd(int npde);
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_ppgtt.c b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> index b8238f5bc8b1..3c90aea25072 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ppgtt.c
> @@ -12,7 +12,7 @@
> #include "gen6_ppgtt.h"
> #include "gen8_ppgtt.h"
>
> -struct i915_page_table *alloc_pt(struct i915_address_space *vm)
> +struct i915_page_table *alloc_pt(struct i915_address_space *vm, int sz)
> {
> struct i915_page_table *pt;
>
> @@ -20,7 +20,7 @@ struct i915_page_table *alloc_pt(struct i915_address_space *vm)
> if (unlikely(!pt))
> return ERR_PTR(-ENOMEM);
>
> - pt->base = vm->alloc_pt_dma(vm, I915_GTT_PAGE_SIZE_4K);
> + pt->base = vm->alloc_pt_dma(vm, sz);
> if (IS_ERR(pt->base)) {
> kfree(pt);
> return ERR_PTR(-ENOMEM);
> @@ -219,17 +219,25 @@ int i915_vm_alloc_pt_stash(struct i915_address_space *vm,
> u64 size)
> {
> unsigned long count;
> - int shift, n;
> + int shift, n, pt_sz;
>
> shift = vm->pd_shift;
> if (!shift)
> return 0;
>
> + pt_sz = stash->pt_sz;
> + if (!pt_sz)
> + pt_sz = I915_GTT_PAGE_SIZE_4K;
> + else
> + GEM_BUG_ON(!IS_DGFX(vm->i915));
> +
> + GEM_BUG_ON(!is_power_of_2(pt_sz));
> +
> count = pd_count(size, shift);
> while (count--) {
> struct i915_page_table *pt;
>
> - pt = alloc_pt(vm);
> + pt = alloc_pt(vm, pt_sz);
> if (IS_ERR(pt)) {
> i915_vm_free_pt_stash(vm, stash);
> return PTR_ERR(pt);
> --
> 2.31.1
>