diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/time/timekeeping.c | 42 |
1 files changed, 41 insertions, 1 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 4e18db1819f8..3096e10e0a1d 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1195,6 +1195,46 @@ static bool timestamp_in_interval(u64 start, u64 end, u64 ts) return false; } +static bool convert_clock(u64 *val, u32 numerator, u32 denominator) +{ + u64 rem, res; + + if (!numerator || !denominator) + return false; + + res = div64_u64_rem(*val, denominator, &rem) * numerator; + *val = res + div_u64(rem * numerator, denominator); + return true; +} + +static bool convert_base_to_cs(struct system_counterval_t *scv) +{ + struct clocksource *cs = tk_core.timekeeper.tkr_mono.clock; + struct clocksource_base *base; + u32 num, den; + + /* The timestamp was taken from the time keeper clock source */ + if (cs->id == scv->cs_id) + return true; + + /* + * Check whether cs_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 != scv->cs_id) + return false; + + num = scv->use_nsecs ? cs->freq_khz : base->numerator; + den = scv->use_nsecs ? USEC_PER_SEC : base->denominator; + + if (!convert_clock(&scv->cycles, num, den)) + return false; + + scv->cycles += base->offset; + return true; +} + /** * get_device_system_crosststamp - Synchronously capture system/device timestamp * @get_time_fn: Callback to get simultaneous device time and @@ -1241,7 +1281,7 @@ int get_device_system_crosststamp(int (*get_time_fn) * installed timekeeper clocksource */ if (system_counterval.cs_id == CSID_GENERIC || - tk->tkr_mono.clock->id != system_counterval.cs_id) + !convert_base_to_cs(&system_counterval)) return -ENODEV; cycles = system_counterval.cycles; |