[Mesa-dev] [PATCH 5/5] i965/gen9: Allocate YF/YS tiled buffer objects

[Ben Widawsky]

On Wed, Jun 10, 2015 at 03:30:50PM -0700, Anuj Phogat wrote:
> In case of I915_TILING_{X,Y} we need to pass tiling format to libdrm
> using drm_intel_bo_alloc_tiled(). But, In case of YF/YS tiled buffers
> libdrm need not know about the tiling format because these buffers
> don't have hardware support to be tiled or detiled through a fenced
> region. libdrm still need to know buffer alignment value for its use
> in kernel when resolving the relocation.
> 
> Using drm_intel_bo_alloc_for_render() for YF/YS tiled buffers
> satisfy both the above conditions.
> 
> Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
> Cc: Ben Widawsky <ben at bwidawsk.net>
> ---
>  src/mesa/drivers/dri/i965/intel_mipmap_tree.c | 86 +++++++++++++++++++++++++--
>  1 file changed, 80 insertions(+), 6 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> index 615cbfb..d4d9e76 100644
> --- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> +++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> @@ -522,6 +522,65 @@ intel_lower_compressed_format(struct brw_context *brw, mesa_format format)
>     }
>  }
>  
> +/* This function computes Yf/Ys tiled bo size and alignment. */

It also computes pitch for the yf/ys case

> +static uint64_t
> +intel_get_yf_ys_bo_size(struct intel_mipmap_tree *mt, unsigned *alignment)
> +{
> +   const uint32_t bpp = mt->cpp * 8;
> +   const uint32_t aspect_ratio = (bpp == 16 || bpp == 64) ? 2 : 1;
> +   uint32_t tile_width, tile_height;
> +   const uint64_t min_size = 512 * 1024;
> +   const uint64_t max_size = 64 * 1024 * 1024;

Where do min/max come from? Add a comment?

> +   uint64_t i, stride, size, aligned_y;
> +
> +   assert(mt->tr_mode != INTEL_MIPTREE_TRMODE_NONE);
> +
> +   switch (bpp) {
> +   case 8:
> +      tile_height = 64;
> +      break;
> +   case 16:
> +   case 32:
> +      tile_height = 32;
> +      break;
> +   case 64:
> +   case 128:
> +      tile_height = 16;
> +      break;
> +   default:
> +      tile_height = 0;

make this unreachable()

> +      printf("Invalid bits per pixel in %s: bpp = %d\n",
> +             __FUNCTION__, bpp);
> +   }

I think ideally you should roll this logic into intel_miptree_get_tile_masks().

> +
> +   if (mt->tr_mode == INTEL_MIPTREE_TRMODE_YS)
> +      tile_height *= 4;
> +
> +   aligned_y = ALIGN(mt->total_height, tile_height);
> +
> +   stride = mt->total_width * mt->cpp;
> +   tile_width = tile_height * mt->cpp * aspect_ratio;
> +   stride = ALIGN(stride, tile_width);
> +   size = stride * aligned_y;
> +
> +   if (mt->tr_mode == INTEL_MIPTREE_TRMODE_YF) {
> +      *alignment = 4096;
> +      size = ALIGN(size, 4096);
> +   } else {
> +      *alignment = 64 * 1024;
> +      size = ALIGN(size, 64 * 1024);
> +   }

Hmm. I think the above calculation for size is redundant since you already
aligned to tile_width and height, above. Right? assert((size % 64K) == 0);

> +
> +   if (size > max_size) {
> +      mt->tr_mode = INTEL_MIPTREE_TRMODE_NONE;
> +      return 0;
> +   } else {
> +      mt->pitch = stride;
> +      for (i = min_size; i < size; i <<= 1)
> +         ;
> +      return i;

I don't understand this. Why don't you just return size? It seems incredibly
wasteful to both start a 512K, and to increment by powers of 2. Did I miss
something?

Also, I don't understand max_size. I must be missing something in the spec with
the min/max values, can you point me to them?

> +   }
> +}
>  
>  struct intel_mipmap_tree *
>  intel_miptree_create(struct brw_context *brw,
> @@ -575,12 +634,27 @@ intel_miptree_create(struct brw_context *brw,
>  
>     unsigned long pitch;
>     mt->etc_format = etc_format;
> -   mt->bo = drm_intel_bo_alloc_tiled(brw->bufmgr, "miptree",
> -                                     total_width, total_height, mt->cpp,
> -                                     &mt->tiling, &pitch,
> -                                     (expect_accelerated_upload ?
> -                                      BO_ALLOC_FOR_RENDER : 0));
> -   mt->pitch = pitch;
> +
> +   if (mt->tr_mode != INTEL_MIPTREE_TRMODE_NONE) {
> +      unsigned alignment = 0;
> +      unsigned long size;
> +      size = intel_get_yf_ys_bo_size(mt, &alignment);
> +
> +      /* intel_get_yf_ys_bo_size() might change the tr_mode. */
> +      if (size > 0 && mt->tr_mode != INTEL_MIPTREE_TRMODE_NONE) {
> +         mt->bo = drm_intel_bo_alloc_for_render(brw->bufmgr, "miptree",
> +                                                size, alignment);
> +      }
> +   }
> +
> +   if (mt->tr_mode == INTEL_MIPTREE_TRMODE_NONE) {
> +      mt->bo = drm_intel_bo_alloc_tiled(brw->bufmgr, "miptree",
> +                                        total_width, total_height, mt->cpp,
> +                                        &mt->tiling, &pitch,
> +                                        (expect_accelerated_upload ?
> +                                         BO_ALLOC_FOR_RENDER : 0));
> +      mt->pitch = pitch;
> +   }
>  
>     /* If the BO is too large to fit in the aperture, we need to use the
>      * BLT engine to support it.  Prior to Sandybridge, the BLT paths can't

Assuming we can sort out the min/max stuff, and power of 2 size, the rest looks
good.