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// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>
#include "../../../util/debug.h"
#include "../../../util/tsc.h"
#include "cpuid.h"
u64 rdtsc(void)
{
unsigned int low, high;
asm volatile("rdtsc" : "=a" (low), "=d" (high));
return low | ((u64)high) << 32;
}
/*
* Derive the TSC frequency in Hz from the /proc/cpuinfo, for example:
* ...
* model name : Intel(R) Xeon(R) Gold 6154 CPU @ 3.00GHz
* ...
* will return 3000000000.
*/
static u64 cpuinfo_tsc_freq(void)
{
u64 result = 0;
FILE *cpuinfo;
char *line = NULL;
size_t len = 0;
cpuinfo = fopen("/proc/cpuinfo", "r");
if (!cpuinfo) {
pr_err("Failed to read /proc/cpuinfo for TSC frequency\n");
return 0;
}
while (getline(&line, &len, cpuinfo) > 0) {
if (!strncmp(line, "model name", 10)) {
char *pos = strstr(line + 11, " @ ");
double float_result;
if (pos && sscanf(pos, " @ %lfGHz", &float_result) == 1) {
float_result *= 1000000000;
result = (u64)float_result;
goto out;
}
}
}
out:
if (result == 0)
pr_err("Failed to find TSC frequency in /proc/cpuinfo\n");
free(line);
fclose(cpuinfo);
return result;
}
u64 arch_get_tsc_freq(void)
{
unsigned int a, b, c, d, lvl;
static bool cached;
static double tsc;
char vendor[16];
if (cached)
return tsc;
cached = true;
get_cpuid_0(vendor, &lvl);
if (!strstr(vendor, "Intel"))
return 0;
/*
* Don't support Time Stamp Counter and
* Nominal Core Crystal Clock Information Leaf.
*/
if (lvl < 0x15) {
tsc = cpuinfo_tsc_freq();
return tsc;
}
cpuid(0x15, 0, &a, &b, &c, &d);
/* TSC frequency is not enumerated */
if (!a || !b || !c) {
tsc = cpuinfo_tsc_freq();
return tsc;
}
tsc = (u64)c * (u64)b / (u64)a;
return tsc;
}
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