src/arch/ppc64/arch_timer.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <timer.h>
   4 #include <delay.h>
   5 #include <cpu/power/spr.h>
   6
   7 /* Refer to hostboot/src/kernel/timemgr.C */
   8
   9 /* Time base frequency is 512 MHz so 512 ticks per usec */
  10 #define TB_TICKS_PER_USEC 512
  11
  12 __weak void init_timer(void) { /* do nothing */ }
  13
  14 static struct monotonic_counter {
  15         int initialized;
  16         struct mono_time time;
  17         uint64_t last_value;
  18 } mono_counter;
  19
  20 void timer_monotonic_get(struct mono_time *mt)
  21 {
  22         uint64_t current_tick;
  23         uint64_t usecs_elapsed;
  24
  25         if (!mono_counter.initialized) {
  26                 mono_counter.last_value = read_spr(SPR_TB);
  27                 mono_counter.initialized = 1;
  28         }
  29
  30         current_tick = read_spr(SPR_TB);
  31         usecs_elapsed = (current_tick - mono_counter.last_value) / TB_TICKS_PER_USEC;
  32
  33         /* Update current time and tick values only if a full tick occurred. */
  34         if (usecs_elapsed) {
  35                 mono_time_add_usecs(&mono_counter.time, usecs_elapsed);
  36                 mono_counter.last_value = current_tick;
  37         }
  38
  39         /* Save result. */
  40         *mt = mono_counter.time;
  41 }