text: /****************************************************************************
   * arch/hc/src/m9s12/m9s12_timerisr.c
   *
   *   Copyright (C) 2011 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 "clock/clock.h"
  #include "up_internal.h"
  #include "up_arch.h"
  
  #include "chip.h"
  #include "m9s12_internal.h"
  #include "m9s12_crg.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 timer frequency is the OSCCLK divided down.  The divisor is
   * (A+1)*(2**(B+9)) where:
   *
   *   A = MODCNT RTR[0:3]
   *   B = PREP   RTR[4:6]
   *
   * Maximum and minimum values:
   */
  
  #define MIN_PRER    1024 /* 2**10, B=1 */
  #define MAX_PRER   65536 /* 2**16, B=7 */
  
  #define MIN_MODCNT     1 /* A=0 */
  #define MAX_MODCNT    16 /* A=15 */
  
  /* Pick the smallest value of B for which:
   *
   *   OSCCLK/(MAX_MODCNT*(2**(B+9))) >= CLK_TCK >= OSCCLK/(MIN_MODCNT*(2**(B+9)))
   */
  
  #if CLK_TCK >= HCS12_OSCCLK/(MAX_MODCNT*1024) && HCS12_OSCCLK/(MIN_MODCNT*1024)
  #  define PRER_VALUE      1
  #  define PRER_DIV     1024
  #elif CLK_TCK >= HCS12_OSCCLK/(MAX_MODCNT*2048) && HCS12_OSCCLK/(MIN_MODCNT*2048)
  #  define PRER_VALUE      2
  #  define PRER_DIV     2048
  #elif CLK_TCK >= HCS12_OSCCLK/(MAX_MODCNT*4096) && HCS12_OSCCLK/(MIN_MODCNT*4096)
  #  define PRER_VALUE      3
  #  define PRER_DIV     4096
  #elif CLK_TCK >= HCS12_OSCCLK/(MAX_MODCNT*8192) && HCS12_OSCCLK/(MIN_MODCNT*8192)
  #  define PRER_VALUE      4
  #  define PRER_DIV     8192
  #elif CLK_TCK >= HCS12_OSCCLK/(MAX_MODCNT*16384) && HCS12_OSCCLK/(MIN_MODCNT*16384)
  #  define PRER_VALUE      5
  #  define PRER_DIV    16384
  #elif CLK_TCK >= HCS12_OSCCLK/(MAX_MODCNT*32768) && HCS12_OSCCLK/(MIN_MODCNT*32768)
  #  define PRER_VALUE      6
  #  define PRER_DIV    32768
  #elif CLK_TCK >= HCS12_OSCCLK/(MAX_MODCNT*65536) && HCS12_OSCCLK/(MIN_MODCNT*65536)
  #  define PRER_VALUE      7
  #  define PRER_DIV    65536
  #else
  #  error "Cannot generate CLK_TCK from HCSCLK_OSCCLK"
  #endif
  
  /* Now we can simply calculate A from:
   *
   * CLK_TCK = OSCCLK/((A+1)*PRER_DIV)
   * OSCCLK / (CLK_TCK * PRER_DIV) - 1
   */
  
   #define MODCNT_DENOM  ((uint32_t)CLK_TCK * (uint32_t)PRER_DIV)
   #define MODCNT_VALUE  ((((uint32_t)HCS12_OSCCLK  + (MODCNT_DENOM/2))/ MODCNT_DENOM) - 1)
  
  /****************************************************************************
   * Private Types
   ****************************************************************************/
  
  /****************************************************************************
   * Private Function Prototypes
   ****************************************************************************/
  
  /****************************************************************************
   * Global Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Function:  up_timerisr
   *
   * Description:
   *   The timer ISR will perform a variety of services for various portions
   *   of the systems.
   *
   ****************************************************************************/
  
  int up_timerisr(int irq, uint32_t *regs)
  {
    /* Clear real time interrupt flag */
  
    putreg8(CRG_CRGFLG_RTIF, HCS12_CRG_CRGFLG);
  
    /* Process timer interrupt */
  
    sched_process_timer();
    return 0;
  }
  
  /****************************************************************************
   * Function:  up_timer_initialize
   *
   * Description:
   *   This function is called during start-up to initialize the system timer
   *   interrupt.
   *
   ****************************************************************************/
  
  void up_timer_initialize(void)
  {
    uint32_t tmp;
    uint8_t  regval;
  
    /* Configure hardware RTI timer (with a hack to avoid and integer overflow
     * error at compile time.. hopefully the optimizer will eliminate these
     * uint32_t operations).
     */
  
    tmp = MODCNT_VALUE << CRG_RTICTL_MODCNT_SHIFT | PRER_VALUE << CRG_RTICTL_PRER_SHIFT;
    putreg8((uint8_t)tmp, HCS12_CRG_RTICTL);
  
    /* Attach the timer interrupt vector */
  
    (void)irq_attach(HCS12_IRQ_VRTI, (xcpt_t)up_timerisr);
  
    /* Enable RTI interrupt by setting the RTIE bit */
  
    regval  = getreg8(HCS12_CRG_CRGINT);
    regval |= CRG_CRGINT_RTIE;
    putreg8(regval, HCS12_CRG_CRGINT);
  }
  