1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *  (C) 2003 - 2004  Dominik Brodowski <linux@dominikbrodowski.de>
4 *
5 * Based on code found in
6 * linux/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c
7 * and originally developed by Jeremy Fitzhardinge.
8 *
9 * USAGE: simply run it to decode the current settings on CPU 0,
10 *	  or pass the CPU number as argument, or pass the MSR content
11 *	  as argument.
12 */
13
14#include <stdio.h>
15#include <stdlib.h>
16#include <stdint.h>
17#include <unistd.h>
18#include <errno.h>
19#include <fcntl.h>
20
21#include <sys/types.h>
22#include <sys/stat.h>
23
24#define MCPU	32
25
26#define MSR_IA32_PERF_STATUS	0x198
27
28static int rdmsr(unsigned int cpu, unsigned int msr,
29		 unsigned int *lo, unsigned int *hi)
30{
31	int fd;
32	char file[20];
33	unsigned long long val;
34	int retval = -1;
35
36	*lo = *hi = 0;
37
38	if (cpu > MCPU)
39		goto err1;
40
41	sprintf(file, "/dev/cpu/%d/msr", cpu);
42	fd = open(file, O_RDONLY);
43
44	if (fd < 0)
45		goto err1;
46
47	if (lseek(fd, msr, SEEK_CUR) == -1)
48		goto err2;
49
50	if (read(fd, &val, 8) != 8)
51		goto err2;
52
53	*lo = (uint32_t )(val & 0xffffffffull);
54	*hi = (uint32_t )(val>>32 & 0xffffffffull);
55
56	retval = 0;
57err2:
58	close(fd);
59err1:
60	return retval;
61}
62
63static void decode (unsigned int msr)
64{
65	unsigned int multiplier;
66	unsigned int mv;
67
68	multiplier = ((msr >> 8) & 0xFF);
69
70	mv = (((msr & 0xFF) * 16) + 700);
71
72	printf("0x%x means multiplier %d @ %d mV\n", msr, multiplier, mv);
73}
74
75static int decode_live(unsigned int cpu)
76{
77	unsigned int lo, hi;
78	int err;
79
80	err = rdmsr(cpu, MSR_IA32_PERF_STATUS, &lo, &hi);
81
82	if (err) {
83		printf("can't get MSR_IA32_PERF_STATUS for cpu %d\n", cpu);
84		printf("Possible trouble: you don't run an Enhanced SpeedStep capable cpu\n");
85		printf("or you are not root, or the msr driver is not present\n");
86		return 1;
87	}
88
89	decode(lo);
90
91	return 0;
92}
93
94int main (int argc, char **argv)
95{
96	unsigned int cpu, mode = 0;
97
98	if (argc < 2)
99		cpu = 0;
100	else {
101		cpu = strtoul(argv[1], NULL, 0);
102		if (cpu >= MCPU)
103			mode = 1;
104	}
105
106	if (mode)
107		decode(cpu);
108	else
109		decode_live(cpu);
110
111	return 0;
112}
113