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9e566370bf
The inline assembly implementation was badly in need of improvement.
- irq_disable() took 2 CPU cycles more than needed
- The current interrupt state was stored in a temporary register and
afterwards copied to the target register, rather than storing it in the
target register right away
- The lower bits of the state were cleared (as they have no meaning for the
interrupt status), but the API purposely never required such things from
implementations.
- irq_restore() took 5 CPU cycles. This was reduced to 3 CPU cycles (or 2 CPU
cycles in the best case)
111 lines
2.5 KiB
C
111 lines
2.5 KiB
C
/*
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* Copyright (C) 2014 Freie Universität Berlin, Hinnerk van Bruinehsen
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* 2018 RWTH Aachen, Josua Arndt <jarndt@ias.rwth-aachen.de>
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* 2020 Otto-von-Guericke-Universität Magdeburg
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup cpu_atmega_common
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* @{
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*
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* @file
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* @brief Implementation of the kernels irq interface
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*
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* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
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* @author Hinnerk van Bruinehsen <h.v.bruinehsen@fu-berlin.de>
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* @author Josua Arndt <jarndt@ias.rwth-aachen.de>
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* @author Marian Buschsieweke <marian.buschsieweke@ovgu.de>
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*
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*/
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#ifndef IRQ_ARCH_H
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#define IRQ_ARCH_H
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#include <stdint.h>
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#include <stdio.h>
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#include <stdint.h>
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#include "irq.h"
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#include "cpu.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief Disable all maskable interrupts
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*/
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__attribute__((always_inline)) static inline unsigned int irq_disable(void)
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{
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uint8_t mask;
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__asm__ volatile(
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"in %[dest], __SREG__" "\n\t"
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"cli" "\n\t"
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: [dest] "=r"(mask)
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: /* no inputs */
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: "memory"
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);
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return mask;
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}
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/**
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* @brief Enable all maskable interrupts
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*/
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__attribute__((always_inline)) static inline unsigned int irq_enable(void)
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{
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uint8_t mask;
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__asm__ volatile(
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"in %[dest], __SREG__" "\n\t"
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"sei" "\n\t"
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: [dest] "=r"(mask)
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: /* no inputs */
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: "memory"
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);
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return mask;
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}
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/**
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* @brief Restore the state of the IRQ flags
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*/
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__attribute__((always_inline)) static inline void irq_restore(unsigned int _state)
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{
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uint8_t state = (uint8_t)_state;
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/*
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* Implementation in pseudo-code:
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*
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* disable_irqs();
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* if (state & BIT7) {
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* enable_irqs();
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* }
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*
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* This takes 3 CPU Cycles if BIT7 is set (IRQs are enabled), otherwise 2.
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*/
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__asm__ volatile(
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"cli" "\n\t"
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"sbrc %[state], 7" "\n\t"
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"sei" "\n\t"
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: /* no outputs */
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: [state] "r"(state)
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: "memory"
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);
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}
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/**
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* @brief See if the current context is inside an ISR
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*/
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__attribute__((always_inline)) static inline int irq_is_in(void)
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{
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uint8_t state = atmega_get_state();
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return (state & ATMEGA_STATE_FLAG_ISR);
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}
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#ifdef __cplusplus
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}
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#endif
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/** @} */
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#endif /* IRQ_ARCH_H */
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