1/*	$NetBSD: amdgpu_custom_float.c,v 1.2 2021/12/18 23:45:01 riastradh Exp $	*/
2
3/*
4 * Copyright 2017 Advanced Micro Devices, Inc.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
19 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
20 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
21 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
22 * OTHER DEALINGS IN THE SOFTWARE.
23 *
24 * Authors: AMD
25 *
26 */
27#include <sys/cdefs.h>
28__KERNEL_RCSID(0, "$NetBSD: amdgpu_custom_float.c,v 1.2 2021/12/18 23:45:01 riastradh Exp $");
29
30#include "dm_services.h"
31#include "custom_float.h"
32
33
34static bool build_custom_float(
35	struct fixed31_32 value,
36	const struct custom_float_format *format,
37	bool *negative,
38	uint32_t *mantissa,
39	uint32_t *exponenta)
40{
41	uint32_t exp_offset = (1 << (format->exponenta_bits - 1)) - 1;
42
43	const struct fixed31_32 mantissa_constant_plus_max_fraction =
44		dc_fixpt_from_fraction(
45			(1LL << (format->mantissa_bits + 1)) - 1,
46			1LL << format->mantissa_bits);
47
48	struct fixed31_32 mantiss;
49
50	if (dc_fixpt_eq(
51		value,
52		dc_fixpt_zero)) {
53		*negative = false;
54		*mantissa = 0;
55		*exponenta = 0;
56		return true;
57	}
58
59	if (dc_fixpt_lt(
60		value,
61		dc_fixpt_zero)) {
62		*negative = format->sign;
63		value = dc_fixpt_neg(value);
64	} else {
65		*negative = false;
66	}
67
68	if (dc_fixpt_lt(
69		value,
70		dc_fixpt_one)) {
71		uint32_t i = 1;
72
73		do {
74			value = dc_fixpt_shl(value, 1);
75			++i;
76		} while (dc_fixpt_lt(
77			value,
78			dc_fixpt_one));
79
80		--i;
81
82		if (exp_offset <= i) {
83			*mantissa = 0;
84			*exponenta = 0;
85			return true;
86		}
87
88		*exponenta = exp_offset - i;
89	} else if (dc_fixpt_le(
90		mantissa_constant_plus_max_fraction,
91		value)) {
92		uint32_t i = 1;
93
94		do {
95			value = dc_fixpt_shr(value, 1);
96			++i;
97		} while (dc_fixpt_lt(
98			mantissa_constant_plus_max_fraction,
99			value));
100
101		*exponenta = exp_offset + i - 1;
102	} else {
103		*exponenta = exp_offset;
104	}
105
106	mantiss = dc_fixpt_sub(
107		value,
108		dc_fixpt_one);
109
110	if (dc_fixpt_lt(
111			mantiss,
112			dc_fixpt_zero) ||
113		dc_fixpt_lt(
114			dc_fixpt_one,
115			mantiss))
116		mantiss = dc_fixpt_zero;
117	else
118		mantiss = dc_fixpt_shl(
119			mantiss,
120			format->mantissa_bits);
121
122	*mantissa = dc_fixpt_floor(mantiss);
123
124	return true;
125}
126
127static bool setup_custom_float(
128	const struct custom_float_format *format,
129	bool negative,
130	uint32_t mantissa,
131	uint32_t exponenta,
132	uint32_t *result)
133{
134	uint32_t i = 0;
135	uint32_t j = 0;
136
137	uint32_t value = 0;
138
139	/* verification code:
140	 * once calculation is ok we can remove it
141	 */
142
143	const uint32_t mantissa_mask =
144		(1 << (format->mantissa_bits + 1)) - 1;
145
146	const uint32_t exponenta_mask =
147		(1 << (format->exponenta_bits + 1)) - 1;
148
149	if (mantissa & ~mantissa_mask) {
150		BREAK_TO_DEBUGGER();
151		mantissa = mantissa_mask;
152	}
153
154	if (exponenta & ~exponenta_mask) {
155		BREAK_TO_DEBUGGER();
156		exponenta = exponenta_mask;
157	}
158
159	/* end of verification code */
160
161	while (i < format->mantissa_bits) {
162		uint32_t mask = 1 << i;
163
164		if (mantissa & mask)
165			value |= mask;
166
167		++i;
168	}
169
170	while (j < format->exponenta_bits) {
171		uint32_t mask = 1 << j;
172
173		if (exponenta & mask)
174			value |= mask << i;
175
176		++j;
177	}
178
179	if (negative && format->sign)
180		value |= 1 << (i + j);
181
182	*result = value;
183
184	return true;
185}
186
187bool convert_to_custom_float_format(
188	struct fixed31_32 value,
189	const struct custom_float_format *format,
190	uint32_t *result)
191{
192	uint32_t mantissa;
193	uint32_t exponenta;
194	bool negative;
195
196	return build_custom_float(
197		value, format, &negative, &mantissa, &exponenta) &&
198	setup_custom_float(
199		format, negative, mantissa, exponenta, result);
200}
201
202
203