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 */
24
25 #include "util/u_math.h"
26 #include "pan_encoder.h"
27
28 /* This file handles attribute descriptors. The
29 * bulk of the complexity is from instancing. See mali_job for
30 * notes on how this works. But basically, for small vertex
31 * counts, we have a lookup table, and for large vertex counts,
32 * we look at the high bits as a heuristic. This has to match
33 * exactly how the hardware calculates this (which is why the
34 * algorithm is so weird) or else instancing will break. */
35
36 /* Given an odd number (of the form 2k + 1), compute k */
37 #define ODD(odd) ((odd - 1) >> 1)
38
39 static unsigned
panfrost_small_padded_vertex_count(unsigned idx)40 panfrost_small_padded_vertex_count(unsigned idx)
41 {
42 if (idx < 10)
43 return idx;
44 else
45 return (idx + 1) & ~1;
46 }
47
48 static unsigned
panfrost_large_padded_vertex_count(uint32_t vertex_count)49 panfrost_large_padded_vertex_count(uint32_t vertex_count)
50 {
51 /* First, we have to find the highest set one */
52 unsigned highest = 32 - __builtin_clz(vertex_count);
53
54 /* Using that, we mask out the highest 4-bits */
55 unsigned n = highest - 4;
56 unsigned nibble = (vertex_count >> n) & 0xF;
57
58 /* Great, we have the nibble. Now we can just try possibilities. Note
59 * that we don't care about the bottom most bit in most cases, and we
60 * know the top bit must be 1 */
61
62 unsigned middle_two = (nibble >> 1) & 0x3;
63
64 switch (middle_two) {
65 case 0b00:
66 if (!(nibble & 1))
67 return (1 << n) * 9;
68 else
69 return (1 << (n + 1)) * 5;
70 case 0b01:
71 return (1 << (n + 2)) * 3;
72 case 0b10:
73 return (1 << (n + 1)) * 7;
74 case 0b11:
75 return (1 << (n + 4));
76 default:
77 return 0; /* unreachable */
78 }
79 }
80
81 unsigned
panfrost_padded_vertex_count(unsigned vertex_count)82 panfrost_padded_vertex_count(unsigned vertex_count)
83 {
84 if (vertex_count < 20)
85 return panfrost_small_padded_vertex_count(vertex_count);
86 else
87 return panfrost_large_padded_vertex_count(vertex_count);
88 }
89
90 /* The much, much more irritating case -- instancing is enabled. See
91 * panfrost_job.h for notes on how this works */
92
93 unsigned
panfrost_compute_magic_divisor(unsigned hw_divisor,unsigned * o_shift,unsigned * extra_flags)94 panfrost_compute_magic_divisor(unsigned hw_divisor, unsigned *o_shift, unsigned *extra_flags)
95 {
96 /* We have a NPOT divisor. Here's the fun one (multipling by
97 * the inverse and shifting) */
98
99 /* floor(log2(d)) */
100 unsigned shift = util_logbase2(hw_divisor);
101
102 /* m = ceil(2^(32 + shift) / d) */
103 uint64_t shift_hi = 32 + shift;
104 uint64_t t = 1ll << shift_hi;
105 double t_f = t;
106 double hw_divisor_d = hw_divisor;
107 double m_f = ceil(t_f / hw_divisor_d);
108 unsigned m = m_f;
109
110 /* Default case */
111 uint32_t magic_divisor = m;
112
113 /* e = 2^(shift + 32) % d */
114 uint64_t e = t % hw_divisor;
115
116 /* Apply round-down algorithm? e <= 2^shift?. XXX: The blob
117 * seems to use a different condition */
118 if (e <= (1ll << shift)) {
119 magic_divisor = m - 1;
120 *extra_flags = 1;
121 }
122
123 /* Top flag implicitly set */
124 assert(magic_divisor & (1u << 31));
125 magic_divisor &= ~(1u << 31);
126 *o_shift = shift;
127
128 return magic_divisor;
129 }
130