nuttx/arch/arm/src/samdl/sam_timerisr.c

/****************************************************************************
 * arch/arm/src/samdl/sam_timerisr.c
 *
 *   Copyright (C) 2014, 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"

/****************************************************************************
 * 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).
 *
 * Then, for example, if the CPU clock is the the SysTick and
 * BOARD_CPU_FREQUENCY is 48MHz and CLK_TCK is 100, then the reload value
 * would be:
 *
 *   SYSTICK_RELOAD = (48,000,000 / 100) - 1
 *                  = 479,999
 *                  = 0x752ff
 *
 * Which fits within the maximum 24-bit reload value.
 */

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

static int sam_timerisr(int irq, uint32_t *regs)
{
  /* 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(ARMV6M_SYSCON_SHPR3);
  regval &= ~SYSCON_SHPR3_PRI_15_MASK;
  regval |= (NVIC_SYSH_PRIORITY_DEFAULT << SYSCON_SHPR3_PRI_15_SHIFT);
  putreg32(regval, ARMV6M_SYSCON_SHPR3);

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

  putreg32(SYSTICK_RELOAD, ARMV6M_SYSTICK_RVR);

  /* Attach the timer interrupt vector */

  (void)irq_attach(SAM_IRQ_SYSTICK, (xcpt_t)sam_timerisr);

  /* Enable SysTick interrupts */

  putreg32((SYSTICK_CSR_TICKINT | SYSTICK_CSR_ENABLE), ARMV6M_SYSTICK_CSR);

  /* And enable the timer interrupt */

  up_enable_irq(SAM_IRQ_SYSTICK);
}