| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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. |
| */ |
| |
| /** |
| * NOTE: Unlike other MCUs, this one does not use SysTick to implement the |
| * tickless idle state. The SysTick timer uses HCLK as its source, and HCLK is |
| * gated while this MCU is in deep sleep (e.g., during a `wfi` instruction). |
| * |
| * To enable a wake up from deep sleep, the idle state is instead implemented |
| * using this MCU's system timer (STIMER) with LFRC as the source. |
| */ |
| |
| #include <assert.h> |
| #include "os/mynewt.h" |
| #include "mcu/system_apollo2.h" |
| #include "hal/hal_os_tick.h" |
| #include "mcu/cmsis_nvic.h" |
| |
| #include "am_mcu_apollo.h" |
| |
| #define APOLLO2_OS_TICK_FREQ 1024 /* Hz */ |
| #define APOLLO2_OS_TICK_IRQ STIMER_CMPR0_IRQn |
| |
| /*** Value of timer when the ISR last executed. */ |
| static uint32_t apollo2_os_tick_prev; |
| |
| /*** Number of system ticks per single OS tick. */ |
| static uint32_t apollo2_os_tick_dur; |
| |
| static void |
| apollo2_os_tick_set_timer(int os_ticks) |
| { |
| uint32_t sys_ticks; |
| uint32_t cfg; |
| |
| OS_ASSERT_CRITICAL(); |
| |
| sys_ticks = os_ticks * apollo2_os_tick_dur; |
| |
| /* Freeze time, set timer expiry, then unfreeze time. */ |
| cfg = am_hal_stimer_config(AM_HAL_STIMER_CFG_FREEZE); |
| am_hal_stimer_compare_delta_set(0, sys_ticks); |
| am_hal_stimer_config(cfg); |
| } |
| |
| static void |
| apollo2_os_tick_handler(void) |
| { |
| uint32_t cur; |
| int os_ticks; |
| int delta; |
| os_sr_t sr; |
| |
| OS_ENTER_CRITICAL(sr); |
| |
| /* Calculate elapsed ticks and advance OS time. */ |
| cur = am_hal_stimer_counter_get(); |
| delta = cur - apollo2_os_tick_prev; |
| os_ticks = delta / apollo2_os_tick_dur; |
| os_time_advance(os_ticks); |
| |
| /* Clear timer interrupt. */ |
| am_hal_stimer_int_clear(AM_HAL_STIMER_INT_COMPAREA); |
| |
| /* Update the time associated with the most recent tick. */ |
| apollo2_os_tick_prev += os_ticks * apollo2_os_tick_dur; |
| |
| /* Schedule timer to interrupt at the next tick. */ |
| apollo2_os_tick_set_timer(1); |
| |
| OS_EXIT_CRITICAL(sr); |
| } |
| |
| void |
| os_tick_idle(os_time_t ticks) |
| { |
| OS_ASSERT_CRITICAL(); |
| |
| /* Since the STIMER only uses relative scheduling, all ticks values are |
| * valid. There is no need to check for wrap around. |
| */ |
| |
| /* Only set the timer for nonzero tick values. For values of 0, just let |
| * the timer expire on the next tick, as scheduled earlier. |
| */ |
| if (ticks > 0) { |
| apollo2_os_tick_set_timer(ticks); |
| } |
| |
| __DSB(); |
| __WFI(); |
| |
| if (ticks > 0) { |
| apollo2_os_tick_handler(); |
| } |
| } |
| |
| void |
| os_tick_init(uint32_t os_ticks_per_sec, int prio) |
| { |
| os_sr_t sr; |
| |
| /* Reset the timer to 0. */ |
| am_hal_stimer_counter_clear(); |
| |
| /* The OS tick timer uses: |
| * o The 1024 Hz low-frequency RC oscillator (LFRC) |
| * o The first comparator (COMPAREA) |
| */ |
| am_hal_stimer_config(AM_HAL_STIMER_LFRC_1KHZ | |
| AM_HAL_STIMER_CFG_COMPARE_A_ENABLE); |
| am_hal_stimer_int_enable(AM_HAL_STIMER_INT_COMPAREA); |
| |
| apollo2_os_tick_dur = APOLLO2_OS_TICK_FREQ / os_ticks_per_sec; |
| |
| /* Enable the STIMER interrupt in the NVIC. */ |
| NVIC_SetPriority(APOLLO2_OS_TICK_IRQ, prio); |
| NVIC_SetVector(APOLLO2_OS_TICK_IRQ, (uint32_t)apollo2_os_tick_handler); |
| NVIC_EnableIRQ(APOLLO2_OS_TICK_IRQ); |
| |
| /* Schedule timer to interrupt at the next tick. */ |
| OS_ENTER_CRITICAL(sr); |
| apollo2_os_tick_set_timer(1); |
| OS_EXIT_CRITICAL(sr); |
| } |