Re: [PATCH i-g-t v4 1/5] lib/intel_blt: Add helpers for calculating stride and aligned height

[Karolina Stolarek <karolina.stolarek@intel.com>]

On 1.02.2024 11:07, Zbigniew Kempczyński wrote:
> Tiled surfaces have stride / aligned height constraints. Currently
> blt library has limitation and doesn't work properly when surface
> stride is not valid for specific tiling.
> 
> As an example lets say we want to copy from linear to xmajor
> 33 x 33 x 32bpp surface. Xmajor surface expects stride aligned to
> 512 bytes and height to 8 rows so this surface will occupy 512B x 40
> (128 x 40 x 32 bpp).
> 
> Signed-off-by: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com>
> Cc: Karolina Drobnik <karolina.drobnik@intel.com>

Just a bunch of nits, nothing major.

> ---
> v2: Fix stride/aligned height calculation for Tile64
> v3: Fix stride calculation for xmajor
>      Make helpers public (fixes compilation warning due to lack
>      or static function users)
> ---
>   lib/intel_blt.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++
>   lib/intel_blt.h |  4 ++++
>   2 files changed, 68 insertions(+)
> 
> diff --git a/lib/intel_blt.c b/lib/intel_blt.c
> index 25d251c4f8..13b1dbba4f 100644
> --- a/lib/intel_blt.c
> +++ b/lib/intel_blt.c
> @@ -521,6 +521,70 @@ static int __block_tiling(enum blt_tiling_type tiling)
>   	return 0;
>   }
>   
> +/**
> + * blt_get_min_stride
> + * @width: width in pixels
> + * @bpp: bits per pixel
> + * @tiling: tiling
> + *
> + * Function returns minimum posibble stride in bytes for width, bpp and tiling.

"return" is already described, we could say "calculates minimum possible
stride..."

> + *
> + * Returns:
> + * minimum possible stride in bytes.
> + */
> +uint32_t blt_get_min_stride(uint32_t width, uint32_t bpp,
> +			    enum blt_tiling_type tiling)
> +{
> +	switch (tiling) {
> +	case T_LINEAR:
> +		return width * bpp / 8;
> +	case T_XMAJOR:
> +		return ALIGN(width * bpp / 8, 512);
> +	case T_TILE64:
> +		if (bpp == 8)
> +			return ALIGN(width, 256);
> +		else if (bpp == 16 || bpp == 32)
> +			return ALIGN(width * bpp / 8, 512);
> +		return ALIGN(width * bpp / 8, 1024);
> +
> +	default:
> +		return ALIGN(width * bpp / 8, 128);
> +	}
> +}
> +
> +/**
> + * blt_get_aligned_height
> + * @height: height in pixels
> + * @bpp: bits per pixel (used for Tile64 due to different tile organization
> + * in pixels)
> + * @tiling: tiling
> + *
> + * Function returns aligned height for specific tiling. Height returned is
> + * important from memory allocation perspective, because each tiling has
> + * specific memory constraints.

I'd move the comment on Tile64 to the description body and integrate it
with the last sentence. You could say that each tiling has constrains
dependent on bpp and mention a different pixel order for Tile64 as an
example.

Apart from that, it's looking good to me:

Reviewed-by: Karolina Stolarek <karolina.stolarek@intel.com>

> + *
> + * Returns:
> + * height (rows) expected for specific tiling
> + */
> +uint32_t blt_get_aligned_height(uint32_t height, uint32_t bpp,
> +				enum blt_tiling_type tiling)
> +{
> +	switch (tiling) {
> +	case T_LINEAR:
> +		return height;
> +	case T_XMAJOR:
> +		return ALIGN(height, 8);
> +	case T_TILE64:
> +		if (bpp == 8)
> +			return ALIGN(height, 256);
> +		else if (bpp == 16 || bpp == 32)
> +			return ALIGN(height, 128);
> +		return ALIGN(height, 64);
> +	default:
> +		return ALIGN(height, 32);
> +	}
> +}
> +
>   static int __special_mode(const struct blt_copy_data *blt)
>   {
>   	if (blt->src.handle == blt->dst.handle &&
> diff --git a/lib/intel_blt.h b/lib/intel_blt.h
> index d9be22fdf4..e3084dc0cd 100644
> --- a/lib/intel_blt.h
> +++ b/lib/intel_blt.h
> @@ -212,6 +212,10 @@ bool blt_block_copy_supports_compression(int fd);
>   bool blt_uses_extended_block_copy(int fd);
>   
>   const char *blt_tiling_name(enum blt_tiling_type tiling);
> +uint32_t blt_get_min_stride(uint32_t width, uint32_t bpp,
> +			    enum blt_tiling_type tiling);
> +uint32_t blt_get_aligned_height(uint32_t height, uint32_t bpp,
> +				enum blt_tiling_type tiling);
>   
>   void blt_copy_init(int fd, struct blt_copy_data *blt);
>