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