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timekeeping: Fix cross-timestamp interpolation for non-x86
[ Upstream commit14274d0bd3
] So far, get_device_system_crosststamp() unconditionally passes system_counterval.cycles to timekeeping_cycles_to_ns(). But when interpolating system time (do_interp == true), system_counterval.cycles is before tkr_mono.cycle_last, contrary to the timekeeping_cycles_to_ns() expectations. On x86, CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE will mitigate on interpolating, setting delta to 0. With delta == 0, xtstamp->sys_monoraw and xtstamp->sys_realtime are then set to the last update time, as implicitly expected by adjust_historical_crosststamp(). On other architectures, the resulting nonsense xtstamp->sys_monoraw and xtstamp->sys_realtime corrupt the xtstamp (ts) adjustment in adjust_historical_crosststamp(). Fix this by deriving xtstamp->sys_monoraw and xtstamp->sys_realtime from the last update time when interpolating, by using the local variable "cycles". The local variable already has the right value when interpolating, unlike system_counterval.cycles. Fixes:2c756feb18
("time: Add history to cross timestamp interface supporting slower devices") Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: John Stultz <jstultz@google.com> Link: https://lore.kernel.org/r/20231218073849.35294-4-peter.hilber@opensynergy.com Signed-off-by: Sasha Levin <sashal@kernel.org>
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1 changed files with 2 additions and 4 deletions
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@ -1244,10 +1244,8 @@ int get_device_system_crosststamp(int (*get_time_fn)
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tk_core.timekeeper.offs_real);
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base_raw = tk->tkr_raw.base;
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nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono,
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system_counterval.cycles);
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nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw,
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system_counterval.cycles);
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nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, cycles);
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nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw, cycles);
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} while (read_seqcount_retry(&tk_core.seq, seq));
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xtstamp->sys_realtime = ktime_add_ns(base_real, nsec_real);
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