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
rdmsr(unsigned int cpu,unsigned int msr,unsigned int * lo,unsigned int * hi)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
decode(unsigned int msr)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
decode_live(unsigned int cpu)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
main(int argc,char ** argv)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