Diff: targets/TARGET_NORDIC/TARGET_NRF5/us_ticker.c

Revision:

149:156823d33999

Child:

150:02e0a0aed4ec

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_NORDIC/TARGET_NRF5/us_ticker.c	Fri Oct 28 11:17:30 2016 +0100
@@ -0,0 +1,562 @@
+/*
+ * Copyright (c) 2013 Nordic Semiconductor ASA
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ *   1. Redistributions of source code must retain the above copyright notice, this list
+ *      of conditions and the following disclaimer.
+ *
+ *   2. Redistributions in binary form, except as embedded into a Nordic Semiconductor ASA
+ *      integrated circuit in a product or a software update for such product, must reproduce
+ *      the above copyright notice, this list of conditions and the following disclaimer in
+ *      the documentation and/or other materials provided with the distribution.
+ *
+ *   3. Neither the name of Nordic Semiconductor ASA nor the names of its contributors may be
+ *      used to endorse or promote products derived from this software without specific prior
+ *      written permission.
+ *
+ *   4. This software, with or without modification, must only be used with a
+ *      Nordic Semiconductor ASA integrated circuit.
+ *
+ *   5. Any software provided in binary or object form under this license must not be reverse
+ *      engineered, decompiled, modified and/or disassembled.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "us_ticker_api.h"
+#include "common_rtc.h"
+#include "app_util.h"
+#include "nrf_drv_common.h"
+#include "lp_ticker_api.h"
+
+
+//------------------------------------------------------------------------------
+// Common stuff used also by lp_ticker and rtc_api (see "common_rtc.h").
+//
+#include "app_util_platform.h"
+
+bool              m_common_rtc_enabled = false;
+uint32_t volatile m_common_rtc_overflows = 0;
+
+#if defined(TARGET_MCU_NRF51822)
+void common_rtc_irq_handler(void)
+#else
+void COMMON_RTC_IRQ_HANDLER(void)
+#endif
+{
+    if (nrf_rtc_event_pending(COMMON_RTC_INSTANCE, US_TICKER_EVENT)) {
+        us_ticker_irq_handler();
+    }
+
+#if DEVICE_LOWPOWERTIMER
+    if (nrf_rtc_event_pending(COMMON_RTC_INSTANCE, LP_TICKER_EVENT)) {
+
+        lp_ticker_irq_handler();
+    }
+#endif
+
+    if (nrf_rtc_event_pending(COMMON_RTC_INSTANCE, NRF_RTC_EVENT_OVERFLOW)) {
+        nrf_rtc_event_clear(COMMON_RTC_INSTANCE, NRF_RTC_EVENT_OVERFLOW);
+        // Don't disable this event. It shall occur periodically.
+
+        ++m_common_rtc_overflows;
+    }
+}
+
+void common_rtc_init(void)
+{
+    if (m_common_rtc_enabled) {
+        return;
+    }
+
+    // RTC is driven by the low frequency (32.768 kHz) clock, a proper request
+    // must be made to have it running.
+    // Currently this clock is started in 'SystemInit' (see "system_nrf51.c"
+    // or "system_nrf52.c", respectively).
+
+    nrf_rtc_prescaler_set(COMMON_RTC_INSTANCE, 0);
+
+    nrf_rtc_event_clear(COMMON_RTC_INSTANCE, US_TICKER_EVENT);
+#if defined(TARGET_MCU_NRF51822)
+    nrf_rtc_event_clear(COMMON_RTC_INSTANCE, OS_TICK_EVENT);
+#endif
+#if DEVICE_LOWPOWERTIMER
+    nrf_rtc_event_clear(COMMON_RTC_INSTANCE, LP_TICKER_EVENT);
+#endif
+    nrf_rtc_event_clear(COMMON_RTC_INSTANCE, NRF_RTC_EVENT_OVERFLOW);
+
+    // Interrupts on all related events are enabled permanently. Particular
+    // events will be enabled or disabled as needed (such approach is more
+    // energy efficient).
+    nrf_rtc_int_enable(COMMON_RTC_INSTANCE,
+    #if defined(TARGET_MCU_NRF51822)
+        OS_TICK_INT_MASK |
+    #endif
+    #if DEVICE_LOWPOWERTIMER
+        LP_TICKER_INT_MASK |
+    #endif
+        US_TICKER_INT_MASK |
+        NRF_RTC_INT_OVERFLOW_MASK);
+
+    // This event is enabled permanently, since overflow indications are needed
+    // continuously.
