text: /****************************************************************************
   * arch/arm/src/s32k1xx/s32k14x/s32k14x_timerisr.c
   *
   *   Copyright (C) 2019 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 <assert.h>
  #include <debug.h>
  
  #include <nuttx/arch.h>
  #include <arch/board/board.h>
  
  #include "nvic.h"
  #include "up_internal.h"
  #include "up_arch.h"
  
  #include "clock/clock.h"
  #include "s32k1xx_clockconfig.h"
  
  /****************************************************************************
   * Pre-processor Definitions
   ****************************************************************************/
  
  /* The SysTick clock input (Fsystick) is determined by the CLKSOURCE file of
   * the SysTick CSR register:  The CLKSOURCE field in SysTick Control and
   * Status register selects either the core clock (when CLKSOURCE = 1) or a
   * divide-by-16 of the core clock (when CLKSOURCE = 0).
   *
   * 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).
   *
   *    reload = (Fsystick / CLK_TICK) - 1
   */
  
  #define SYSTICK_RELOAD(coreclk) (((coreclk) / CLK_TCK) - 1)
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Function:  s32k14x_timerisr
   *
   * Description:
   *   The timer ISR will perform a variety of services for various portions
   *   of the systems.
   *
   ****************************************************************************/
  
  static int s32k14x_timerisr(int irq, uint32_t *regs, void *arg)
  {
    /* Process timer interrupt */
  
    nxsched_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 coreclk;
    uint32_t reload;
  
    /* Make sure that the SYSTICK clock source is set to use the SysTick
     * function clock (CLKSOURCE==1).
     */
  
    putreg32(NVIC_SYSTICK_CTRL_CLKSOURCE, NVIC_SYSTICK_CTRL);
  
    /* Get the reload value */
  
    coreclk = s32k1xx_get_coreclk();
    reload  = SYSTICK_RELOAD(coreclk);
  
    /* The size of the reload field is 24 bits. */
  
    DEBUGASSERT(reload <= 0x00ffffff);
  
    /* Configure SysTick to interrupt at the requested rate */
  
    putreg32(reload, NVIC_SYSTICK_RELOAD);
  
    /* Attach the timer interrupt vector */
  
    (void)irq_attach(S32K1XX_IRQ_SYSTICK, (xcpt_t)s32k14x_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(S32K1XX_IRQ_SYSTICK);
  }
  