source: rtems/c/src/lib/libbsp/m68k/gen68340/clock/ckinit.c @ c6fb8ed4

/*
 * This routine initializes the MC68340/349 Periodic Interval Timer
 *
 * Based on the `gen68360' board support package, and covered by the
 * original distribution terms.
 *
 * Geoffroy Montel
 * France Telecom - CNET/DSM/TAM/CAT
 * 4, rue du Clos Courtel
 * 35512 CESSON-SEVIGNE
 * FRANCE
 *
 * e-mail: g_montel@yahoo.com
 *
 *  $Id$
 */

/*
 * Input parameters:    NONE
 *
 * Output parameters:   NONE
 *
 * COPYRIGHT (c) 1989-1999.
 * On-Line Applications Research Corporation (OAR).
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://www.rtems.com/license/LICENSE.
 */

#include <stdlib.h>                     /* for atexit() */
#include <bsp.h>
#include <m68340.h>

#define CLOCK_VECTOR    120             /* clock isr routine vector in the vbr */
#define CLOCK_IRQ_LEVEL 6               /* clock isr level */

/*
 * Clock_driver_ticks is a monotonically increasing counter of the
 * number of clock ticks since the driver was initialized.
 */
volatile uint32_t         Clock_driver_ticks;

/*
 * These are set by clock driver during its init
 */
rtems_device_major_number rtems_clock_major = ~0;
rtems_device_minor_number rtems_clock_minor;

/*
 * Periodic interval timer interrupt handler
 */

/******************************************************
  Name: Clock_isr
  Input parameters: irq vector
  Output parameters: none
  Description: update # of clock ticks
 *****************************************************/
rtems_isr
Clock_isr (rtems_vector_number vector)
{
        /*
         * Announce the clock tick
         */
        Clock_driver_ticks++;
        rtems_clock_tick();
}

/******************************************************
  Name: clock_exit
  Input parameters: -
  Output parameters: -
  Description: turn off periodic time at shutdown
 *****************************************************/
void
Clock_exit (void)
{
        /*
         * Turn off periodic interval timer
         */
        SIMPITR = 0;
}

/******************************************************
  Name: Install_clock
  Input parameters: the Clock Interrupt Subroutine
  Output parameters: -
  Description: initialize the periodic interval ticker
               called by Clock_Initialize
 *****************************************************/
static void
Install_clock (rtems_isr_entry clock_isr)
{
        uint32_t   pitr_tmp;
        uint32_t   usecs_per_tick;

        Clock_driver_ticks = 0;

        set_vector (clock_isr, CLOCK_VECTOR, 1);

        /* sets the Periodic Interrupt Control Register PICR */
        /* voir a quoi correspond exactement le Clock Vector */

        SIMPICR = ( CLOCK_IRQ_LEVEL << 8 ) | ( CLOCK_VECTOR );

        /* sets the PITR count value */
        /* this assumes a 32.765 kHz crystal */

        usecs_per_tick = rtems_configuration_get_microseconds_per_tick();
        /* find out whether prescaler should be enabled or not */
        if ( usecs_per_tick <= 31128 ) {
           pitr_tmp = ( usecs_per_tick * 8192 ) / 1000000 ;
        } else {
           pitr_tmp = ( usecs_per_tick / 1000000 ) * 16;
           /* enable it */
           pitr_tmp |= 0x100;
        }

        SIMPITR = (unsigned char) pitr_tmp;

        atexit (Clock_exit);
}

/******************************************************
  Name: Clock_initialize
  Input parameters: major & minor numbers
  Output parameters: -
  Description: main entry for clock initialization
               calls the bsp dependant routine
 *****************************************************/
rtems_device_driver
Clock_initialize(
        rtems_device_major_number major,
        rtems_device_minor_number minor,
        void *pargp
)
{
        Install_clock (Clock_isr);

        /*
         * make major/minor avail to others such as shared memory driver
         */
        rtems_clock_major = major;
        rtems_clock_minor = minor;

        return RTEMS_SUCCESSFUL;
}