Subversion Repositories openrisc_2011-10-31

/*

 * 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: ckinit.c,v 1.2 2001-09-27 12:00:08 chris Exp $

 */

/*

 * 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.OARcorp.com/rtems/license.html.

 */

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

#include <bsp.h>

#include <rtems/libio.h>

#include "m68360.h"

#define CLOCK_VECTOR    120

#define CLOCK_IRQ_LEVEL 4

/*

 * 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;

char M360DefaultWatchdogFeeder = 1;

/*

 * RTEMS and hardware have different notions of clock rate.

 */

static unsigned long rtems_nsec_per_tick;

static unsigned long pit_nsec_per_tick;

/*

 * Periodic interval timer interrupt handler

 */

rtems_isr

Clock_isr (rtems_vector_number vector)

{

        static unsigned long nsec;

        /*

         * See if it's really time for a `tick'

         */

        nsec += pit_nsec_per_tick;

        if (nsec >= rtems_nsec_per_tick) {

                nsec -= rtems_nsec_per_tick;

                /*

                 * Perform a dummy read of DPRAM.

                 * This works around a bug in Rev. B of the 68360

                 */

                m360.dpram0[0];

                /*

                 * Feed the watchdog

                 * Application code can override this by

                 * setting M360DefaultWatchdogFeeder to zero.

                 */

                if (M360DefaultWatchdogFeeder) {

                        m360.swsr = 0x55;

                        m360.swsr = 0xAA;

                }

                /*

                 * Announce the clock tick

                 */

                Clock_driver_ticks++;

                rtems_clock_tick();

        }

}

void

Clock_exit (void)

{

        /*

         * Turn off periodic interval timer

         */

        m360.pitr &= ~0xFF;

}

static void

Install_clock (rtems_isr_entry clock_isr)

{

        int divisor;

        extern int m360_clock_rate; /* This should be somewhere in a config file */

        unsigned long nsec_per_chip_tick = 1000000000 / m360_clock_rate;

        unsigned long nsec_per_pit_tick = 512 * nsec_per_chip_tick;

        Clock_driver_ticks = 0;

        /*

         * Choose periodic interval timer register value

         * The rate at which the periodic interval timer

         * can generate interrupts is almost certainly not

         * the same as desired by the BSP configuration.

         * Handle the difference by choosing the largest PIT

         * interval which is less than or equal to the RTEMS

         * interval and skipping some hardware interrupts.

         * To reduce the jitter in the calls to RTEMS the

         * hardware interrupt interval is never less than

         * the maximum non-prescaled value from the PIT.

         *

         * For a 25 MHz external clock the basic clock rate is

         *      40 nsec * 128 * 4 = 20.48 usec/tick

         */

        rtems_nsec_per_tick = BSP_Configuration.microseconds_per_tick * 1000;

        divisor = rtems_nsec_per_tick / nsec_per_pit_tick;

        if (divisor >= 256) {

                divisor = 255;

        } else if (divisor == 0) {

                divisor = 1;

        }

        pit_nsec_per_tick = nsec_per_pit_tick * divisor;

        m360.pitr &= ~0x1FF;

        m360.picr = (CLOCK_IRQ_LEVEL << 8) | CLOCK_VECTOR;

        set_vector (clock_isr, CLOCK_VECTOR, 1);

        m360.pitr |= divisor;

        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;

}