Diff: platform/source/SysTimer.h

Revision:

1:9db0e321a9f4

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/platform/source/SysTimer.h	Tue Dec 31 06:02:27 2019 +0000
@@ -0,0 +1,243 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2019 ARM Limited
+ * 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.
+ */
+#ifndef MBED_SYS_TIMER_H
+#define MBED_SYS_TIMER_H
+
+#include "platform/NonCopyable.h"
+#include "platform/mbed_atomic.h"
+#include "drivers/TimerEvent.h"
+#include "cmsis.h"
+
+extern "C" {
+#if defined(TARGET_CORTEX_A)
+#include "irq_ctrl.h"
+#endif
+}
+
+namespace mbed {
+namespace internal {
+
+/**
+ * \defgroup mbed_SysTimer SysTimer class
+ * \ingroup platform-internal-api
+ * @{
+ */
+
+/**
+ * The SysTimer class is used to provide timing for system suspension, and
+ * the idle loop in TICKLESS mode.
+ *
+ * Template for speed for testing - only one instance will be used normally.
+ *
+ * @note SysTimer is not the part of Mbed API.
+ */
+template <uint32_t US_IN_TICK, bool IRQ = true>
+class SysTimer: private mbed::TimerEvent, private mbed::NonCopyable<SysTimer<US_IN_TICK, IRQ> > {
+public:
+
+    /**
+     * Default constructor uses LPTICKER if available (so the timer will
+     * continue to run in deep sleep), else USTICKER.
+     */
+    SysTimer();
+
+    SysTimer(const ticker_data_t *data);
+
+    virtual ~SysTimer();
+
+    /**
+     * Get the interrupt number for the tick
+     *
+     * @return interrupt number
+     */
+#if TARGET_CORTEX_A
+    static IRQn_ID_t get_irq_number();
+#elif TARGET_CORTEX_M
+    static IRQn_Type get_irq_number();
+#endif
+
+    /**
+     * Set the wake time
+     *
+     * Schedules an interrupt to cause wake-up in time for the event. Interrupt
+     * may be arranged early to account for latency. If the time has already
+     * passed, no interrupt will be scheduled.
+     *
+     * This is called from outside a critical section, as it is known to be
+     * a slow operation.
+     *
+     * If the wake time is already set, this is a no-op. But that check is racy,
+     * which means wake_time_set() should be rechecked after taking a critical
+     * section.
+     *
+     * As a side-effect, this clears the unacknowledged tick count - the caller
+     * is expected to use update_and_get_tick() after the suspend operation.
+     *
+     * @param at Wake up tick
+     * @warning If the ticker tick is already scheduled it needs to be cancelled first!
+     */
+    void set_wake_time(uint64_t at);
+
+    /**
+     * Check whether the wake time has passed
+     *
+     * This is a fast operation, based on checking whether the wake interrupt
+     * has run.
+     *
+     * @return true if the specified wake tick has passed
+     */
+    bool wake_time_passed() const
+    {
+        return core_util_atomic_load_bool(&_wake_time_passed);
+    }
+
+    /**
+     * Check whether wake timer is active
+     *
+     * @return true if the wake timer is active.
+     */
+    bool wake_time_set() const
+    {
+        return core_util_atomic_load_bool(&_wake_time_set);
+    }
+
+    /**
+     * Cancel any pending wake
+     */
+    void cancel_wake();
+
+    /**
+     * Schedule an os tick to fire
+     *
+     * Ticks will be rescheduled automatically every tick until cancel_tick is called.
+     *
+     * A tick will be fired immediately if there are any unacknowledged ticks.
+     *
+     * @warning If a tick is already scheduled it needs to be cancelled first!
+     */
+    void start_tick();
+
+    /**
+     * Acknowledge an os tick
+     *
+     * This will queue another os tick immediately if the os is running slow
+     */
+    void acknowledge_tick();
+
+    /**
+     * Prevent any more scheduled ticks from triggering
+     *
+     * If called from OS tick context, there may be remaining unacknowledged ticks.
+     */
+    void cancel_tick();
+
+    /**
+     * Check whether ticker is active
+     *
+     * Each time the tick interrupt fires, it is automatically rescheduled,
+     * so this will remain true once the tick is started, except during
+     * processing.
+     *
+     * @return true if the ticker is active.
+     */
+    bool ticking() const
+    {
+        return core_util_atomic_load_bool(&_ticking);
+    }
+
+    /**
+     * Check unacknowledged ticks
+     *
+     * Returns the count of how many times the OS timer has been queued minus
+     * the number of times is has been acknowledged.
+     *
+     * get_tick() - unacknowledged_ticks() should equal the OS's tick count,
+     * although such a calculation is not atomic if the ticker is currently running.
+     *
+     * @return number of unacknowledged ticks
+     */
+    int unacknowledged_ticks() const
+    {
+        return core_util_atomic_load_u8(&_unacknowledged_ticks);
+    }
+
+    /** Get the current tick count
+     *
+     * This count is updated by the ticker interrupt, if the ticker interrupt
+     * is running. It the ticker interrupt is not running, update_and_get_tick()
+     * should be used instead.
+     *
+     * This indicates how many ticks have been generated by the tick interrupt.
+     * The os_timer should equal this number minus the number of unacknowledged ticks.
+     *
+     * @return The number of ticks since timer creation.
+     */
+    uint64_t get_tick() const;
+
+    /** Update and get the current tick count
+     *
+     * This is a slow operation that reads the timer and adjusts for elapsed time.
+     * Can only be used when the ticker is not running, as there is no IRQ
+     * synchronization.
+     *
+     * This clears the unacknowledged tick counter - the caller is assumed to update
+     * their timer based on this return.
+     *
+     * @return The number of ticks since timer creation.
+     */
+    uint64_t update_and_get_tick();
+
+    /**
+     * Returns time since last tick
+     *
+     * @return Relative time in microseconds
+     */
+    us_timestamp_t get_time_since_tick() const;
+
+    /**
+     * Get the time
+     *
+     * Returns the instantaneous precision time from underlying timer.
+     * This is a slow operation so should not be called from critical sections.
+     *
+     * @return Current time in microseconds
+     */
+    us_timestamp_t get_time() const;
+
+protected:
+    virtual void handler();
+    void _increment_tick();
+    void _schedule_tick();
+    uint64_t _elapsed_ticks() const;
+    static void _set_irq_pending();
+    static void _clear_irq_pending();
+    us_timestamp_t _time_us;
+    uint64_t _tick;
+    uint8_t _unacknowledged_ticks;
+    bool _wake_time_set;
+    bool _wake_time_passed;
+    bool _wake_early;
+    bool _ticking;
+    bool _deep_sleep_locked;
+};
+
+/** @} */
+
+}
+}
+
+#endif