source: rtems/c/src/lib/libbsp/m68k/gen68360/clock/ckinit.c @ b1b5a7cb

/* 
 * This routine initializes the MC68360 Periodic Interval Timer
 *
 * The PIT has rather poor resolution, but it is easy to set up
 * and requires no housekeeping once it is going.
 *
 * Based on the `gen68302' board support package, and covered by the
 * original distribution terms.
 *
 * W. Eric Norum
 * Saskatchewan Accelerator Laboratory
 * University of Saskatchewan
 * Saskatoon, Saskatchewan, CANADA
 * eric@skatter.usask.ca
 *
 *  $Id$
 */

/*
 * Input parameters:    NONE
 *
 * Output parameters:   NONE
 *
 * COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994.
 * On-Line Applications Research Corporation (OAR).
 * All rights assigned to U.S. Government, 1994.
 *
 * This material may be reproduced by or for the U.S. Government pursuant
 * to the copyright license under the clause at DFARS 252.227-7013.  This
 * notice must appear in all copies of this file and its derivatives.
 */

#include <stdlib.h>                     /* for atexit() */
#include <bsp.h>
#include <rtems/libio.h>
#include "m68360.h"

#define CLOCK_VECTOR    120
#define CLOCK_IRQ_LEVEL 6

/*
 * Clock_driver_ticks is a monotonically increasing counter of the
 * number of clock ticks since the driver was initialized.
 */
volatile rtems_unsigned32 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
 */
rtems_isr
Clock_isr (rtems_vector_number vector)
{
        Clock_driver_ticks++;
        rtems_clock_tick();
}

void
Clock_exit (void)
{
        if (BSP_Configuration.ticks_per_timeslice ) {
                /*
                 * Turn off periodic interval timer
                 */
                m360.pitr &= ~0xFF;
        }
}

static void
Install_clock (rtems_isr_entry clock_isr)
{
        Clock_driver_ticks = 0;
        if ( BSP_Configuration.ticks_per_timeslice ) {
                int pitr;

                /*
                 * Choose periodic interval timer register value
                 * For a 25 MHz external clock the basic clock rate is
                 *      40 nsec * 128 * 4 = 20.48 usec/tick
                 */
                pitr = ((BSP_Configuration.microseconds_per_tick * 100) + 1023) / 2048;
                if (pitr >= 256) {
                        pitr = (pitr + 255) / 512;
                        if (pitr >= 256)
                                pitr = 255;
                        else if (pitr == 0)
                                pitr = 1;
                        pitr |= 0x100;
                }
                else if (pitr == 0) {
                        pitr = 1;
                }
                m360.pitr &= ~0x1FF;
                m360.picr = (CLOCK_IRQ_LEVEL << 8) | CLOCK_VECTOR;
                set_vector (clock_isr, CLOCK_VECTOR, 1);
                m360.pitr |= pitr;
                atexit (Clock_exit);
        }
}

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) {
                /*
                 * 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 );
                }
        }
        return RTEMS_SUCCESSFUL;
}