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base-hw imx epit-timer: improve code readability

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Improves the readability of the implementation of the Timer::_duration method.

Ref #4959
This commit is contained in:
Martin Stein 2023-07-06 21:01:39 +02:00 committed by Norman Feske
parent 5ca6dd10f8
commit ca1a94d74c
1 changed files with 19 additions and 4 deletions
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23
repos/base-hw/src/core/spec/arm/imx_epit.cc
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@ -94,8 +94,23 @@ time_t Timer::_max_value() const {
time_t Timer::_duration() const
{
using Device = Board::Timer;
Device::Cnt::access_t const last = (Device::Cnt::access_t) _last_timeout_duration;
Device::Cnt::access_t const cnt = _device.read<Device::Cnt>();
return (_device.read<Device::Sr::Ocif>()) ? _max_value() - _device.read<Device::Cnt>() + last
: last - cnt;
Device::Cnt::access_t const initial_cnt {
(Device::Cnt::access_t)_last_timeout_duration };
/*
* There are two situations here:
*
* 1. SR.OCIF reads as 1, meaning, the timer IRQ has triggered. In
* this case we read CNT after having read SR.OCIF in order to
* ensure that we use a post-IRQ (wrapped) counter value.
*
* 2. SR.OCIF reads as 0, meaning, the timer IRQ hasn't triggered yet. In
* this case we read CNT before having read SR.OCIF in order to
* ensure that we use a pre-IRQ (non-wrapped) counter value.
*/
Device::Cnt::access_t const curr_cnt { _device.read<Device::Cnt>() };
if (_device.read<Device::Sr::Ocif>())
return _max_value() - _device.read<Device::Cnt>() + initial_cnt;
else
return initial_cnt - curr_cnt;
}