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