Add Critical Section HAL API specification

features/FEATURE_BLE/targets/TARGET_NORDIC/TARGET_MCU_NRF51822/hal_patch/critical_section_api.c

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+/*
+ * Copyright (c) 2015-2017, ARM Limited, All Rights Reserved
+ * 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.
+ */
+#include "cmsis.h"
+#include "nrf_error.h"
+#include "nrf_sdm.h"
+#include "nrf_soc.h"
+
+#include <stdbool.h>
+#include <stdint.h>
+
+static union {
+    uint32_t _PRIMASK_state;
+    uint8_t _sd_state;
+} _state = {0};
+
+static bool _use_softdevice_routine = false;
+static bool _state_saved = false;
+
+void hal_critical_section_enter(void)
+{
+    // Fetch the current state of interrupts
+    uint32_t primask = __get_PRIMASK();
+    uint8_t temp_state = 0;
+
+    // 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 softdevice can be used, use it.
+        sd_nvic_critical_region_enter(&temp_state);
+        _use_softdevice_routine = true;
+
+        if (_state_saved == false) {
+            _state._sd_state = temp_state;
+        }
+    } else {
+        // If interrupts are enabled, disable them.
+        if (primask == 0) {
+            __disable_irq();
+        }
+
+        // Store PRIMASK state, it will be restored when exiting critical
+        // section.
+        _use_softdevice_routine = false;
+
+        if (_state_saved == false) {
+            _state._PRIMASK_state = primask;
+        }
+    }
+
+    _state_saved = true;
+}
+
+void hal_critical_section_exit(void)
+{
+    _state_saved = false;
+
+    // Restore the state as it was prior to entering the critical section.
+    if (_use_softdevice_routine) {
+        sd_nvic_critical_region_exit(_state._sd_state)
+    } else {
+        __set_PRIMASK(_state._PRIMASK_state);
+    }
+}
+
+bool hal_in_critical_section(void)
+{
+    return (_state_saved == true);
+}

hal/critical_section_api.h

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+/** \addtogroup hal */
+/** @{*/
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2017 ARM Limited
+ *
+ * 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.
+ */
+#ifndef MBED_CRITICAL_SECTION_API_H
+#define MBED_CRITICAL_SECTION_API_H
+
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * \defgroup hal_critical Critical Section HAL functions
+ * @{
+ */
+
+/**
+ * Mark the start of a critical section
+ *
+ * This function will be called by core_util_critical_section_enter() each time
+ * the application requests to enter a critical section. The purpose of the
+ * critical section is to ensure mutual-exclusion synchronisation of the
+ * processor by preventing any change in processor control, the default
+ * behaviour requires storing the state of interrupts in the system before
+ * disabling them.
+ *
+ * The critical section code supports nesting. When a thread has entered a
+ * critical section it can make additional calls to
+ * core_util_critical_section_enter() without deadlocking itself. The critical
+ * section driver API tracks the number of nested calls to the critical section.
+ * The critical section will only be exited when
+ * core_util_critical_section_exit() has been called once for each time it
+ * entered the critical section.
+ *
+ * On the first call to enter a critical section this function MUST store the
+ * state of any interrupts or other application settings it will modify to
+ * facilitate the critical section.
+ *
+ * Each successive call to enter the critical section MUST ignore storing or
+ * modifying any application state.
+ *
+ * The default implementation of this function which will save the current state
+ * of interrupts before disabling them. This implementation can be found in
+ * mbed_critical_section_api.c. This behaviour is can be overridden on a per
+ * platform basis by providing a different implementation within the correct
+ * targets directory.
+ */
+void hal_critical_section_enter(void);
+
+
+/** Mark the end of a critical section.
+ *
+ * The purpose of this function is to restore any state that was modified upon
+ * entering the critical section, allowing other threads or interrupts to change
+ * the processor control.
+ *
+ * This function will be called once by core_util_critical_section_exit() per
+ * critical section on last call to exit. When called, the application MUST
+ * restore the saved interrupt/application state that was saved when entering
+ * the critical section.
+ *
+ * There is a default implementation of this function, it will restore the state
+ * of interrupts that were previously saved when hal_critical_section_enter was
+ * first called, this implementation can be found in
+ * mbed_critical_section_api.c. This behaviour is overridable by providing a
+ * different function implementation within the correct targets directory.
+ */
+void hal_critical_section_exit(void);
+
+
+/** Determine if the application is currently running in a critical section
+ *
+ * The purpose of this function is to inform the caller whether or not the
+ * application is running in a critical section. This is done by checking if
+ * the current interrupt state has been saved in the underlying implementation,
+ * this could also be done by checking the state of the interrupts at the time
+ * of calling.
+ *
+ *  @return  True if running in a critical section, false if not.
+ */
+bool hal_in_critical_section(void);
+
+
+/**@}*/
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // MBED_CRITICAL_SECTION_API_H
+
+/** @}*/

hal/mbed_critical_section_api.c

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+/* mbed Microcontroller Library
+ * Copyright (c) 2017 ARM Limited
+ *
+ * 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.
+ */
+#include "cmsis.h"
+#include "hal/critical_section_api.h"
+#include "platform/mbed_assert.h"
+#include "platform/mbed_toolchain.h"
+
+#include <stdbool.h>
+
+static volatile bool critical_interrupts_enabled = false;
+static volatile bool state_saved = false;
+
+static bool are_interrupts_enabled(void)
+{
+#if defined(__CORTEX_A9)
+    return ((__get_CPSR() & 0x80) == 0);
+#else
+    return ((__get_PRIMASK() & 0x1) == 0);
+#endif
+}
+
+
+MBED_WEAK void hal_critical_section_enter(void)
+{
+    const bool interrupt_state = are_interrupts_enabled();
+
+    __disable_irq();
+
+    if (state_saved == true) {
+        return;
+    }
+
+    critical_interrupts_enabled = interrupt_state;
+    state_saved = true;
+}
+
+MBED_WEAK void hal_critical_section_exit(void)
+{
+#ifndef FEATURE_UVISOR
+    // Interrupts must be disabled on invoking an exit from a critical section
+    MBED_ASSERT(!are_interrupts_enabled());
+#endif
+    state_saved = false;
+
+    // Restore the IRQs to their state prior to entering the critical section
+    if (critical_interrupts_enabled == true) {
+        __enable_irq();
+    }
+}
+
+MBED_WEAK bool hal_in_critical_section(void)
+{
+    return (state_saved == true);
+}