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"); 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"); 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