Add sub-ms resolution for time.monotonic_ns, on samd and nrf ports #2342
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Assuming the samd code is right, this fixes a rare problem where a timeout would be ~1ms too short; the problem could also be observed with the monotonic_ns code which could incorrectly jump forward 1ms.
.. which, on some ports, can return sub-millisecond precision thanks to how SysTick works.
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I think this is ready for review. |
dhalbert
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Dec 2, 2019
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| uint64_t time64 = common_hal_time_monotonic_ns(); | ||
| return mp_obj_new_int_from_ll((long long) time64); |
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Why is STM32 different than the others? Maybe it should also share the same code?
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I started doing a more extensive re-factor but it kinda got out of control. I feel like background and tick could both have a lot more commonality than they have, especially on systems which directly use ARM SysTick. I'd be content closing this unmerged now and returning to it in 6.0 -- nobody's assigned this a 5-ish milestone. Thoughts? @tannewt @dhalbert |
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I'm impartial. Either way is fine with me. |
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We want to redo timekeeping anyway to be able to sleep, so ok by me to wait. |
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This also addresses a problem where current_tick() / wait_until() could be wrong by 1ms on nRF, by copying systick code from the samd port.
Testing performed: on pyportal and cpb, looked at
time.monotonic_nsvalues. The values always went forward, and usually by "consistent" amounts in a small loop:On samd builds, this new code isn't enabled for small builds to avoid increasing code size. So those boards will still have just 1ms resolution in monotonic_ns. Also, the resolution of time.monotonic isn't increased, since very soon after boot even 1ms resolution is not possible in CP floating-point values.