Re: [igt-dev] [PATCH i-g-t 04/10] lib/igt_draw: Add pixel math for tile-4

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Fri, Feb 25, 2022 at 10:38:47AM +0530, Jeevan B wrote:
> From: Matt Roper <matthew.d.roper@intel.com>
> 
> We need to implement the tile-4 math to convert x,y coordinates to
> buffer offsets and vice versa for cases where we're using the CPU to
> tile/detile rather than a GPU engine (e.g., the mmap_cpu and pwrite
> subtests for kms_draw_crc).
> 
> The bspec description of tiling-4 is very confusing/misleading, but the
> implementation here does match the tile-4 content generated by GPU
> engines and recognized properly by the display controller.
> 
> Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> Signed-off-by: Jeevan B <jeevan.b@intel.com>

Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>

> ---
>  lib/igt_draw.c | 113 ++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 111 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/igt_draw.c b/lib/igt_draw.c
> index 0ca43deb..d78ecdf0 100644
> --- a/lib/igt_draw.c
> +++ b/lib/igt_draw.c
> @@ -226,6 +226,71 @@ static int linear_x_y_to_ytiled_pos(int x, int y, uint32_t stride, int swizzle,
>  	return pos / pixel_size;
>  }
>  
> +#define OW_SIZE 16			/* in bytes */
> +#define TILE_4_SUBTILE_SIZE 64		/* in bytes */
> +#define TILE_4_WIDTH 128		/* in bytes */
> +#define TILE_4_HEIGHT 32		/* in pixels */
> +#define TILE_4_SUBTILE_WIDTH  OW_SIZE	/* in bytes */
> +#define TILE_4_SUBTILE_HEIGHT 4		/* in pixels */
> +
> +/*
> + * Subtile remapping for tile 4.  Note that map[a]==b implies map[b]==a
> + * so we can use the same table to tile and until.
> + */
> +static const int tile4_subtile_map[] = {
> +	0,  1,  2,  3,  8,  9, 10, 11,
> +	4,  5,  6,  7, 12, 13, 14, 15,
> +	16, 17, 18, 19, 24, 25, 26, 27,
> +	20, 21, 22, 23, 28, 29, 30, 31,
> +	32, 33, 34, 35, 40, 41, 42, 43,
> +	36, 37, 38, 39, 44, 45, 46, 47,
> +	48, 49, 50, 51, 56, 57, 58, 59,
> +	52, 53, 54, 55, 60, 61, 62, 63
> +};
> +
> +static int linear_x_y_to_4tiled_pos(int x, int y, uint32_t stride, int swizzle,
> +				    int bpp)
> +{
> +	int tile_base_pos;
> +	int tile_x, tile_y;
> +	int subtile_col, subtile_row, subtile_num, new_subtile_num;
> +	int pixel_size = bpp / 8;
> +	int byte_x = x * pixel_size;
> +	int pos;
> +
> +	/* Modern platforms that have 4-tiling don't use old bit 6 swizzling */
> +	igt_assert_eq(swizzle, I915_BIT_6_SWIZZLE_NONE);
> +
> +	/*
> +	* Where does the 4k tile start (in bytes)?  This is the same for Y and
> +	* F so we can use the Y-tile algorithm to get to that point.
> +	*/
> +	tile_base_pos = (y / TILE_4_HEIGHT) * stride * TILE_4_HEIGHT +
> +		4096 * (byte_x / TILE_4_WIDTH);
> +
> +	/* Find pixel within tile */
> +	tile_x = (byte_x % TILE_4_WIDTH);
> +	tile_y = y % TILE_4_HEIGHT;
> +
> +	/* And figure out the subtile within the 4k tile */
> +	subtile_col = tile_x / TILE_4_SUBTILE_WIDTH;
> +	subtile_row = tile_y / TILE_4_SUBTILE_HEIGHT;
> +	subtile_num = subtile_row * 8 + subtile_col;
> +
> +	/* Swizzle the subtile number according to the bspec diagram */
> +	new_subtile_num = tile4_subtile_map[subtile_num];
