src/soc/amd/stoneyridge/monotonic_timer.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <cpu/x86/msr.h>
   4 #include <timer.h>
   5 #include <timestamp.h>
   6
   7 #define CU_PTSC_MSR     0xc0010280
   8 #define PTSC_FREQ_MHZ   100
   9
  10 void timer_monotonic_get(struct mono_time *mt)
  11 {
  12         mono_time_set_usecs(mt, timestamp_get());
  13 }
  14
  15 /* The TSC has a non-constant rate before the microcode update is applied, so it can't be used
  16    in timestamp_get before that. Instead, the Performance Time Stamp Counter is used. */
  17 uint64_t timestamp_get(void)
  18 {
  19         msr_t msr;
  20
  21         msr = rdmsr(CU_PTSC_MSR);
  22
  23         return msr.raw / PTSC_FREQ_MHZ;
  24 }