text: /****************************************************************************
   * arch/arm/src/kinetis/kinetis_timerisr.c
   *
   *   Copyright (C) 2011, 2017 Gregory Nutt. All rights reserved.
   *   Author: Gregory Nutt <gnutt@nuttx.org>
   *
   * 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 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 NuttX nor the names of its contributors may be
   *    used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * 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 OWNER 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.
   *
   ****************************************************************************/
  
  /****************************************************************************
   * Included Files
   ****************************************************************************/
  
  #include <nuttx/config.h>
  
  #include <stdint.h>
  #include <time.h>
  #include <debug.h>
  
  #include <nuttx/arch.h>
  #include <arch/board/board.h>
  
  #include "nvic.h"
  #include "clock/clock.h"
  #include "up_internal.h"
  #include "up_arch.h"
  
  #include "chip.h"
  #include "kinetis.h"
  
  /****************************************************************************
   * Pre-processor Definitions
   ****************************************************************************/
  
  /* The desired timer interrupt frequency is provided by the definition
   * CLK_TCK (see include/time.h).  CLK_TCK defines the desired number of
   * system clock ticks per second.  That value is a user configurable setting
   * that defaults to 100 (100 ticks per second = 10 MS interval).
   *
   * The Clock Source: The System Tick Timer's clock source is always the core
   * clock
   */
  
  #define SYSTICK_RELOAD ((BOARD_CORECLK_FREQ / CLK_TCK) - 1)
  
  /* The size of the reload field is 24 bits.  Verify that the reload value
   * will fit in the reload register.
   */
  
  #if SYSTICK_RELOAD > 0x00ffffff
  #  error SYSTICK_RELOAD exceeds the range of the RELOAD register
  #endif
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Function:  kinetis_timerisr
   *
   * Description:
   *   The timer ISR will perform a variety of services for various portions
   *   of the systems.
   *
   ****************************************************************************/
  
  static int kinetis_timerisr(int irq, uint32_t *regs, FAR void *arg)
  {
    /* Process timer interrupt */
  
    sched_process_timer();
    return 0;
  }
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Function:  arm_timer_initialize
   *
   * Description:
   *   This function is called during start-up to initialize
   *   the timer interrupt.
   *
   ****************************************************************************/
  
  void arm_timer_initialize(void)
  {
    uint32_t regval;
  
    /* Set the SysTick interrupt to the default priority */
  
    regval = getreg32(NVIC_SYSH12_15_PRIORITY);
    regval &= ~NVIC_SYSH_PRIORITY_PR15_MASK;
    regval |= (NVIC_SYSH_PRIORITY_DEFAULT << NVIC_SYSH_PRIORITY_PR15_SHIFT);
    putreg32(regval, NVIC_SYSH12_15_PRIORITY);
  
    /* Note that is should not be neccesary to set the SYSTICK clock source:
     * "The CLKSOURCE bit in SysTick Control and Status register is always set
     *  to select the core clock."
     */
  
  #if 0
    regval = getreg32(NVIC_SYSTICK_CTRL);
    regval |= NVIC_SYSTICK_CTRL_CLKSOURCE;
    putreg32(regval, NVIC_SYSTICK_CTRL);
  #endif
  
    /* Configure SysTick to interrupt at the requested rate */
  
    putreg32(SYSTICK_RELOAD, NVIC_SYSTICK_RELOAD);
  
    /* Attach the timer interrupt vector */
  
    (void)irq_attach(KINETIS_IRQ_SYSTICK, (xcpt_t)kinetis_timerisr, NULL);
  
    /* Enable SysTick interrupts */
  
    putreg32((NVIC_SYSTICK_CTRL_CLKSOURCE | NVIC_SYSTICK_CTRL_TICKINT |
              NVIC_SYSTICK_CTRL_ENABLE),
             NVIC_SYSTICK_CTRL);
  
    /* And enable the timer interrupt */
  
    up_enable_irq(KINETIS_IRQ_SYSTICK);
  }
  