nuttx/arch/arm/src/lpc54xx/lpc54_timerisr.c

/****************************************************************************
 * arch/arm/src/lpc54xx/lpc54_timerisr.c
 *
 *   Copyright (C) 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/lpc54_syscon.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/* The SysTick clock may be clocked internally either by the by the system
 * clock (CLKSOURCE==1) or by the SysTick function clock (CLKSOURCE==0).
 * The SysTick Function clock is equal to:
 *
 *   Fsystick = Fmainclk / SYSTICKCLKDIV
 *
 * Both the divider value (BOARD_SYSTICKCLKDIV) and the resulting SysTick
 * function clock frequency (Fsystick, BOARD_SYSTICK_CLOCK)
 *
 * 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
 *
 * Tips for selecting BOARD_SYSTICKCLKDIV:  The resulting reload value
 * should be as large as possible, but must be less than 2^24:
 *
 *   SYSTICKDIV > Fmainclk / CLK_TCK / 2^24
 */

#define SYSTICK_RELOAD ((BOARD_SYSTICK_CLOCK / 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:  lpc54_timerisr
 *
 * Description:
 *   The timer ISR will perform a variety of services for various portions
 *   of the systems.
 *
 ****************************************************************************/

static int lpc54_timerisr(int irq, uint32_t *regs, 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;

  /* May be clocked internally by the system clock or the SysTick function
   * clock.  Set the SysTick clock divider in the SYSCON_SYSTICK register.
   * Since this function is called early after reset, it is safe to assume
   * that the SysTick is disabled and so that no reset or halt actions are
   * necessary.
   */

  regval = (SYSCON_SYSTICKCLKDIV_DIV(BOARD_SYSTICKCLKDIV) |
            SYSCON_SYSTICKCLKDIV_REQFLAG);
  putreg32(regval, LPC54_SYSCON_SYSTICKCLKDIV);

  /* The request flag will be cleared when the divider change is complete */

  while ((getreg32(LPC54_SYSCON_SYSTICKCLKDIV) & SYSCON_SYSTICKCLKDIV_REQFLAG) != 0)
    {
    }

  /* Make sure that the SYSTICK clock source is set to use the SysTick
   * function clock (CLKSOURCE==0).
   */

  regval  = getreg32(NVIC_SYSTICK_CTRL);
  regval &= ~NVIC_SYSTICK_CTRL_CLKSOURCE;
  putreg32(regval, NVIC_SYSTICK_CTRL);

  /* Configure SysTick to interrupt at the requested rate */

  putreg32(SYSTICK_RELOAD, NVIC_SYSTICK_RELOAD);

  /* Attach the timer interrupt vector */

  (void)irq_attach(LPC54_IRQ_SYSTICK, (xcpt_t)lpc54_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(LPC54_IRQ_SYSTICK);
}