1 /*
2  *  (C) 2003 - 2004  Dominik Brodowski <linux@dominikbrodowski.de>
3  *
4  *  Licensed under the terms of the GNU GPL License version 2.
5  *
6  * Based on code found in
7  * linux/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c
8  * and originally developed by Jeremy Fitzhardinge.
9  *
10  * USAGE: simply run it to decode the current settings on CPU 0,
11  *	  or pass the CPU number as argument, or pass the MSR content
12  *	  as argument.
13  */
14 
15 #include <stdio.h>
16 #include <stdlib.h>
17 #include <stdint.h>
18 #include <unistd.h>
19 #include <errno.h>
20 #include <fcntl.h>
21 
22 #include <sys/types.h>
23 #include <sys/stat.h>
24 
25 #define MCPU	32
26 
27 #define MSR_IA32_PERF_STATUS	0x198
28 
29 static int rdmsr(unsigned int cpu, unsigned int msr,
30 		 unsigned int *lo, unsigned int *hi)
31 {
32 	int fd;
33 	char file[20];
34 	unsigned long long val;
35 	int retval = -1;
36 
37 	*lo = *hi = 0;
38 
39 	if (cpu > MCPU)
40 		goto err1;
41 
42 	sprintf(file, "/dev/cpu/%d/msr", cpu);
43 	fd = open(file, O_RDONLY);
44 
45 	if (fd < 0)
46 		goto err1;
47 
48 	if (lseek(fd, msr, SEEK_CUR) == -1)
49 		goto err2;
50 
51 	if (read(fd, &val, 8) != 8)
52 		goto err2;
53 
54 	*lo = (uint32_t )(val & 0xffffffffull);
55 	*hi = (uint32_t )(val>>32 & 0xffffffffull);
56 
57 	retval = 0;
58 err2:
59 	close(fd);
60 err1:
61 	return retval;
62 }
63 
64 static void decode (unsigned int msr)
65 {
66 	unsigned int multiplier;
67 	unsigned int mv;
68 
69 	multiplier = ((msr >> 8) & 0xFF);
70 
71 	mv = (((msr & 0xFF) * 16) + 700);
72 
73 	printf("0x%x means multiplier %d @ %d mV\n", msr, multiplier, mv);
74 }
75 
76 static int decode_live(unsigned int cpu)
77 {
78 	unsigned int lo, hi;
79 	int err;
80 
81 	err = rdmsr(cpu, MSR_IA32_PERF_STATUS, &lo, &hi);
82 
83 	if (err) {
84 		printf("can't get MSR_IA32_PERF_STATUS for cpu %d\n", cpu);
85 		printf("Possible trouble: you don't run an Enhanced SpeedStep capable cpu\n");
86 		printf("or you are not root, or the msr driver is not present\n");
87 		return 1;
88 	}
89 
90 	decode(lo);
91 
92 	return 0;
93 }
94 
95 int main (int argc, char **argv)
96 {
97 	unsigned int cpu, mode = 0;
98 
99 	if (argc < 2)
100 		cpu = 0;
101 	else {
102 		cpu = strtoul(argv[1], NULL, 0);
103 		if (cpu >= MCPU)
104 			mode = 1;
105 	}
106 
107 	if (mode)
108 		decode(cpu);
109 	else
110 		decode_live(cpu);
111 
112 	return 0;
113 }
114