powernow-k8-decode.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  (C) 2004 Bruno Ducrot <[email protected]>
 *
 * Based on code found in
 * linux/arch/i386/kernel/cpu/cpufreq/powernow-k8.c
 * and originally developed by Paul Devriendt
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>

#include <sys/types.h>
#include <sys/stat.h>

#define MCPU 32

#define MSR_FIDVID_STATUS	0xc0010042

#define MSR_S_HI_CURRENT_VID	0x0000001f
#define MSR_S_LO_CURRENT_FID	0x0000003f

static int get_fidvid(uint32_t cpu, uint32_t *fid, uint32_t *vid)
{
	int err = 1;
	uint64_t msr = 0;
	int fd;
	char file[20];

	if (cpu > MCPU)
		goto out;

	sprintf(file, "/dev/cpu/%d/msr", cpu);

	fd = open(file, O_RDONLY);
	if (fd < 0)
		goto out;
	lseek(fd, MSR_FIDVID_STATUS, SEEK_CUR);
	if (read(fd, &msr, 8) != 8)
		goto err1;

	*fid = ((uint32_t )(msr & 0xffffffffull)) & MSR_S_LO_CURRENT_FID;
	*vid = ((uint32_t )(msr>>32 & 0xffffffffull)) & MSR_S_HI_CURRENT_VID;
	err = 0;
err1:
	close(fd);
out:
	return err;
}


/* Return a frequency in MHz, given an input fid */
static uint32_t find_freq_from_fid(uint32_t fid)
{
	return 800 + (fid * 100);
}

/* Return a voltage in miliVolts, given an input vid */
static uint32_t find_millivolts_from_vid(uint32_t vid)
{
	return 1550-vid*25;
}

int main (int argc, char *argv[])
{
	int err;
	int cpu;
	uint32_t fid, vid;

	if (argc < 2)
		cpu = 0;
	else
		cpu = strtoul(argv[1], NULL, 0);

	err = get_fidvid(cpu, &fid, &vid);

	if (err) {
		printf("can't get fid, vid from MSR\n");
		printf("Possible trouble: you don't run a powernow-k8 capable cpu\n");
		printf("or you are not root, or the msr driver is not present\n");
		exit(1);
	}

	
	printf("cpu %d currently at %d MHz and %d mV\n",
			cpu,
			find_freq_from_fid(fid),
			find_millivolts_from_vid(vid));
	
	return 0;
}