diff options
Diffstat (limited to 'arch/x86/kernel/tsc.c')
| -rw-r--r-- | arch/x86/kernel/tsc.c | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index fb4302738410..ef32297ff17e 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1179,6 +1179,45 @@ struct system_counterval_t convert_art_to_tsc(u64 art) } EXPORT_SYMBOL(convert_art_to_tsc); +/** + * convert_art_ns_to_tsc() - Convert ART in nanoseconds to TSC. + * @art_ns: ART (Always Running Timer) in unit of nanoseconds + * + * PTM requires all timestamps to be in units of nanoseconds. When user + * software requests a cross-timestamp, this function converts system timestamp + * to TSC. + * + * This is valid when CPU feature flag X86_FEATURE_TSC_KNOWN_FREQ is set + * indicating the tsc_khz is derived from CPUID[15H]. Drivers should check + * that this flag is set before conversion to TSC is attempted. + * + * Return: + * struct system_counterval_t - system counter value with the pointer to the + * corresponding clocksource + * @cycles: System counter value + * @cs: Clocksource corresponding to system counter value. Used + * by timekeeping code to verify comparibility of two cycle + * values. + */ + +struct system_counterval_t convert_art_ns_to_tsc(u64 art_ns) +{ + u64 tmp, res, rem; + + rem = do_div(art_ns, USEC_PER_SEC); + + res = art_ns * tsc_khz; + tmp = rem * tsc_khz; + + do_div(tmp, USEC_PER_SEC); + res += tmp; + + return (struct system_counterval_t) { .cs = art_related_clocksource, + .cycles = res}; +} +EXPORT_SYMBOL(convert_art_ns_to_tsc); + + static void tsc_refine_calibration_work(struct work_struct *work); static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work); /** |