tools/perf/arch/arm64/util/tsc.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/types.h>
   4
   5 #include "../../../util/tsc.h"
   6
   7 u64 rdtsc(void)
   8 {
   9         u64 val;
  10
  11         /*
  12          * According to ARM DDI 0487F.c, from Armv8.0 to Armv8.5 inclusive, the
  13          * system counter is at least 56 bits wide; from Armv8.6, the counter
  14          * must be 64 bits wide.  So the system counter could be less than 64
  15          * bits wide and it is attributed with the flag 'cap_user_time_short'
  16          * is true.
  17          */
  18         asm volatile("mrs %0, cntvct_el0" : "=r" (val));
  19
  20         return val;
  21 }