+    nrf_rtc_event_enable(COMMON_RTC_INSTANCE, NRF_RTC_INT_OVERFLOW_MASK);
+    // All other relevant events are initially disabled.
+    nrf_rtc_event_disable(COMMON_RTC_INSTANCE,
+    #if defined(TARGET_MCU_NRF51822)
+        OS_TICK_INT_MASK |
+    #endif
+    #if DEVICE_LOWPOWERTIMER
+        LP_TICKER_INT_MASK |
+    #endif
+        US_TICKER_INT_MASK);
+
+    nrf_drv_common_irq_enable(nrf_drv_get_IRQn(COMMON_RTC_INSTANCE),
+        APP_IRQ_PRIORITY_LOW);
+
+    nrf_rtc_task_trigger(COMMON_RTC_INSTANCE, NRF_RTC_TASK_START);
+
+    m_common_rtc_enabled = true;
+}
+
+uint32_t common_rtc_32bit_ticks_get(void)
+{
+    uint32_t ticks = nrf_rtc_counter_get(COMMON_RTC_INSTANCE);
+    // The counter used for time measurements is less than 32 bit wide,
+    // so its value is complemented with the number of registered overflows
+    // of the counter.
+    ticks += (m_common_rtc_overflows << RTC_COUNTER_BITS);
+    return ticks;
+}
+
+uint64_t common_rtc_64bit_us_get(void)
+{
+    uint32_t ticks = common_rtc_32bit_ticks_get();
+    // [ticks -> microseconds]
+    return ROUNDED_DIV(((uint64_t)ticks) * 1000000, RTC_INPUT_FREQ);
+}
+
+void common_rtc_set_interrupt(uint32_t us_timestamp, uint32_t cc_channel,
+                              uint32_t int_mask)
+{
+    // The internal counter is clocked with a frequency that cannot be easily
+    // multiplied to 1 MHz, therefore besides the translation of values
+    // (microsecond <-> ticks) a special care of overflows handling must be
+    // taken. Here the 32-bit timestamp value is complemented with information
+    // about current the system up time of (ticks + number of overflows of tick
+    // counter on upper bits, converted to microseconds), and such 64-bit value
+    // is then translated to counter ticks. Finally, the lower 24 bits of thus
+    // calculated value is written to the counter compare register to prepare
+    // the interrupt generation.
+    uint64_t current_time64 = common_rtc_64bit_us_get();
+    // [add upper 32 bits from the current time to the timestamp value]
+    uint64_t timestamp64 = us_timestamp +
+        (current_time64 & ~(uint64_t)0xFFFFFFFF);
+    // [if the original timestamp value happens to be after the 32 bit counter
+    //  of microsends overflows, correct the upper 32 bits accordingly]
+    if (us_timestamp < (uint32_t)(current_time64 & 0xFFFFFFFF)) {
+        timestamp64 += ((uint64_t)1 << 32);
+    }
+    // [microseconds -> ticks, always round the result up to avoid too early
+    //  interrupt generation]
+    uint32_t compare_value =
+        (uint32_t)CEIL_DIV((timestamp64) * RTC_INPUT_FREQ, 1000000);
+
+    // The COMPARE event occurs when the value in compare register is N and
+    // the counter value changes from N-1 to N. Therefore, the minimal safe
+    // difference between the compare value to be set and the current counter
+    // value is 2 ticks. This guarantees that the compare trigger is properly
+    // setup before the compare condition occurs.
+    uint32_t closest_safe_compare = common_rtc_32bit_ticks_get() + 2;
+    if ((int)(compare_value - closest_safe_compare) <= 0) {
+        compare_value = closest_safe_compare;
+    }
+
+    nrf_rtc_cc_set(COMMON_RTC_INSTANCE, cc_channel, RTC_WRAP(compare_value));
+    nrf_rtc_event_enable(COMMON_RTC_INSTANCE, int_mask);
+}
+//------------------------------------------------------------------------------
+
+
+void us_ticker_init(void)
+{
+    common_rtc_init();
+}
+
+uint32_t us_ticker_read()
+{
+    us_ticker_init();
+    return (uint32_t)common_rtc_64bit_us_get();
+}
+
+void us_ticker_set_interrupt(timestamp_t timestamp)
+{
+    common_rtc_set_interrupt(timestamp,
+        US_TICKER_CC_CHANNEL, US_TICKER_INT_MASK);
+}
+
+void us_ticker_disable_interrupt(void)
+{
+    nrf_rtc_event_disable(COMMON_RTC_INSTANCE, US_TICKER_INT_MASK);
+}
+
+void us_ticker_clear_interrupt(void)
+{
+    nrf_rtc_event_clear(COMMON_RTC_INSTANCE, US_TICKER_EVENT);
+}
+
+
+// Since there is no SysTick on NRF51, the RTC1 channel 1 is used as an
+// alternative source of RTOS ticks.
