panfrost: Move pan_afbc.c to root

Now that PIPE formats are shared across Mesa, this well-documented piece
of code is a good fit for root panfrost, let's move it and get a little
closer to taming the mess of resources.

Signed-off-by: Alyssa Rosenzweig <[email protected]>
Reviewed-by: Boris Brezillon <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3858>

3 files changed, 136 insertions, 0 deletions

diff --git a/src/panfrost/encoder/meson.build b/src/panfrost/encoder/meson.build
index d1335ab8f02..650289586fa 100644
--- a/src/panfrost/encoder/meson.build
+++ b/src/panfrost/encoder/meson.build
@@ -22,6 +22,7 @@
 libpanfrost_encoder_files = files(
   'pan_encoder.h',
 
+  'pan_afbc.c',
   'pan_attributes.c',
   'pan_invocation.c',
   'pan_sampler.c',
diff --git a/src/panfrost/encoder/pan_afbc.c b/src/panfrost/encoder/pan_afbc.c
new file mode 100644
index 00000000000..f29020e15b8
--- /dev/null
+++ b/src/panfrost/encoder/pan_afbc.c
@@ -0,0 +1,126 @@
+/*
+ * Copyright (C) 2019 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * Authors:
+ *   Alyssa Rosenzweig <[email protected]>
+ */
+
+#include "pan_texture.h"
+
+/* Arm FrameBuffer Compression (AFBC) is a lossless compression scheme natively
+ * implemented in Mali GPUs (as well as many display controllers paired with
+ * Mali GPUs, etc). Where possible, Panfrost prefers to use AFBC for both
+ * rendering and texturing. In most cases, this is a performance-win due to a
+ * dramatic reduction in memory bandwidth and cache locality compared to a
+ * linear resources.
+ *
+ * AFBC divides the framebuffer into 16x16 tiles (other sizes possible, TODO:
+ * do we need to support this?). So, the width and height each must be aligned
+ * up to 16 pixels. This is inherently good for performance; note that for a 4
+ * byte-per-pixel format like RGBA8888, that means that rows are 16*4=64 byte
+ * aligned, which is the cache-line size.
+ *
+ * For each AFBC-compressed resource, there is a single contiguous
+ * (CPU/GPU-shared) buffer. This buffer itself is divided into two parts:
+ * header and body, placed immediately after each other.
+ *
+ * The AFBC header contains 16 bytes of metadata per tile.
+ *
+ * The AFBC body is the same size as the original linear resource (padded to
+ * the nearest tile). Although the body comes immediately after the header, it
+ * must also be cache-line aligned, so there can sometimes be a bit of padding
+ * between the header and body.
+ *
+ * As an example, a 64x64 RGBA framebuffer contains 64/16 = 4 tiles horizontally and
+ * 4 tiles vertically. There are 4*4=16 tiles in total, each containing 16
+ * bytes of metadata, so there is a 16*16=256 byte header. 64x64 is already
+ * tile aligned, so the body is 64*64 * 4 bytes per pixel = 16384 bytes of
+ * body.
+ *
+ * From userspace, Panfrost needs to be able to calculate these sizes. It
+ * explicitly does not and can not know the format of the data contained within
+ * this header and body. The GPU has native support for AFBC encode/decode. For
+ * an internal FBO or a framebuffer used for scanout with an AFBC-compatible
+ * winsys/display-controller, the buffer is maintained AFBC throughout flight,
+ * and the driver never needs to know the internal data. For edge cases where
+ * the driver really does need to read/write from the AFBC resource, we
+ * generate a linear staging buffer and use the GPU to blit AFBC<--->linear.
+ * TODO: Implement me. */
+
+#define AFBC_TILE_WIDTH 16
+#define AFBC_TILE_HEIGHT 16
+#define AFBC_HEADER_BYTES_PER_TILE 16
+#define AFBC_CACHE_ALIGN 64
+
+/* Is it possible to AFBC compress a particular format? Common formats (and
+ * YUV) are compressible. Some obscure formats are not and fallback on linear,
+ * at a performance hit. Also, if you need to disable AFBC entirely in the
+ * driver for debug/profiling, just always return false here. */
+
+bool
+panfrost_format_supports_afbc(enum pipe_format format)
+{
+        const struct util_format_description *desc =
+                util_format_description(format);
+
+        /* sRGB cannot be AFBC, but it can be tiled. TODO: Verify. The blob
+         * does not do AFBC for SRGB8_ALPHA8, but it's not clear why it
+         * shouldn't be able to. */
+
+        if (desc->colorspace == UTIL_FORMAT_COLORSPACE_SRGB)
+                return false;
+
+        if (util_format_is_rgba8_variant(desc))
+                return true;
+
+        /* Z32/Z16/S8 are all compressible as well, but they are implemented as
+         * Z24S8 with wasted bits. So Z24S8 is the only format we actually need
+         * to handle compressed, and we can make the state tracker deal with
+         * the rest. */
+
+        if (format == PIPE_FORMAT_Z24_UNORM_S8_UINT)
+                return true;
+
+        /* TODO: AFBC of other formats */
+
+        return false;
+}
+
+unsigned
+panfrost_afbc_header_size(unsigned width, unsigned height)
+{
+        /* Align to tile */
+        unsigned aligned_width  = ALIGN_POT(width,  AFBC_TILE_WIDTH);
+        unsigned aligned_height = ALIGN_POT(height, AFBC_TILE_HEIGHT);
+
+        /* Compute size in tiles, rather than pixels */
+        unsigned tile_count_x = aligned_width  / AFBC_TILE_WIDTH;
+        unsigned tile_count_y = aligned_height / AFBC_TILE_HEIGHT;
+        unsigned tile_count = tile_count_x * tile_count_y;
+
+        /* Multiply to find the header size */
+        unsigned header_bytes = tile_count * AFBC_HEADER_BYTES_PER_TILE;
+
+        /* Align and go */
+        return ALIGN_POT(header_bytes, AFBC_CACHE_ALIGN);
+
+}
diff --git a/src/panfrost/encoder/pan_texture.h b/src/panfrost/encoder/pan_texture.h
index 54b2e39122e..043fcc3af10 100644
--- a/src/panfrost/encoder/pan_texture.h
+++ b/src/panfrost/encoder/pan_texture.h
@@ -29,6 +29,7 @@
 #define __PAN_TEXTURE_H
 
 #include <stdbool.h>
+#include "util/format/u_format.h"
 
 struct panfrost_slice {
         unsigned offset;
@@ -54,4 +55,12 @@ panfrost_compute_checksum_size(
         unsigned width,
         unsigned height);
 
+/* AFBC */
+
+bool
+panfrost_format_supports_afbc(enum pipe_format format);
+
+unsigned
+panfrost_afbc_header_size(unsigned width, unsigned height);
+
 #endif