File content as of revision 0:276e7a263c35:

// ----------------------------------------------------------------------------
// Copyright 2015-2017 ARM Ltd.
//
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------------------------------------------------------

#ifdef TARGET_MCU_NRF51

#include <stdint.h>                  // uint32_t, UINT32_MAX
#include <stddef.h>                  // NULL
#include <cmsis-core/core_generic.h> //__disable_irq, __enable_irq
#include <assert.h>
#include <stdbool.h>
#include <nrf_soc.h>
#include <nrf_sdm.h>

// Module include
#include "aq_critical.h"

static volatile union {
    uint32_t _PRIMASK_state;
    uint8_t  _sd_state;
} _state = { 0 } ;
static volatile uint32_t _entry_count = 0;
static volatile bool _use_softdevice_routine = false;

void aq_critical_section_enter()
{
    // if a critical section has already been entered, just update the counter
    if (_entry_count) {
        ++_entry_count;
        return;
    }

    // in this path, a critical section has never been entered
    uint32_t primask = __get_PRIMASK();

    // if interrupts are enabled, try to use the soft device
    uint8_t sd_enabled;
    if ((primask == 0) && (sd_softdevice_is_enabled(&sd_enabled) == NRF_SUCCESS) && sd_enabled == 1) {
        // if the soft device can be use, use it
        sd_nvic_critical_region_enter(&_state._sd_state);
        _use_softdevice_routine = true;
    } else {
        // if interrupts where enabled, disable them
        if(primask == 0) {
            __disable_irq();
        }

        // store the PRIMASK state, it will be restored at the end of the critical section
        _state._PRIMASK_state = primask;
        _use_softdevice_routine = false;
    }

    assert(_entry_count == 0); // entry count should always be equal to 0 at this point
    ++_entry_count;
}

void aq_critical_section_exit()
{
    assert(_entry_count > 0);
    --_entry_count;

    // If their is other segments which have entered the critical section, just leave
    if (_entry_count) {
        return;
    }

    // This is the last segment of the critical section, state should be restored as before entering
    // the critical section
    if (_use_softdevice_routine) {
        sd_nvic_critical_region_exit(_state._sd_state);
    } else {
        __set_PRIMASK(_state._PRIMASK_state);
    }
}

#endif //TARGET_MCU_NRF51