> +
> +	/* Calculate new position */
> +	pos = tile_base_pos +
> +		new_subtile_num * TILE_4_SUBTILE_SIZE +
> +		(tile_y % TILE_4_SUBTILE_HEIGHT) * OW_SIZE +
> +		tile_x % TILE_4_SUBTILE_WIDTH;
> +	igt_assert(pos % pixel_size == 0);
> +	pos /= pixel_size;
> +
> +	return pos;
> +}
> +
>  static void xtiled_pos_to_x_y_linear(int tiled_pos, uint32_t stride,
>  				     int swizzle, int bpp, int *x, int *y)
>  {
> @@ -253,6 +318,44 @@ static void ytiled_pos_to_x_y_linear(int tiled_pos, uint32_t stride,
>  	*x /= pixel_size;
>  }
>  
> +static void tile4_pos_to_x_y_linear(int tiled_pos, uint32_t stride,
> +				    int swizzle, int bpp, int *x, int *y)
> +{
> +	int pixel_size = bpp / 8;
> +	int tiles_per_line = stride / TILE_4_WIDTH;
> +	int tile_num, tile_offset, tile_row, tile_col;
> +	int tile_origin_x, tile_origin_y;
> +	int subtile_num, subtile_offset, subtile_row, subtile_col;
> +	int subtile_origin_x, subtile_origin_y;
> +	int oword_num, byte_num;
> +
> +	/* Modern platforms that have 4-tiling don't use old bit 6 swizzling */
> +	igt_assert_eq(swizzle, I915_BIT_6_SWIZZLE_NONE);
> +
> +	/* Calculate the x,y of the start of the 4k tile */
> +	tile_num = tiled_pos / 4096;
> +	tile_row = tile_num / tiles_per_line;
> +	tile_col = tile_num % tiles_per_line;
> +	tile_origin_x = tile_col * TILE_4_WIDTH;
> +	tile_origin_y = tile_row * TILE_4_HEIGHT;
> +
> +	/* Now calculate the x,y offset of the start of the subtile */
> +	tile_offset = tiled_pos % 4096;
> +	subtile_num = tile4_subtile_map[tile_offset / TILE_4_SUBTILE_SIZE];
> +	subtile_row = subtile_num / 8;
> +	subtile_col = subtile_num % 8;
> +	subtile_origin_x = subtile_col * TILE_4_SUBTILE_WIDTH;
> +	subtile_origin_y = subtile_row * TILE_4_SUBTILE_HEIGHT;
> +
> +	/* Next the oword and byte within the subtile */
> +	subtile_offset = tiled_pos % TILE_4_SUBTILE_SIZE;
> +	oword_num = subtile_offset / OW_SIZE;
> +	byte_num = subtile_offset % OW_SIZE;
> +
> +	*x = (tile_origin_x + subtile_origin_x + byte_num) / pixel_size;
> +	*y = tile_origin_y + subtile_origin_y + oword_num;
> +}
> +
>  static void set_pixel(void *_ptr, int index, uint32_t color, int bpp)
>  {
>  	if (bpp == 16) {
> @@ -318,10 +421,13 @@ static void draw_rect_ptr_tiled(void *ptr, uint32_t stride, uint32_t tiling,
>  							       swizzle, bpp);
>  				break;
>  			case I915_TILING_Y:
> -			case I915_TILING_4:
>  				pos = linear_x_y_to_ytiled_pos(x, y, stride,
>  							       swizzle, bpp);
>  				break;
> +			case I915_TILING_4:
> +				pos = linear_x_y_to_4tiled_pos(x, y, stride,
> +							       swizzle, bpp);
> +				break;
>  			default:
>  				igt_assert(false);
>  			}
> @@ -470,10 +576,13 @@ static void draw_rect_pwrite_tiled(int fd, struct buf_data *buf,
>  						 swizzle, buf->bpp, &x, &y);
>  			break;
>  		case I915_TILING_Y:
> -		case I915_TILING_4:
>  			ytiled_pos_to_x_y_linear(tiled_pos, buf->stride,
>  						 swizzle, buf->bpp, &x, &y);
>  			break;
> +		case I915_TILING_4:
> +			tile4_pos_to_x_y_linear(tiled_pos, buf->stride,
> +						swizzle, buf->bpp, &x, &y);
> +			break;
>  		default:
>  			igt_assert(false);
>  		}
> -- 
> 2.17.1
>