src/gallium/drivers/panfrost/pan_afbc.c

   1 /*
   2  * Copyright (C) 2019 Collabora, Ltd.
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  21  * SOFTWARE.
  22  *
  23  * Authors:
  24  *   Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
  25  */
  26
  27 #include "pan_resource.h"
  28 #include "util/format/u_format.h"
  29
  30 /* Arm FrameBuffer Compression (AFBC) is a lossless compression scheme natively
  31  * implemented in Mali GPUs (as well as many display controllers paired with
  32  * Mali GPUs, etc). Where possible, Panfrost prefers to use AFBC for both
  33  * rendering and texturing. In most cases, this is a performance-win due to a
  34  * dramatic reduction in memory bandwidth and cache locality compared to a
  35  * linear resources.
  36  *
  37  * AFBC divides the framebuffer into 16x16 tiles (other sizes possible, TODO:
  38  * do we need to support this?). So, the width and height each must be aligned
  39  * up to 16 pixels. This is inherently good for performance; note that for a 4
  40  * byte-per-pixel format like RGBA8888, that means that rows are 16*4=64 byte
  41  * aligned, which is the cache-line size.
  42  *
  43  * For each AFBC-compressed resource, there is a single contiguous
  44  * (CPU/GPU-shared) buffer. This buffer itself is divided into two parts:
  45  * header and body, placed immediately after each other.
  46  *
  47  * The AFBC header contains 16 bytes of metadata per tile.
  48  *
  49  * The AFBC body is the same size as the original linear resource (padded to
  50  * the nearest tile). Although the body comes immediately after the header, it
  51  * must also be cache-line aligned, so there can sometimes be a bit of padding
  52  * between the header and body.
  53  *
  54  * As an example, a 64x64 RGBA framebuffer contains 64/16 = 4 tiles horizontally and
  55  * 4 tiles vertically. There are 4*4=16 tiles in total, each containing 16
  56  * bytes of metadata, so there is a 16*16=256 byte header. 64x64 is already
  57  * tile aligned, so the body is 64*64 * 4 bytes per pixel = 16384 bytes of
  58  * body.
  59  *
  60  * From userspace, Panfrost needs to be able to calculate these sizes. It
  61  * explicitly does not and can not know the format of the data contained within
  62  * this header and body. The GPU has native support for AFBC encode/decode. For
  63  * an internal FBO or a framebuffer used for scanout with an AFBC-compatible
  64  * winsys/display-controller, the buffer is maintained AFBC throughout flight,
  65  * and the driver never needs to know the internal data. For edge cases where
  66  * the driver really does need to read/write from the AFBC resource, we
  67  * generate a linear staging buffer and use the GPU to blit AFBC<--->linear.
  68  * TODO: Implement me. */
  69
  70 #define AFBC_TILE_WIDTH 16
  71 #define AFBC_TILE_HEIGHT 16
  72 #define AFBC_HEADER_BYTES_PER_TILE 16
  73 #define AFBC_CACHE_ALIGN 64
  74
  75 /* Is it possible to AFBC compress a particular format? Common formats (and
  76  * YUV) are compressible. Some obscure formats are not and fallback on linear,
  77  * at a performance hit. Also, if you need to disable AFBC entirely in the
  78  * driver for debug/profiling, just always return false here. */
  79
  80 bool
  81 panfrost_format_supports_afbc(enum pipe_format format)
  82 {
  83         const struct util_format_description *desc =
  84                 util_format_description(format);
  85
  86         /* sRGB cannot be AFBC, but it can be tiled. TODO: Verify. The blob
  87          * does not do AFBC for SRGB8_ALPHA8, but it's not clear why it
  88          * shouldn't be able to. */
  89
  90         if (desc->colorspace == UTIL_FORMAT_COLORSPACE_SRGB)
  91                 return false;
  92
  93         if (util_format_is_rgba8_variant(desc))
  94                 return true;
  95
  96         /* Z32/Z16/S8 are all compressible as well, but they are implemented as
  97          * Z24S8 with wasted bits. So Z24S8 is the only format we actually need
  98          * to handle compressed, and we can make the state tracker deal with
  99          * the rest. */
 100
 101         if (format == PIPE_FORMAT_Z24_UNORM_S8_UINT)
 102                 return true;
 103
 104         /* TODO: AFBC of other formats */
 105
 106         return false;
 107 }
 108
 109 unsigned
 110 panfrost_afbc_header_size(unsigned width, unsigned height)
 111 {
 112         /* Align to tile */
 113         unsigned aligned_width  = ALIGN_POT(width,  AFBC_TILE_WIDTH);
 114         unsigned aligned_height = ALIGN_POT(height, AFBC_TILE_HEIGHT);
 115
 116         /* Compute size in tiles, rather than pixels */
 117         unsigned tile_count_x = aligned_width  / AFBC_TILE_WIDTH;
 118         unsigned tile_count_y = aligned_height / AFBC_TILE_HEIGHT;
 119         unsigned tile_count = tile_count_x * tile_count_y;
 120
 121         /* Multiply to find the header size */
 122         unsigned header_bytes = tile_count * AFBC_HEADER_BYTES_PER_TILE;
 123
 124         /* Align and go */
 125         return ALIGN_POT(header_bytes, AFBC_CACHE_ALIGN);
 126
 127 }