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 
get_fidvid(uint32_t cpu,uint32_t * fid,uint32_t * vid)27 static 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;
49 err1:
50 	close(fd);
51 out:
52 	return err;
53 }
54 
55 
56 /* Return a frequency in MHz, given an input fid */
find_freq_from_fid(uint32_t fid)57 static 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 */
find_millivolts_from_vid(uint32_t vid)63 static uint32_t find_millivolts_from_vid(uint32_t vid)
64 {
65 	return 1550-vid*25;
66 }
67 
main(int argc,char * argv[])68 int 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