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_texture.h"
28
29 /* Arm FrameBuffer Compression (AFBC) is a lossless compression scheme natively
30 * implemented in Mali GPUs (as well as many display controllers paired with
31 * Mali GPUs, etc). Where possible, Panfrost prefers to use AFBC for both
32 * rendering and texturing. In most cases, this is a performance-win due to a
33 * dramatic reduction in memory bandwidth and cache locality compared to a
34 * linear resources.
35 *
36 * AFBC divides the framebuffer into 16x16 tiles (other sizes possible, TODO:
37 * do we need to support this?). So, the width and height each must be aligned
38 * up to 16 pixels. This is inherently good for performance; note that for a 4
39 * byte-per-pixel format like RGBA8888, that means that rows are 16*4=64 byte
40 * aligned, which is the cache-line size.
41 *
42 * For each AFBC-compressed resource, there is a single contiguous
43 * (CPU/GPU-shared) buffer. This buffer itself is divided into two parts:
44 * header and body, placed immediately after each other.
45 *
46 * The AFBC header contains 16 bytes of metadata per tile.
47 *
48 * The AFBC body is the same size as the original linear resource (padded to
49 * the nearest tile). Although the body comes immediately after the header, it
50 * must also be cache-line aligned, so there can sometimes be a bit of padding
51 * between the header and body.
52 *
53 * As an example, a 64x64 RGBA framebuffer contains 64/16 = 4 tiles horizontally and
54 * 4 tiles vertically. There are 4*4=16 tiles in total, each containing 16
55 * bytes of metadata, so there is a 16*16=256 byte header. 64x64 is already
56 * tile aligned, so the body is 64*64 * 4 bytes per pixel = 16384 bytes of
57 * body.
58 *
59 * From userspace, Panfrost needs to be able to calculate these sizes. It
60 * explicitly does not and can not know the format of the data contained within
61 * this header and body. The GPU has native support for AFBC encode/decode. For
62 * an internal FBO or a framebuffer used for scanout with an AFBC-compatible
63 * winsys/display-controller, the buffer is maintained AFBC throughout flight,
64 * and the driver never needs to know the internal data. For edge cases where
65 * the driver really does need to read/write from the AFBC resource, we
66 * generate a linear staging buffer and use the GPU to blit AFBC<--->linear.
67 * TODO: Implement me. */
68
69 #define AFBC_TILE_WIDTH 16
70 #define AFBC_TILE_HEIGHT 16
71 #define AFBC_HEADER_BYTES_PER_TILE 16
72 #define AFBC_CACHE_ALIGN 64
73
74 /* Is it possible to AFBC compress a particular format? Common formats (and
75 * YUV) are compressible. Some obscure formats are not and fallback on linear,
76 * at a performance hit. Also, if you need to disable AFBC entirely in the
77 * driver for debug/profiling, just always return false here. */
78
79 bool
panfrost_format_supports_afbc(enum pipe_format format)80 panfrost_format_supports_afbc(enum pipe_format format)
81 {
82 const struct util_format_description *desc =
83 util_format_description(format);
84
85 /* sRGB cannot be AFBC, but it can be tiled. TODO: Verify. The blob
86 * does not do AFBC for SRGB8_ALPHA8, but it's not clear why it
87 * shouldn't be able to. */
88
89 if (desc->colorspace == UTIL_FORMAT_COLORSPACE_SRGB)
90 return false;
91
92 if (util_format_is_rgba8_variant(desc))
93 return true;
94
95 switch (format) {
96 case PIPE_FORMAT_R8G8B8_UNORM:
97 case PIPE_FORMAT_B8G8R8_UNORM:
98 case PIPE_FORMAT_R5G6B5_UNORM:
99 case PIPE_FORMAT_B5G6R5_UNORM:
100 case PIPE_FORMAT_Z24_UNORM_S8_UINT:
101 case PIPE_FORMAT_Z24X8_UNORM:
102 case PIPE_FORMAT_Z16_UNORM:
103 return true;
104 default:
105 return false;
106 }
107 }
108
109 unsigned
panfrost_afbc_header_size(unsigned width,unsigned height)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 }
128
129 /* The lossless colour transform (AFBC_FORMAT_MOD_YTR) requires RGB. */
130
131 bool
panfrost_afbc_can_ytr(enum pipe_format format)132 panfrost_afbc_can_ytr(enum pipe_format format)
133 {
134 const struct util_format_description *desc =
135 util_format_description(format);
136
137 /* YTR is only defined for RGB(A) */
138 if (desc->nr_channels != 3 && desc->nr_channels != 4)
139 return false;
140
141 /* The fourth channel if it exists doesn't matter */
142 return desc->colorspace == UTIL_FORMAT_COLORSPACE_RGB;
143 }
144