79 lines
2.4 KiB
C
79 lines
2.4 KiB
C
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/*
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* Copyright (c) 2020 Oticon A/S
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* Copyright (c) 2023 Nordic Semiconductor ASA
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <stdbool.h>
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#include <stdint.h>
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#include <zephyr/arch/posix/posix_soc_if.h>
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#include <posix_board_if.h>
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#include <posix_soc.h>
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#include "nsi_hw_scheduler.h"
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#include "nsi_timer_model.h"
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/**
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* Replacement to the kernel k_busy_wait()
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* Will block this thread (and therefore the whole Zephyr) during usec_to_wait
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*
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* Note that interrupts may be received in the meanwhile and that therefore this
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* thread may lose context.
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* Therefore the wait time may be considerably longer.
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*
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* All this function ensures is that it will return after usec_to_wait or later.
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*
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* This special arch_busy_wait() is necessary due to how the POSIX arch/SOC INF
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* models a CPU. Conceptually it could be thought as if the MCU was running
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* at an infinitely high clock, and therefore no simulated time passes while
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* executing instructions(*1).
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* Therefore to be able to busy wait this function does the equivalent of
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* programming a dedicated timer which will raise a non-maskable interrupt,
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* and halting the CPU.
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*
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* (*1) In reality simulated time is simply not advanced just due to the "MCU"
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* running. Meaning, the SW running on the MCU is assumed to take 0 time.
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*/
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void arch_busy_wait(uint32_t usec_to_wait)
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{
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uint64_t time_end = nsi_hws_get_time() + usec_to_wait;
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while (nsi_hws_get_time() < time_end) {
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/*
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* There may be wakes due to other interrupts including
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* other threads calling arch_busy_wait
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*/
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hwtimer_wake_in_time(time_end);
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posix_halt_cpu();
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}
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}
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/**
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* Will block this thread (and therefore the whole Zephyr) during usec_to_waste
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*
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* Very similar to arch_busy_wait(), but if an interrupt or context switch
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* occurs this function will continue waiting after, ensuring that
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* usec_to_waste are spent in this context, irrespectively of how much more
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* time would be spent on interrupt handling or possible switched-in tasks.
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*
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* Can be used to emulate code execution time.
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*/
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void posix_cpu_hold(uint32_t usec_to_waste)
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{
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uint64_t time_start;
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int64_t to_wait = usec_to_waste;
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while (to_wait > 0) {
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/*
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* There may be wakes due to other interrupts or nested calls to
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* cpu_hold in interrupt handlers
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*/
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time_start = nsi_hws_get_time();
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hwtimer_wake_in_time(time_start + to_wait);
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posix_change_cpu_state_and_wait(true);
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to_wait -= nsi_hws_get_time() - time_start;
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posix_irq_handler();
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}
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}
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