ail: Handle multisampling

It appears that multisampled textures on AGX have all samples of the same pixel
contiguous in memory, effectively using the layout of a single-sampled texture
with a larger block size. Handle in ail.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19871>

src/asahi/layout/README

@@ -5,5 +5,26 @@ encountered with AGX hardware. Its design is inspired by isl. In
 particular, ail strives to use isl unit suffixes and to represent
 quantities in a canonical, API-agnostic fashion.
 
-See the isl documentation for conventions in mesa/docs/isl for the conventions
-that ail tries to adhere to, in particular mesa/docs/isl/units.rst.
+ail conventions differ slightly from isl. See the isl documentation in
+mesa/docs/isl for the conventions that inspired ail, in particular
+mesa/docs/isl/units.rst.
+
+In ail, we have the following units:
+
+**Bytes (B)**: 8-bits.
+
+**Samples (sa)**: An individual sample. The number of bytes per sample depends
+on the format.
+
+**Pixels (px)**: The unit everything starts as from the API. A pixel contains a
+fixed number of samples, given as the layout's `sample_count_sa`. For twiddled
+layouts, these samples are stored together in emmory.
+
+**Elements (el)**: For a block-compressed format, a single compression block
+containing multiple pixels. Otherwise, equal to a single pixel.
+
+**Tiles (tiles)**: Defined only for tiled/twiddled layouts. A group of elements
+forming the layout-specific tile.
+
+We do not support any multisampled block-compressed layouts, so either pixels
+equals either samples or elements.

src/asahi/layout/layout.c

@@ -73,12 +73,28 @@ ail_get_max_tile_size(unsigned blocksize_B)
    }
 }
 
+/*
+ * Calculate the number of bytes in a block. This must take both block
+ * dimensions and multisampling into account.
+ */
+static uint32_t
+ail_get_block_size_B(struct ail_layout *layout)
+{
+   ASSERTED const struct util_format_description *desc =
+      util_format_description(layout->format);
+
+   assert(((layout->sample_count_sa == 1) ||
+           (desc->block.width == 1 && desc->block.height == 1)) &&
+          "multisampling and block-compression are mutually-exclusive");
+
+   return util_format_get_blocksize(layout->format) * layout->sample_count_sa;
+}
+
 static void
 ail_initialize_twiddled(struct ail_layout *layout)
 {
    unsigned offset_B = 0;
-   unsigned blocksize_B = util_format_get_blocksize(layout->format);
-
+   unsigned blocksize_B = ail_get_block_size_B(layout);
    unsigned w_el = util_format_get_nblocksx(layout->format, layout->width_px);
    unsigned h_el = util_format_get_nblocksy(layout->format, layout->height_px);
 
@@ -161,6 +177,8 @@ ail_make_miptree(struct ail_layout *layout)
    if (layout->tiling == AIL_TILING_LINEAR) {
       assert(layout->depth_px == 1 && "Invalid linear layout");
       assert(layout->levels == 1 && "Invalid linear layout");
+      assert(layout->sample_count_sa == 1 &&
+             "Multisampled linear layouts not supported");
       assert(util_format_get_blockwidth(layout->format) == 1 &&
             "Strided linear block formats unsupported");
       assert(util_format_get_blockheight(layout->format) == 1 &&
@@ -169,6 +187,7 @@ ail_make_miptree(struct ail_layout *layout)
       assert(layout->linear_stride_B == 0 && "Invalid nonlinear layout");
       assert(layout->depth_px >= 1 && "Invalid dimensions");
       assert(layout->levels >= 1 && "Invalid dimensions");
+      assert(layout->sample_count_sa >= 1 && "Invalid samplt count");
    }
 
    assert(util_format_get_blockdepth(layout->format) == 1 &&

src/asahi/layout/layout.h

@@ -68,6 +68,9 @@ struct ail_layout {
    /** Width, height, and depth in pixels at level 0 */
    uint32_t width_px, height_px, depth_px;
 
+   /** Number of samples per pixel. 1 if multisampling is disabled. */
+   uint8_t sample_count_sa;
+
    /** Number of miplevels. 1 if no mipmapping is used. */
    uint8_t levels;
 
@@ -164,6 +167,8 @@ ail_get_linear_pixel_B(struct ail_layout *layout, ASSERTED unsigned level,
          "Strided linear block formats unsupported");
    assert(util_format_get_blockheight(layout->format) == 1 &&
          "Strided linear block formats unsupported");
+   assert(layout->sample_count_sa == 1 &&
+          "Strided linear multisampling unsupported");
 
    return (y_px * ail_get_linear_stride_B(layout, level)) +
           (x_px * util_format_get_blocksize(layout->format));

src/asahi/layout/tests/test-layout.cpp

@@ -30,6 +30,7 @@ TEST(Cubemap, Nonmipmapped)
       .width_px = 512,
       .height_px = 512,
       .depth_px = 6,
+      .sample_count_sa = 1,
       .levels = 1,
       .tiling = AIL_TILING_TWIDDLED,
       .format = PIPE_FORMAT_R8G8B8A8_UNORM,
@@ -47,6 +48,7 @@ TEST(Miptree, SmokeTestBuffer)
       .width_px = 81946,
       .height_px = 1,
       .depth_px = 1,
+      .sample_count_sa = 1,
       .levels = 1,
       .tiling = AIL_TILING_LINEAR,
       .format = PIPE_FORMAT_R8_UINT,
@@ -1299,6 +1301,7 @@ TEST(Miptree, Tests2D)
          .width_px = test.width,
          .height_px = test.height,
          .depth_px = 1,
+         .sample_count_sa = 1,
          .levels = test.levels,
          .tiling = AIL_TILING_TWIDDLED,
          .format = test.format,

src/gallium/drivers/asahi/agx_pipe.c

@@ -147,6 +147,7 @@ agx_resource_setup(struct agx_device *dev,
       .width_px = templ->width0,
       .height_px = templ->height0,
       .depth_px = templ->depth0 * templ->array_size,
+      .sample_count_sa = MAX2(templ->nr_samples, 1),
       .levels = templ->last_level + 1,
    };
 }