+#if defined(TARGET_MCU_NRF51822)
+
+#include "toolchain.h"
+
+
+#define MAX_RTC_COUNTER_VAL     ((1uL << RTC_COUNTER_BITS) - 1)
+
+/**
+ * The value previously set in the capture compare register of channel 1
+ */
+static uint32_t previous_tick_cc_value = 0;
+
+/*
+ RTX provide the following definitions which are used by the tick code:
+   * os_trv: The number (minus 1) of clock cycle between two tick.
+   * os_clockrate: Time duration between two ticks (in us).
+   * OS_Tick_Handler: The function which handle a tick event.
+     This function is special because it never returns.
+ Those definitions are used by the code which handle the os tick.
+ To allow compilation of us_ticker programs without RTOS, those symbols are
+ exported from this module as weak ones.
+ */
+MBED_WEAK uint32_t const os_trv;
+MBED_WEAK uint32_t const os_clockrate;
+MBED_WEAK void OS_Tick_Handler() { }
+
+
+#if defined (__CC_ARM)         /* ARMCC Compiler */
+
+__asm void COMMON_RTC_IRQ_HANDLER(void)
+{
+    IMPORT  OS_Tick_Handler
+    IMPORT  common_rtc_irq_handler
+
+    /**
+     * Chanel 1 of RTC1 is used by RTX as a systick.
+     * If the compare event on channel 1 is set, then branch to OS_Tick_Handler.
+     * Otherwise, just execute common_rtc_irq_handler.
+     * This function has to be written in assembly and tagged as naked because OS_Tick_Handler
+     * will never return.
+     * A c function would put lr on the stack before calling OS_Tick_Handler and this value
+     * would never been dequeued.
+     *
+     * \code
+     * void COMMON_RTC_IRQ_HANDLER(void) {
+         if(NRF_RTC1->EVENTS_COMPARE[1]) {
+             // never return...
+             OS_Tick_Handler();
+         } else {
+             common_rtc_irq_handler();
+         }
+       }
+     * \endcode
+     */
+    ldr r0,=0x40011144
+    ldr r1, [r0, #0]
+    cmp r1, #0
+    beq US_TICKER_HANDLER
+    bl OS_Tick_Handler
+US_TICKER_HANDLER
+    push {r3, lr}
+    bl common_rtc_irq_handler
+    pop {r3, pc}
+    ; ALIGN ;
+}
+
+#elif defined (__GNUC__)        /* GNU Compiler */
+
+__attribute__((naked)) void COMMON_RTC_IRQ_HANDLER(void)
+{
+    /**
+     * Chanel 1 of RTC1 is used by RTX as a systick.
+     * If the compare event on channel 1 is set, then branch to OS_Tick_Handler.
+     * Otherwise, just execute common_rtc_irq_handler.
+     * This function has to be written in assembly and tagged as naked because OS_Tick_Handler
+     * will never return.
+     * A c function would put lr on the stack before calling OS_Tick_Handler and this value
+     * would never been dequeued.
+     *
+     * \code
+     * void COMMON_RTC_IRQ_HANDLER(void) {
+         if(NRF_RTC1->EVENTS_COMPARE[1]) {
+             // never return...
+             OS_Tick_Handler();
+         } else {
+             common_rtc_irq_handler();
+         }
+       }
+     * \endcode
+     */
+    __asm__ (
+        "ldr r0,=0x40011144\n"
+        "ldr r1, [r0, #0]\n"
+        "cmp r1, #0\n"
+        "beq US_TICKER_HANDLER\n"
+        "bl OS_Tick_Handler\n"
+    "US_TICKER_HANDLER:\n"
+        "push {r3, lr}\n"
+        "bl common_rtc_irq_handler\n"
+        "pop {r3, pc}\n"
+        "nop"
+    );
+}
+
+#elif defined (__ICCARM__)//IAR
+void common_rtc_irq_handler(void);
+
+__stackless __task void COMMON_RTC_IRQ_HANDLER(void)
+{
+    uint32_t temp;
+
+    __asm volatile(
+    "   ldr  %[temp], [%[reg2check]] \n"
+    "   cmp  %[temp], #0             \n"
+    "   beq  1f                      \n"
+    "   bl.w OS_Tick_Handler            \n"
+    "1:                             \n"
+    "   push {r3, lr}\n"
+    "   blx %[rtc_irq] \n"
+    "   pop {r3, pc}\n"
+
+    : /* Outputs */
+    [temp] "=&r"(temp)
+    : /* Inputs */
+    [reg2check] "r"(0x40011144),
+    [rtc_irq] "r"(common_rtc_irq_handler)
+    : /* Clobbers */
+    "cc"
+    );
+    (void)temp;
+}
+
+
+#else
+
+#error Compiler not supported.
