armv8 - fix os_cpu_clock_frequency for armv8

System timer of ARMv8 runs at a different frequency than the CPU's.
The frequency is fixed, typically in the range 1-50MHz.  It can be
read at CNTFRQ special register.

Change-Id: I6a21a6a9e2df783559df0caec63d5525c2258227
Signed-off-by: Gabriel Ganne <gabriel.ganne@enea.com>

diff --git a/src/vppinfra/time.c b/src/vppinfra/time.c
index 2bdb9da..168d737 100644 (file)
--- a/src/vppinfra/time.c
+++ b/src/vppinfra/time.c
@@ -147,6 +147,12 @@ os_cpu_clock_frequency (void)
   if (clib_cpu_supports_invariant_tsc ())
     return estimate_clock_frequency (1e-3);
 
+#if defined (__aarch64__)
+  u64 tsc;
+  asm volatile ("mrs %0, CNTFRQ_EL0":"=r" (tsc));
+  return (f64) tsc;
+#endif
+
   /* First try /sys version. */
   cpu_freq = clock_frequency_from_sys_filesystem ();
   if (cpu_freq != 0)