source: rtems/c/src/lib/libbsp/m68k/efi68k/clock/ckinit.c @ a2016b99

/*  Clock_init()
 *
 *  This routine initializes the DP8570A periodic interrupt on the 
 *  efi68k board. The tick frequency is 1 millisecond.
 *
 *  Input parameters:  NONE
 *
 *  Output parameters:  NONE
 *
 *  COPYRIGHT (c) 1989-1997.
 *  On-Line Applications Research Corporation (OAR).
 *  Copyright assigned to U.S. Government, 1994.
 *
 *  The license and distribution terms for this file may in
 *  the file LICENSE in this distribution or at
 *  http://www.OARcorp.com/rtems/license.html.
 *
 *  $Id$
 */

#include <stdlib.h>
#include <bsp.h>
#include <rtems/libio.h>

#define CLOCK_VECTOR  (TCP_ISR_LEVEL+24)

rtems_unsigned32 Clock_isrs;        /* ISRs until next tick */
volatile rtems_unsigned32 Clock_driver_ticks;
                                    /* ticks since initialization */
rtems_isr_entry  Old_ticker;

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


void per_interrupt(void)
{
  Clock_driver_ticks += 1;

  *MSR = PER;

  if ( Clock_isrs == 1 ) {
    rtems_clock_tick();
    Clock_isrs = BSP_Configuration.microseconds_per_tick / 1000;
  }
  else
    Clock_isrs -= 1;
}

rtems_isr Clock_isr(
  rtems_vector_number vector
)
{
  unsigned char entry_msr, msr;

  entry_msr = *MSR;
  *MSR = 0;
  while ( (msr=*MSR) & INT )
    /* test enabled interrupt bits */
    if (msr & PER)
      per_interrupt();
    else if (msr & T0) {
      *MSR = T0;                /* reset interrupt */
      Timer_interrupts++;       /* inc wrap around counter */
    }
    else      
      /* there has been an error if we reach this point */
      /* default action: reset all the interrupts */
      *MSR = ( PER | AL | T0 | T1 );
  *MSR = entry_msr & (RS | PS);
}

void Install_clock(
  rtems_isr_entry clock_isr
)
{
  Clock_driver_ticks = 0;
  Clock_isrs = BSP_Configuration.microseconds_per_tick / 1000;

  if ( BSP_Configuration.ticks_per_timeslice ) {
    Old_ticker = (rtems_isr_entry) set_vector( clock_isr, CLOCK_VECTOR, 1 );

    *MSR = RS;                  /* enable 1mS interrupts */
    *ICR0 |= OME;

    atexit( Clock_exit );
  }
}

void Clock_exit( void )
{

  if ( BSP_Configuration.ticks_per_timeslice ) {

    /* shutdown periodic interrupt */
    *MSR = RS;
    *ICR0 &= 0xc0;
    /* do not restore old vector */

  }
}

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;
}
 
rtems_device_driver Clock_control(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void *pargp
)
{
    rtems_unsigned32 isrlevel;
    rtems_libio_ioctl_args_t *args = pargp;
 
    if (args == 0)
        goto done;
 
    /*
     * This is hokey, but until we get a defined interface
     * to do this, it will just be this simple...
     */
 
    if (args->command == rtems_build_name('I', 'S', 'R', ' '))
    {
        Clock_isr(CLOCK_VECTOR);
    }
    else if (args->command == rtems_build_name('N', 'E', 'W', ' '))
    {
      rtems_interrupt_disable( isrlevel );
       (void) set_vector( args->buffer, CLOCK_VECTOR, 1 );
      rtems_interrupt_enable( isrlevel );
    }
 
done:
    return RTEMS_SUCCESSFUL;
}