1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/types.h>
3 #include <math.h>
4 #include <string.h>
5 #include <stdlib.h>
6
7 #include "../../../util/debug.h"
8 #include "../../../util/tsc.h"
9 #include "cpuid.h"
10
11 u64 rdtsc(void)
12 {
13 unsigned int low, high;
14
15 asm volatile("rdtsc" : "=a" (low), "=d" (high));
16
17 return low | ((u64)high) << 32;
18 }
19
20 /*
21 * Derive the TSC frequency in Hz from the /proc/cpuinfo, for example:
22 * ...
23 * model name : Intel(R) Xeon(R) Gold 6154 CPU @ 3.00GHz
24 * ...
25 * will return 3000000000.
26 */
27 static double cpuinfo_tsc_freq(void)
28 {
29 double result = 0;
30 FILE *cpuinfo;
31 char *line = NULL;
32 size_t len = 0;
33
34 cpuinfo = fopen("/proc/cpuinfo", "r");
35 if (!cpuinfo) {
36 pr_err("Failed to read /proc/cpuinfo for TSC frequency\n");
37 return NAN;
38 }
39 while (getline(&line, &len, cpuinfo) > 0) {
40 if (!strncmp(line, "model name", 10)) {
41 char *pos = strstr(line + 11, " @ ");
42
43 if (pos && sscanf(pos, " @ %lfGHz", &result) == 1) {
44 result *= 1000000000;
45 goto out;
46 }
47 }
48 }
49 out:
50 if (fpclassify(result) == FP_ZERO)
51 pr_err("Failed to find TSC frequency in /proc/cpuinfo\n");
52
53 free(line);
54 fclose(cpuinfo);
55 return result;
56 }
57
58 double arch_get_tsc_freq(void)
59 {
60 unsigned int a, b, c, d, lvl;
61 static bool cached;
62 static double tsc;
63 char vendor[16];
64
65 if (cached)
66 return tsc;
67
68 cached = true;
69 get_cpuid_0(vendor, &lvl);
70 if (!strstr(vendor, "Intel"))
71 return 0;
72
73 /*
74 * Don't support Time Stamp Counter and
75 * Nominal Core Crystal Clock Information Leaf.
76 */
77 if (lvl < 0x15) {
78 tsc = cpuinfo_tsc_freq();
79 return tsc;
80 }
81
82 cpuid(0x15, 0, &a, &b, &c, &d);
83 /* TSC frequency is not enumerated */
84 if (!a || !b || !c) {
85 tsc = cpuinfo_tsc_freq();
86 return tsc;
87 }
88
89 tsc = (double)c * (double)b / (double)a;
90 return tsc;
91 }
92
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