mirror of https://github.com/FOME-Tech/fome-fw.git
42 lines
1.3 KiB
C++
42 lines
1.3 KiB
C++
/**
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* @file efilib2.cpp
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*
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* @date Apr 14, 2014
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* @author Andrey Belomutskiy, (c) 2012-2014
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*/
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#include "efilib2.h"
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/**
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* The main use-case of this class is to keep track of a 64-bit global number of CPU ticks from reset.
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*
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* stm32f4 hardware has a 32-bit Cycle Count Register (CYCCNT), which is incremented with every CPU cycle.
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* With 32 bits and 168MHz speed this counter overflows every 4B/168M = 23 seconds. The job of this class is to
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* keep track of the current CYCCNT value, detect these overflows, and provide a nice,
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* clean 64 bit global cycle counter.
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*
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* In order for this to function, it's your responsibility to invoke offer() method at least once a second.
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*/
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Overflow64Counter::Overflow64Counter() {
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currentBase = 0;
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currentValue = 0;
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}
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uint64_t Overflow64Counter::get(uint32_t value, int isPrimaryThread) {
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// this method is lock-free, only one thread is allowed to commit state
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// these are local copies for thread-safery
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// todo: this is still not atomic, so technically not thread safe.
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uint32_t localValue = currentValue;
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uint64_t localBase = currentBase;
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if (value < localValue) {
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// new value less than previous value means there was an overflow in that 32 bit counter
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localBase += 0x100000000LL;
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}
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if (isPrimaryThread) {
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currentValue = value;
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currentBase = localBase;
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}
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return localBase + value;
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}
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