120 lines
3.3 KiB
C
120 lines
3.3 KiB
C
/**
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* \file
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* <!--
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* This file is part of BeRTOS.
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*
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* Bertos is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* As a special exception, you may use this file as part of a free software
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* library without restriction. Specifically, if other files instantiate
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* templates or use macros or inline functions from this file, or you compile
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* this file and link it with other files to produce an executable, this
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* file does not by itself cause the resulting executable to be covered by
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* the GNU General Public License. This exception does not however
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* invalidate any other reasons why the executable file might be covered by
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* the GNU General Public License.
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*
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* Copyright 2008 Bernie Innocenti <bernie@codewiz.org>
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* -->
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*
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* \brief CPU power management functions
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*
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* \author Bernie Innocenti <bernie@codewiz.org>
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*/
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#ifndef CPU_POWER_H
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#define CPU_POWER_H
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#include "cfg/cfg_proc.h"
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#include "cfg/cfg_wdt.h"
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#include <cfg/compiler.h>
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#if CONFIG_KERN
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#include <kern/proc.h>
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#endif
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#if CONFIG_WATCHDOG
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#include <drv/wdt.h>
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#endif
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/**
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* Let the CPU rest in tight busy loops
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*
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* User code that sits in a busy loop should call cpu_relax() every
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* once in a while to perform system-dependent idle processing.
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*
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* Depending on the system configuration, this might perform different
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* actions:
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*
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* - yield the CPU to other processes
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* - reset the watchdog timer to avoid it from triggering
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* - scale the CPU speed down to save power (unimplemented)
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* - let the event loop of the emulator process a few events
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*
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* \see proc_yield() cpu_pause()
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*/
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INLINE void cpu_relax(void)
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{
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MEMORY_BARRIER;
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#if CONFIG_KERN
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if (proc_preemptAllowed())
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proc_yield();
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#endif
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#if CONFIG_WATCHDOG
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wdt_reset();
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#endif
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}
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/**
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* Stop the processor until the next interrupt occurs.
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*
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* Pausing the CPU effectively reduces power usage, and should be used
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* whenever the program is idle waiting for the next event to occur.
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*
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* To avoid deadlocking, the caller should normally check for the
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* desired condition with interrupts disabled, and enter this function
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* while interrupts are still disabled:
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*
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* \code
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* IRQ_DISABLE();
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* while (!event_occurred)
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* cpu_pause();
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* IRQ_ENABLE();
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* \endcode
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*
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* \note Some implementations of cpu_pause() may return before any interrupt
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* has occurred. Calling code should take this possibility into account.
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*
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* \note This function is currently unimplemented
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*
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* \see cpu_relax() cpu_yield()
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*/
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INLINE void cpu_pause(void)
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{
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//ASSERT_IRQ_DISABLED();
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//IRQ_ENABLE();
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cpu_relax();
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//IRQ_DISABLE();
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}
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/**
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* Safely call cpu_pause() until the COND predicate becomes true.
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*/
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#define CPU_PAUSE_ON(COND) ATOMIC(while (!(COND)) { cpu_pause(); })
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#endif /* CPU_POWER_H */
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