+#error Provide a definition of COMMON_RTC_IRQ_HANDLER.
+
+/*
+ * Chanel 1 of RTC1 is used by RTX as a systick.
+ * If the compare event on channel 1 is set, then branch to OS_Tick_Handler.
+ * Otherwise, just execute common_rtc_irq_handler.
+ * This function has to be written in assembly and tagged as naked because OS_Tick_Handler
+ * will never return.
+ * A c function would put lr on the stack before calling OS_Tick_Handler and this value
+ * will never been dequeued. After a certain time a stack overflow will happen.
+ *
+ * \code
+ * void COMMON_RTC_IRQ_HANDLER(void) {
+     if(NRF_RTC1->EVENTS_COMPARE[1]) {
+         // never return...
+         OS_Tick_Handler();
+     } else {
+         common_rtc_irq_handler();
+     }
+   }
+ * \endcode
+ */
+
+#endif
+
+/**
+ * Return the next number of clock cycle needed for the next tick.
+ * @note This function has been carrefuly optimized for a systick occuring every 1000us.
+ */
+static uint32_t get_next_tick_cc_delta() {
+    uint32_t delta = 0;
+
+    if (os_clockrate != 1000) {
+        // In RTX, by default SYSTICK is is used.
+        // A tick event is generated  every os_trv + 1 clock cycles of the system timer.
+        delta = os_trv + 1;
+    } else {
+        // If the clockrate is set to 1000us then 1000 tick should happen every second.
+        // Unfortunatelly, when clockrate is set to 1000, os_trv is equal to 31.
+        // If (os_trv + 1) is used as the delta value between two ticks, 1000 ticks will be
+        // generated in 32000 clock cycle instead of 32768 clock cycles.
+        // As a result, if a user schedule an OS timer to start in 100s, the timer will start
+        // instead after 97.656s
+        // The code below fix this issue, a clock rate of 1000s will generate 1000 ticks in 32768
+        // clock cycles.
+        // The strategy is simple, for 1000 ticks:
+        //   * 768 ticks will occur 33 clock cycles after the previous tick
+        //   * 232 ticks will occur 32 clock cycles after the previous tick
+        // By default every delta is equal to 33.
+        // Every five ticks (20%, 200 delta in one second), the delta is equal to 32
+        // The remaining (32) deltas equal to 32 are distributed using primes numbers.
+        static uint32_t counter = 0;
+        if ((counter % 5) == 0 || (counter % 31) == 0 || (counter % 139) == 0 || (counter == 503)) {
+            delta = 32;
+        } else {
+            delta = 33;
+        }
+        ++counter;
+        if (counter == 1000) {
+            counter = 0;
+        }
+    }
+    return delta;
+}
+
+static inline void clear_tick_interrupt() {
+    nrf_rtc_event_clear(COMMON_RTC_INSTANCE, OS_TICK_EVENT);
+    nrf_rtc_event_disable(COMMON_RTC_INSTANCE, OS_TICK_INT_MASK);
+}
+
+/**
+ * Indicate if a value is included in a range which can be wrapped.
+ * @param  begin start of the range
+ * @param  end   end of the range
+ * @param  val   value to check
+ * @return       true if the value is included in the range and false otherwise.
+ */
+static inline bool is_in_wrapped_range(uint32_t begin, uint32_t end, uint32_t val) {
+    // regular case, begin < end
+    // return true if  begin <= val < end
+    if (begin < end) {
+        if (begin <= val && val < end) {
+            return true;
+        } else {
+            return false;
+        }
+    } else {
+        // In this case end < begin because it has wrap around the limits
+        // return false if end < val < begin
+        if (end < val && val < begin)  {
+            return false;
+        } else {
+            return true;
+        }
+    }
+
+}
+
+/**
+ * Register the next tick.
