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/*
* 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 <alyssa.rosenzweig@collabora.com>
*/
#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 gallium frontend 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);
}
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