diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h index b2ee182d891e..fc12a9ba2c88 100644 --- a/include/linux/timekeeping.h +++ b/include/linux/timekeeping.h @@ -318,6 +318,10 @@ struct system_counterval_t { bool use_nsecs; }; +extern bool ktime_real_to_base_clock(ktime_t treal, + enum clocksource_ids base_id, u64 *cycles); +extern bool timekeeping_clocksource_has_base(enum clocksource_ids id); + /* * Get cross timestamp between system clock and device clock */ diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 3096e10e0a1d..da984a368a95 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1235,6 +1235,68 @@ static bool convert_base_to_cs(struct system_counterval_t *scv) return true; } +static bool convert_cs_to_base(u64 *cycles, enum clocksource_ids base_id) +{ + struct clocksource *cs = tk_core.timekeeper.tkr_mono.clock; + struct clocksource_base *base; + + /* + * Check whether base_id matches the base clock. Prevent the compiler from + * re-evaluating @base as the clocksource might change concurrently. + */ + base = READ_ONCE(cs->base); + if (!base || base->id != base_id) + return false; + + *cycles -= base->offset; + if (!convert_clock(cycles, base->denominator, base->numerator)) + return false; + return true; +} + +static bool convert_ns_to_cs(u64 *delta) +{ + struct tk_read_base *tkr = &tk_core.timekeeper.tkr_mono; + + if (BITS_TO_BYTES(fls64(*delta) + tkr->shift) >= sizeof(*delta)) + return false; + + *delta = div_u64((*delta << tkr->shift) - tkr->xtime_nsec, tkr->mult); + return true; +} + +/** + * ktime_real_to_base_clock() - Convert CLOCK_REALTIME timestamp to a base clock timestamp + * @treal: CLOCK_REALTIME timestamp to convert + * @base_id: base clocksource id + * @cycles: pointer to store the converted base clock timestamp + * + * Converts a supplied, future realtime clock value to the corresponding base clock value. + * + * Return: true if the conversion is successful, false otherwise. + */ +bool ktime_real_to_base_clock(ktime_t treal, enum clocksource_ids base_id, u64 *cycles) +{ + struct timekeeper *tk = &tk_core.timekeeper; + unsigned int seq; + u64 delta; + + do { + seq = read_seqcount_begin(&tk_core.seq); + if ((u64)treal < tk->tkr_mono.base_real) + return false; + delta = (u64)treal - tk->tkr_mono.base_real; + if (!convert_ns_to_cs(&delta)) + return false; + *cycles = tk->tkr_mono.cycle_last + delta; + if (!convert_cs_to_base(cycles, base_id)) + return false; + } while (read_seqcount_retry(&tk_core.seq, seq)); + + return true; +} +EXPORT_SYMBOL_GPL(ktime_real_to_base_clock); + /** * get_device_system_crosststamp - Synchronously capture system/device timestamp * @get_time_fn: Callback to get simultaneous device time and @@ -1346,6 +1408,30 @@ int get_device_system_crosststamp(int (*get_time_fn) } EXPORT_SYMBOL_GPL(get_device_system_crosststamp); +/** + * timekeeping_clocksource_has_base - Check whether the current clocksource + * is based on given a base clock + * @id: base clocksource ID + * + * Note: The return value is a snapshot which can become invalid right + * after the function returns. + * + * Return: true if the timekeeper clocksource has a base clock with @id, + * false otherwise + */ +bool timekeeping_clocksource_has_base(enum clocksource_ids id) +{ + /* + * This is a snapshot, so no point in using the sequence + * count. Just prevent the compiler from re-evaluating @base as the + * clocksource might change concurrently. + */ + struct clocksource_base *base = READ_ONCE(tk_core.timekeeper.tkr_mono.clock->base); + + return base ? base->id == id : false; +} +EXPORT_SYMBOL_GPL(timekeeping_clocksource_has_base); + /** * do_settimeofday64 - Sets the time of day. * @ts: pointer to the timespec64 variable containing the new time