+ */
+static void register_next_tick() {
+    previous_tick_cc_value = nrf_rtc_cc_get(COMMON_RTC_INSTANCE, OS_TICK_CC_CHANNEL);
+    uint32_t delta = get_next_tick_cc_delta();
+    uint32_t new_compare_value = (previous_tick_cc_value + delta) & MAX_RTC_COUNTER_VAL;
+
+    // Disable irq directly for few cycles,
+    // Validation of the new CC value against the COUNTER,
+    // Setting the new CC value and enabling CC IRQ should be an atomic operation
+    // Otherwise, there is a possibility to set an invalid CC value because
+    // the RTC1 keeps running.
+    // This code is very short 20-38 cycles in the worst case, it shouldn't
+    // disturb softdevice.
+    __disable_irq();
+    uint32_t current_counter = nrf_rtc_counter_get(COMMON_RTC_INSTANCE);
+
+    // If an overflow occur, set the next tick in COUNTER + delta clock cycles
+    if (is_in_wrapped_range(previous_tick_cc_value, new_compare_value, current_counter + 1) == false) {
+        new_compare_value = current_counter + delta;
+    }
+    nrf_rtc_cc_set(COMMON_RTC_INSTANCE, OS_TICK_CC_CHANNEL, new_compare_value);
+    // Enable generation of the compare event for the value set above (this
+    // event will trigger the interrupt).
+    nrf_rtc_event_enable(COMMON_RTC_INSTANCE, OS_TICK_INT_MASK);
+    __enable_irq();
+}
+
+/**
+ * Initialize alternative hardware timer as RTX kernel timer
+ * This function is directly called by RTX.
+ * @note this function shouldn't be called directly.
+ * @return  IRQ number of the alternative hardware timer
+ */
+int os_tick_init (void)
+{
+    common_rtc_init();
+
+    nrf_rtc_cc_set(COMMON_RTC_INSTANCE, OS_TICK_CC_CHANNEL, 0);
+    register_next_tick();
+
+    return nrf_drv_get_IRQn(COMMON_RTC_INSTANCE);
+}
+
+/**
+ * Acknowledge the tick interrupt.
+ * This function is called by the function OS_Tick_Handler of RTX.
+ * @note this function shouldn't be called directly.
+ */
+void os_tick_irqack(void)
+{
+    clear_tick_interrupt();
+    register_next_tick();
+}
+
+/**
+ * Returns the overflow flag of the alternative hardware timer.
+ * @note This function is exposed by RTX kernel.
+ * @return 1 if the timer has overflowed and 0 otherwise.
+ */
+uint32_t os_tick_ovf(void) {
+    uint32_t current_counter = nrf_rtc_counter_get(COMMON_RTC_INSTANCE);
+    uint32_t next_tick_cc_value = nrf_rtc_cc_get(COMMON_RTC_INSTANCE, OS_TICK_CC_CHANNEL);
+
+    return is_in_wrapped_range(previous_tick_cc_value, next_tick_cc_value, current_counter) ? 0 : 1;
+}
+
+/**
+ * Return the value of the alternative hardware timer.
+ * @note The documentation is not very clear about what is expected as a result,
+ * is it an ascending counter, a descending one ?
+ * None of this is specified.
+ * The default systick is a descending counter and this function return values in
+ * descending order, even if the internal counter used is an ascending one.
+ * @return the value of the alternative hardware timer.
+ */
+uint32_t os_tick_val(void) {
+    uint32_t current_counter = nrf_rtc_counter_get(COMMON_RTC_INSTANCE);
+    uint32_t next_tick_cc_value = nrf_rtc_cc_get(COMMON_RTC_INSTANCE, OS_TICK_CC_CHANNEL);
+
+    // do not use os_tick_ovf because its counter value can be different
+    if(is_in_wrapped_range(previous_tick_cc_value, next_tick_cc_value, current_counter)) {
+        if (next_tick_cc_value > previous_tick_cc_value) {
+            return next_tick_cc_value - current_counter;
+        } else if(current_counter <= next_tick_cc_value) {
+            return next_tick_cc_value - current_counter;
+        } else {
+            return next_tick_cc_value + (MAX_RTC_COUNTER_VAL - current_counter);
+        }
+    } else {
+        // use (os_trv + 1) has the base step, can be totally inacurate ...
+        uint32_t clock_cycles_by_tick = os_trv + 1;
+
+        // if current counter has wrap arround, add the limit to it.
+        if (current_counter < next_tick_cc_value) {
+            current_counter = current_counter + MAX_RTC_COUNTER_VAL;
+        }
+
+        return clock_cycles_by_tick - ((current_counter - next_tick_cc_value) % clock_cycles_by_tick);
+    }
+
+}
+
+#endif // defined(TARGET_MCU_NRF51822)