centrino-decode.c

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