diff options
Diffstat (limited to 'arch/ia64/kernel/sys_ia64.c')
| -rw-r--r-- | arch/ia64/kernel/sys_ia64.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/arch/ia64/kernel/sys_ia64.c b/arch/ia64/kernel/sys_ia64.c index e14db25146c2..215bf3f8cb20 100644 --- a/arch/ia64/kernel/sys_ia64.c +++ b/arch/ia64/kernel/sys_ia64.c @@ -166,3 +166,29 @@ ia64_mremap (unsigned long addr, unsigned long old_len, unsigned long new_len, u force_successful_syscall_return(); return addr; } + +asmlinkage long +ia64_clock_getres(const clockid_t which_clock, struct __kernel_timespec __user *tp) +{ + /* + * ia64's clock_gettime() syscall is implemented as a vdso call + * fsys_clock_gettime(). Currently it handles only + * CLOCK_REALTIME and CLOCK_MONOTONIC. Both are based on + * 'ar.itc' counter which gets incremented at a constant + * frequency. It's usually 400MHz, ~2.5x times slower than CPU + * clock frequency. Which is almost a 1ns hrtimer, but not quite. + * + * Let's special-case these timers to report correct precision + * based on ITC frequency and not HZ frequency for supported + * clocks. + */ + switch (which_clock) { + case CLOCK_REALTIME: + case CLOCK_MONOTONIC: + s64 tick_ns = DIV_ROUND_UP(NSEC_PER_SEC, local_cpu_data->itc_freq); + struct timespec64 rtn_tp = ns_to_timespec64(tick_ns); + return put_timespec64(&rtn_tp, tp); + } + + return sys_clock_getres(which_clock, tp); +} |