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