1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * (C) 2004 Bruno Ducrot <ducrot@poupinou.org>
4 *
5 * Based on code found in
6 * linux/arch/i386/kernel/cpu/cpufreq/powernow-k8.c
7 * and originally developed by Paul Devriendt
8 */
9
10#include <stdio.h>
11#include <stdlib.h>
12#include <stdint.h>
13#include <unistd.h>
14#include <errno.h>
15#include <fcntl.h>
16
17#include <sys/types.h>
18#include <sys/stat.h>
19
20#define MCPU 32
21
22#define MSR_FIDVID_STATUS 0xc0010042
23
24#define MSR_S_HI_CURRENT_VID 0x0000001f
25#define MSR_S_LO_CURRENT_FID 0x0000003f
26
27static int get_fidvid(uint32_t cpu, uint32_t *fid, uint32_t *vid)
28{
29 int err = 1;
30 uint64_t msr = 0;
31 int fd;
32 char file[20];
33
34 if (cpu > MCPU)
35 goto out;
36
37 sprintf(file, "/dev/cpu/%d/msr", cpu);
38
39 fd = open(file, O_RDONLY);
40 if (fd < 0)
41 goto out;
42 lseek(fd, MSR_FIDVID_STATUS, SEEK_CUR);
43 if (read(fd, &msr, 8) != 8)
44 goto err1;
45
46 *fid = ((uint32_t )(msr & 0xffffffffull)) & MSR_S_LO_CURRENT_FID;
47 *vid = ((uint32_t )(msr>>32 & 0xffffffffull)) & MSR_S_HI_CURRENT_VID;
48 err = 0;
49err1:
50 close(fd);
51out:
52 return err;
53}
54
55
56/* Return a frequency in MHz, given an input fid */
57static uint32_t find_freq_from_fid(uint32_t fid)
58{
59 return 800 + (fid * 100);
60}
61
62/* Return a voltage in miliVolts, given an input vid */
63static uint32_t find_millivolts_from_vid(uint32_t vid)
64{
65 return 1550-vid*25;
66}
67
68int main (int argc, char *argv[])
69{
70 int err;
71 int cpu;
72 uint32_t fid, vid;
73
74 if (argc < 2)
75 cpu = 0;
76 else
77 cpu = strtoul(argv[1], NULL, 0);
78
79 err = get_fidvid(cpu, &fid, &vid);
80
81 if (err) {
82 printf("can't get fid, vid from MSR\n");
83 printf("Possible trouble: you don't run a powernow-k8 capable cpu\n");
84 printf("or you are not root, or the msr driver is not present\n");
85 exit(1);
86 }
87
88
89 printf("cpu %d currently at %d MHz and %d mV\n",
90 cpu,
91 find_freq_from_fid(fid),
92 find_millivolts_from_vid(vid));
93
94 return 0;
95}
96

source code of linux/tools/power/cpupower/debug/i386/powernow-k8-decode.c