67 lines
2.1 KiB
C
67 lines
2.1 KiB
C
/*
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* Copyright (c) 2016 Intel Corporation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <nanokernel.h>
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#include <kernel_structs.h>
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/**
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*
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* @brief Power save idle routine
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*
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* This function will be called by the nanokernel idle loop or possibly within
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* an implementation of _sys_power_save_idle in the microkernel when the
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* '_sys_power_save_flag' variable is non-zero.
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*
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* @return N/A
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*/
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void nano_cpu_idle(void)
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{
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/* Do nothing but unconditionally unlock interrupts and return to the
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* caller. This CPU does not have any kind of power saving instruction.
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*/
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irq_unlock(NIOS2_STATUS_PIE_MSK);
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}
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/**
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*
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* @brief Atomically re-enable interrupts and enter low power mode
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*
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* This function is utilized by the nanokernel object "wait" APIs for tasks,
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* e.g. nano_task_lifo_get(), nano_task_sem_take(),
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* nano_task_stack_pop(), and nano_task_fifo_get().
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*
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* INTERNAL
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* The requirements for nano_cpu_atomic_idle() are as follows:
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* 1) The enablement of interrupts and entering a low-power mode needs to be
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* atomic, i.e. there should be no period of time where interrupts are
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* enabled before the processor enters a low-power mode. See the comments
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* in nano_task_lifo_get(), for example, of the race condition that
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* occurs if this requirement is not met.
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*
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* 2) After waking up from the low-power mode, the interrupt lockout state
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* must be restored as indicated in the 'imask' input parameter.
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*
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* @return N/A
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*/
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void nano_cpu_atomic_idle(unsigned int key)
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{
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/* Do nothing but restore IRQ state. This CPU does not have any
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* kind of power saving instruction.
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*/
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irq_unlock(key);
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}
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