1// SPDX-License-Identifier: MIT
2/*
3 * Copyright 2023 Advanced Micro Devices, Inc.
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be included in
13 * all copies or substantial portions of the 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 COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
19 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
20 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
21 * OTHER DEALINGS IN THE SOFTWARE.
22 *
23 * Authors: AMD
24 *
25 */
26#include "dm_services.h"
27#include "custom_float.h"
28
29static bool build_custom_float(struct fixed31_32 value,
30 const struct custom_float_format *format,
31 bool *negative,
32 uint32_t *mantissa,
33 uint32_t *exponenta)
34{
35 uint32_t exp_offset = (1 << (format->exponenta_bits - 1)) - 1;
36
37 const struct fixed31_32 mantissa_constant_plus_max_fraction =
38 dc_fixpt_from_fraction(numerator: (1LL << (format->mantissa_bits + 1)) - 1,
39 denominator: 1LL << format->mantissa_bits);
40
41 struct fixed31_32 mantiss;
42
43 if (dc_fixpt_eq(arg1: value, arg2: dc_fixpt_zero)) {
44 *negative = false;
45 *mantissa = 0;
46 *exponenta = 0;
47 return true;
48 }
49
50 if (dc_fixpt_lt(arg1: value, arg2: dc_fixpt_zero)) {
51 *negative = format->sign;
52 value = dc_fixpt_neg(arg: value);
53 } else {
54 *negative = false;
55 }
56
57 if (dc_fixpt_lt(arg1: value, arg2: dc_fixpt_one)) {
58 uint32_t i = 1;
59
60 do {
61 value = dc_fixpt_shl(arg: value, shift: 1);
62 ++i;
63 } while (dc_fixpt_lt(arg1: value, arg2: dc_fixpt_one));
64
65 --i;
66
67 if (exp_offset <= i) {
68 *mantissa = 0;
69 *exponenta = 0;
70 return true;
71 }
72
73 *exponenta = exp_offset - i;
74 } else if (dc_fixpt_le(arg1: mantissa_constant_plus_max_fraction, arg2: value)) {
75 uint32_t i = 1;
76
77 do {
78 value = dc_fixpt_shr(arg: value, shift: 1);
79 ++i;
80 } while (dc_fixpt_lt(arg1: mantissa_constant_plus_max_fraction, arg2: value));
81
82 *exponenta = exp_offset + i - 1;
83 } else {
84 *exponenta = exp_offset;
85 }
86
87 mantiss = dc_fixpt_sub(arg1: value, arg2: dc_fixpt_one);
88
89 if (dc_fixpt_lt(arg1: mantiss, arg2: dc_fixpt_zero) ||
90 dc_fixpt_lt(arg1: dc_fixpt_one, arg2: mantiss))
91 mantiss = dc_fixpt_zero;
92 else
93 mantiss = dc_fixpt_shl(arg: mantiss, shift: format->mantissa_bits);
94
95 *mantissa = dc_fixpt_floor(arg: mantiss);
96
97 return true;
98}
99
100static bool setup_custom_float(const struct custom_float_format *format,
101 bool negative,
102 uint32_t mantissa,
103 uint32_t exponenta,
104 uint32_t *result)
105{
106 uint32_t i = 0;
107 uint32_t j = 0;
108 uint32_t value = 0;
109
110 /* verification code:
111 * once calculation is ok we can remove it
112 */
113
114 const uint32_t mantissa_mask =
115 (1 << (format->mantissa_bits + 1)) - 1;
116
117 const uint32_t exponenta_mask =
118 (1 << (format->exponenta_bits + 1)) - 1;
119
120 if (mantissa & ~mantissa_mask) {
121 BREAK_TO_DEBUGGER();
122 mantissa = mantissa_mask;
123 }
124
125 if (exponenta & ~exponenta_mask) {
126 BREAK_TO_DEBUGGER();
127 exponenta = exponenta_mask;
128 }
129
130 /* end of verification code */
131
132 while (i < format->mantissa_bits) {
133 uint32_t mask = 1 << i;
134
135 if (mantissa & mask)
136 value |= mask;
137
138 ++i;
139 }
140
141 while (j < format->exponenta_bits) {
142 uint32_t mask = 1 << j;
143
144 if (exponenta & mask)
145 value |= mask << i;
146
147 ++j;
148 }
149
150 if (negative && format->sign)
151 value |= 1 << (i + j);
152
153 *result = value;
154
155 return true;
156}
157
158bool convert_to_custom_float_format(struct fixed31_32 value,
159 const struct custom_float_format *format,
160 uint32_t *result)
161{
162 uint32_t mantissa;
163 uint32_t exponenta;
164 bool negative;
165
166 return build_custom_float(value, format, negative: &negative, mantissa: &mantissa, exponenta: &exponenta) &&
167 setup_custom_float(format,
168 negative,
169 mantissa,
170 exponenta,
171 result);
172}
173
174

source code of linux/drivers/gpu/drm/amd/display/dc/basics/custom_float.c