1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0-only
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * (C) 2003 - 2004 Dominik Brodowski <linux@dominikbrodowski.de>
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Based on code found in
6*4882a593Smuzhiyun * linux/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c
7*4882a593Smuzhiyun * and originally developed by Jeremy Fitzhardinge.
8*4882a593Smuzhiyun *
9*4882a593Smuzhiyun * USAGE: simply run it to decode the current settings on CPU 0,
10*4882a593Smuzhiyun * or pass the CPU number as argument, or pass the MSR content
11*4882a593Smuzhiyun * as argument.
12*4882a593Smuzhiyun */
13*4882a593Smuzhiyun
14*4882a593Smuzhiyun #include <stdio.h>
15*4882a593Smuzhiyun #include <stdlib.h>
16*4882a593Smuzhiyun #include <stdint.h>
17*4882a593Smuzhiyun #include <unistd.h>
18*4882a593Smuzhiyun #include <errno.h>
19*4882a593Smuzhiyun #include <fcntl.h>
20*4882a593Smuzhiyun
21*4882a593Smuzhiyun #include <sys/types.h>
22*4882a593Smuzhiyun #include <sys/stat.h>
23*4882a593Smuzhiyun
24*4882a593Smuzhiyun #define MCPU 32
25*4882a593Smuzhiyun
26*4882a593Smuzhiyun #define MSR_IA32_PERF_STATUS 0x198
27*4882a593Smuzhiyun
rdmsr(unsigned int cpu,unsigned int msr,unsigned int * lo,unsigned int * hi)28*4882a593Smuzhiyun static int rdmsr(unsigned int cpu, unsigned int msr,
29*4882a593Smuzhiyun unsigned int *lo, unsigned int *hi)
30*4882a593Smuzhiyun {
31*4882a593Smuzhiyun int fd;
32*4882a593Smuzhiyun char file[20];
33*4882a593Smuzhiyun unsigned long long val;
34*4882a593Smuzhiyun int retval = -1;
35*4882a593Smuzhiyun
36*4882a593Smuzhiyun *lo = *hi = 0;
37*4882a593Smuzhiyun
38*4882a593Smuzhiyun if (cpu > MCPU)
39*4882a593Smuzhiyun goto err1;
40*4882a593Smuzhiyun
41*4882a593Smuzhiyun sprintf(file, "/dev/cpu/%d/msr", cpu);
42*4882a593Smuzhiyun fd = open(file, O_RDONLY);
43*4882a593Smuzhiyun
44*4882a593Smuzhiyun if (fd < 0)
45*4882a593Smuzhiyun goto err1;
46*4882a593Smuzhiyun
47*4882a593Smuzhiyun if (lseek(fd, msr, SEEK_CUR) == -1)
48*4882a593Smuzhiyun goto err2;
49*4882a593Smuzhiyun
50*4882a593Smuzhiyun if (read(fd, &val, 8) != 8)
51*4882a593Smuzhiyun goto err2;
52*4882a593Smuzhiyun
53*4882a593Smuzhiyun *lo = (uint32_t )(val & 0xffffffffull);
54*4882a593Smuzhiyun *hi = (uint32_t )(val>>32 & 0xffffffffull);
55*4882a593Smuzhiyun
56*4882a593Smuzhiyun retval = 0;
57*4882a593Smuzhiyun err2:
58*4882a593Smuzhiyun close(fd);
59*4882a593Smuzhiyun err1:
60*4882a593Smuzhiyun return retval;
61*4882a593Smuzhiyun }
62*4882a593Smuzhiyun
decode(unsigned int msr)63*4882a593Smuzhiyun static void decode (unsigned int msr)
64*4882a593Smuzhiyun {
65*4882a593Smuzhiyun unsigned int multiplier;
66*4882a593Smuzhiyun unsigned int mv;
67*4882a593Smuzhiyun
68*4882a593Smuzhiyun multiplier = ((msr >> 8) & 0xFF);
69*4882a593Smuzhiyun
70*4882a593Smuzhiyun mv = (((msr & 0xFF) * 16) + 700);
71*4882a593Smuzhiyun
72*4882a593Smuzhiyun printf("0x%x means multiplier %d @ %d mV\n", msr, multiplier, mv);
73*4882a593Smuzhiyun }
74*4882a593Smuzhiyun
decode_live(unsigned int cpu)75*4882a593Smuzhiyun static int decode_live(unsigned int cpu)
76*4882a593Smuzhiyun {
77*4882a593Smuzhiyun unsigned int lo, hi;
78*4882a593Smuzhiyun int err;
79*4882a593Smuzhiyun
80*4882a593Smuzhiyun err = rdmsr(cpu, MSR_IA32_PERF_STATUS, &lo, &hi);
81*4882a593Smuzhiyun
82*4882a593Smuzhiyun if (err) {
83*4882a593Smuzhiyun printf("can't get MSR_IA32_PERF_STATUS for cpu %d\n", cpu);
84*4882a593Smuzhiyun printf("Possible trouble: you don't run an Enhanced SpeedStep capable cpu\n");
85*4882a593Smuzhiyun printf("or you are not root, or the msr driver is not present\n");
86*4882a593Smuzhiyun return 1;
87*4882a593Smuzhiyun }
88*4882a593Smuzhiyun
89*4882a593Smuzhiyun decode(lo);
90*4882a593Smuzhiyun
91*4882a593Smuzhiyun return 0;
92*4882a593Smuzhiyun }
93*4882a593Smuzhiyun
main(int argc,char ** argv)94*4882a593Smuzhiyun int main (int argc, char **argv)
95*4882a593Smuzhiyun {
96*4882a593Smuzhiyun unsigned int cpu, mode = 0;
97*4882a593Smuzhiyun
98*4882a593Smuzhiyun if (argc < 2)
99*4882a593Smuzhiyun cpu = 0;
100*4882a593Smuzhiyun else {
101*4882a593Smuzhiyun cpu = strtoul(argv[1], NULL, 0);
102*4882a593Smuzhiyun if (cpu >= MCPU)
103*4882a593Smuzhiyun mode = 1;
104*4882a593Smuzhiyun }
105*4882a593Smuzhiyun
106*4882a593Smuzhiyun if (mode)
107*4882a593Smuzhiyun decode(cpu);
108*4882a593Smuzhiyun else
109*4882a593Smuzhiyun decode_live(cpu);
110*4882a593Smuzhiyun
111*4882a593Smuzhiyun return 0;
112*4882a593Smuzhiyun }
113