VILLASnode/common/lib/tsc.cpp

/* Measure time and sleep with IA-32 time-stamp counter.
 *
 * Author: Steffen Vogel <post@steffenvogel.de>
 * SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
 * SPDX-License-Identifier: Apache-2.0
 */

#include <villas/kernel/kernel.hpp>
#include <villas/tsc.hpp>

using namespace villas;

int tsc_init(struct Tsc *t) {
#if defined(__x86_64__) || defined(__i386__)
  uint32_t eax = 0, ebx = 0, ecx = 0, edx = 0;

  // Check if TSC is supported
  __get_cpuid(0x1, &eax, &ebx, &ecx, &edx);
  if (!(edx & bit_TSC))
    return -2;

  // Check if RDTSCP instruction is supported
  __get_cpuid(0x80000001, &eax, &ebx, &ecx, &edx);
  t->rdtscp_supported = edx & bit_RDTSCP;

  // Check if TSC is invariant
  __get_cpuid(0x80000007, &eax, &ebx, &ecx, &edx);
  t->is_invariant = edx & bit_TSC_INVARIANT;

  // Intel SDM Vol 3, Section 18.7.3:
  // Nominal TSC frequency = CPUID.15H.ECX[31:0] * CPUID.15H.EBX[31:0] ) ÷ CPUID.15H.EAX[31:0]
  __get_cpuid(0x15, &eax, &ebx, &ecx, &edx);

  if (ecx != 0)
    t->frequency = ecx * ebx / eax;
  else {
#ifdef __linux__
    int ret = kernel::get_cpu_frequency(&t->frequency);
    if (ret)
      return ret;
#endif
  }
#else
#ifdef __linux__
  int ret = kernel::get_cpu_frequency(&t->frequency);
  if (ret)
    return ret;
#endif
#endif
  if (t->frequency)
    return 0; // Frequency determined with success
  else
    return -1;
}

uint64_t tsc_rate_to_cycles(struct Tsc *t, double rate) {
  return t->frequency / rate;
}