xref: /openbmc/linux/kernel/time/timeconst.bc (revision 35728b82)
1/* SPDX-License-Identifier: GPL-2.0 */
2
3scale=0
4
5define gcd(a,b) {
6	auto t;
7	while (b) {
8		t = b;
9		b = a % b;
10		a = t;
11	}
12	return a;
13}
14
15/* Division by reciprocal multiplication. */
16define fmul(b,n,d) {
17       return (2^b*n+d-1)/d;
18}
19
20/* Adjustment factor when a ceiling value is used.  Use as:
21   (imul * n) + (fmulxx * n + fadjxx) >> xx) */
22define fadj(b,n,d) {
23	auto v;
24	d = d/gcd(n,d);
25	v = 2^b*(d-1)/d;
26	return v;
27}
28
29/* Compute the appropriate mul/adj values as well as a shift count,
30   which brings the mul value into the range 2^b-1 <= x < 2^b.  Such
31   a shift value will be correct in the signed integer range and off
32   by at most one in the upper half of the unsigned range. */
33define fmuls(b,n,d) {
34	auto s, m;
35	for (s = 0; 1; s++) {
36		m = fmul(s,n,d);
37		if (m >= 2^(b-1))
38			return s;
39	}
40	return 0;
41}
42
43define timeconst(hz) {
44	print "/* Automatically generated by kernel/time/timeconst.bc */\n"
45	print "/* Time conversion constants for HZ == ", hz, " */\n"
46	print "\n"
47
48	print "#ifndef KERNEL_TIMECONST_H\n"
49	print "#define KERNEL_TIMECONST_H\n\n"
50
51	print "#include <linux/param.h>\n"
52	print "#include <linux/types.h>\n\n"
53
54	print "#if HZ != ", hz, "\n"
55	print "#error \qinclude/generated/timeconst.h has the wrong HZ value!\q\n"
56	print "#endif\n\n"
57
58	if (hz < 2) {
59		print "#error Totally bogus HZ value!\n"
60	} else {
61		s=fmuls(32,1000,hz)
62		obase=16
63		print "#define HZ_TO_MSEC_MUL32\tU64_C(0x", fmul(s,1000,hz), ")\n"
64		print "#define HZ_TO_MSEC_ADJ32\tU64_C(0x", fadj(s,1000,hz), ")\n"
65		obase=10
66		print "#define HZ_TO_MSEC_SHR32\t", s, "\n"
67
68		s=fmuls(32,hz,1000)
69		obase=16
70		print "#define MSEC_TO_HZ_MUL32\tU64_C(0x", fmul(s,hz,1000), ")\n"
71		print "#define MSEC_TO_HZ_ADJ32\tU64_C(0x", fadj(s,hz,1000), ")\n"
72		obase=10
73		print "#define MSEC_TO_HZ_SHR32\t", s, "\n"
74
75		obase=10
76		cd=gcd(hz,1000)
77		print "#define HZ_TO_MSEC_NUM\t\t", 1000/cd, "\n"
78		print "#define HZ_TO_MSEC_DEN\t\t", hz/cd, "\n"
79		print "#define MSEC_TO_HZ_NUM\t\t", hz/cd, "\n"
80		print "#define MSEC_TO_HZ_DEN\t\t", 1000/cd, "\n"
81		print "\n"
82
83		s=fmuls(32,1000000,hz)
84		obase=16
85		print "#define HZ_TO_USEC_MUL32\tU64_C(0x", fmul(s,1000000,hz), ")\n"
86		print "#define HZ_TO_USEC_ADJ32\tU64_C(0x", fadj(s,1000000,hz), ")\n"
87		obase=10
88		print "#define HZ_TO_USEC_SHR32\t", s, "\n"
89
90		s=fmuls(32,hz,1000000)
91		obase=16
92		print "#define USEC_TO_HZ_MUL32\tU64_C(0x", fmul(s,hz,1000000), ")\n"
93		print "#define USEC_TO_HZ_ADJ32\tU64_C(0x", fadj(s,hz,1000000), ")\n"
94		obase=10
95		print "#define USEC_TO_HZ_SHR32\t", s, "\n"
96
97		obase=10
98		cd=gcd(hz,1000000)
99		print "#define HZ_TO_USEC_NUM\t\t", 1000000/cd, "\n"
100		print "#define HZ_TO_USEC_DEN\t\t", hz/cd, "\n"
101		print "#define USEC_TO_HZ_NUM\t\t", hz/cd, "\n"
102		print "#define USEC_TO_HZ_DEN\t\t", 1000000/cd, "\n"
103
104		cd=gcd(hz,1000000000)
105		print "#define HZ_TO_NSEC_NUM\t\t", 1000000000/cd, "\n"
106		print "#define HZ_TO_NSEC_DEN\t\t", hz/cd, "\n"
107		print "#define NSEC_TO_HZ_NUM\t\t", hz/cd, "\n"
108		print "#define NSEC_TO_HZ_DEN\t\t", 1000000000/cd, "\n"
109		print "\n"
110
111		print "#endif /* KERNEL_TIMECONST_H */\n"
112	}
113	halt
114}
115
116hz = read();
117timeconst(hz)
118