Subversion Repositories openrisc_2011-10-31

/*  Clock

 *

 *  This routine initializes the interval timer on the

 *  PA-RISC CPU.  The tick frequency is specified by the bsp.

 *

 *  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.

 *

 *  $Id: clock.c,v 1.2 2001-09-27 12:01:20 chris Exp $

 */

#include <rtems.h>

#include <rtems/libio.h>

/* should get this from bsp.h, but it is not installed yet */

rtems_isr_entry set_vector(rtems_isr_entry, rtems_vector_number, int);

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

typedef unsigned long long hppa_click_count_t;

/*

 * These are set by clock driver during its init

 */

rtems_device_major_number rtems_clock_major = ~0;

rtems_device_minor_number rtems_clock_minor;

/*

 * CPU_HPPA_CLICKS_PER_TICK is either a #define or an rtems_unsigned32

 *   allocated and set by bsp_start()

 */

#ifndef CPU_HPPA_CLICKS_PER_TICK

extern rtems_unsigned32 CPU_HPPA_CLICKS_PER_TICK;

#endif

volatile rtems_unsigned32 Clock_driver_ticks;

rtems_unsigned32 Clock_isrs;              /* ISRs until next tick */

rtems_unsigned32   most_recent_itimer_value;

rtems_unsigned64   Clock_clicks;        /* running total of cycles */

rtems_unsigned32   Clock_clicks_interrupt;

void  Clock_exit(void);

void

ReInstall_clock(rtems_isr_entry new_clock_isr)

{

    rtems_unsigned32 isrlevel = 0;

    rtems_interrupt_disable(isrlevel);

    (void) set_vector(

      new_clock_isr,

      HPPA_INTERRUPT_EXTERNAL_INTERVAL_TIMER,

      1

    );

    rtems_interrupt_enable(isrlevel);

}

/*

 * read itimer and update Clock_clicks as appropriate

 */

rtems_unsigned32

Clock_read_itimer()

{

    rtems_unsigned32 isrlevel;

    rtems_unsigned32 itimer_value;

    rtems_unsigned32 wrap_count;

    rtems_unsigned32 recent_count;

    rtems_interrupt_disable(isrlevel);

    wrap_count = (Clock_clicks & 0xFFFFFFFF00000000ULL) >> 32;

    recent_count = (rtems_unsigned32) Clock_clicks;

    itimer_value = get_itimer();

    if (itimer_value < recent_count)

        wrap_count++;

    Clock_clicks = (((rtems_unsigned64) wrap_count) << 32) + itimer_value;

    rtems_interrupt_enable(isrlevel);

    return itimer_value;

}

void Install_clock(rtems_isr_entry clock_isr)

{

    Clock_driver_ticks = 0;

    Clock_clicks_interrupt = 0;

    Clock_clicks = 0;

    Clock_isrs = rtems_configuration_get_milliseconds_per_tick();

    /*

     * initialize the interval here

     * First tick is set to right amount of time in the future

     * Future ticks will be incremented over last value set

     * in order to provide consistent clicks in the face of

     * interrupt overhead

     */

    Clock_clicks_interrupt = Clock_read_itimer() + CPU_HPPA_CLICKS_PER_TICK;

    set_itimer((rtems_unsigned32) Clock_clicks_interrupt);

    (void) set_vector(clock_isr, HPPA_INTERRUPT_EXTERNAL_INTERVAL_TIMER, 1);

    atexit(Clock_exit);

}

rtems_isr

Clock_isr(rtems_vector_number vector)

{

    rtems_unsigned32 clicks_til_next_interrupt;

    rtems_unsigned32 itimer_value;

    /*

     * setup for next interrupt; making sure the new value is reasonably

     * in the future.... in case we lost out on an interrupt somehow

     */

    itimer_value = Clock_read_itimer();

    Clock_clicks_interrupt += CPU_HPPA_CLICKS_PER_TICK;

    /*

     * how far away is next interrupt *really*

     * It may be a long time; this subtraction works even if

     * Clock_clicks_interrupt < Clock_clicks_low_order via

     * the miracle of unsigned math.

     */

    clicks_til_next_interrupt = Clock_clicks_interrupt - itimer_value;

    /*

     * If it is too soon then bump it up.

     * This should only happen if CPU_HPPA_CLICKS_PER_TICK is too small.

     * But setting it low is useful for debug, so...

     */

    if (clicks_til_next_interrupt < 400)

    {

        Clock_clicks_interrupt = itimer_value + 1000;

        /* XXX: count these! this should be rare */

    }

    /*

     * If it is too late, that means we missed the interrupt somehow.

     * Rather than wait 35-50s for a wrap, we just fudge it here.

     */

    if (clicks_til_next_interrupt > CPU_HPPA_CLICKS_PER_TICK)

    {

        Clock_clicks_interrupt = itimer_value + 1000;

        /* XXX: count these! this should never happen :-) */

    }

    set_itimer((rtems_unsigned32) Clock_clicks_interrupt);

    Clock_driver_ticks++;

    if (Clock_isrs == 1)

    {

        rtems_clock_tick();

        Clock_isrs = rtems_configuration_get_milliseconds_per_tick();

        if (Clock_isrs == 0)

            Clock_isrs = 1;

    }

    else

        Clock_isrs--;

}

/*

 * Called via atexit()

 * Remove the clock interrupt handler by setting handler to NULL

 */

void

Clock_exit(void)

{

  (void) set_vector(0, HPPA_INTERRUPT_EXTERNAL_INTERVAL_TIMER, 1);

}

/*

 * spin delay for specified number of microseconds

 * used by RTEMS delay macro

 */

void

Clock_delay(rtems_unsigned32 microseconds)

{

    rtems_unsigned64 future_time;

    (void) Clock_read_itimer();

    future_time = Clock_clicks +

      ((rtems_unsigned64) microseconds) *

        rtems_cpu_configuration_get_itimer_clicks_per_microsecond();

    for (;;)

    {

        (void) Clock_read_itimer();

        if (future_time <= Clock_clicks)

            break;

    }

}

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_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(HPPA_INTERRUPT_EXTERNAL_INTERVAL_TIMER);

    }

    else if (args->command == rtems_build_name('N', 'E', 'W', ' '))

    {

        ReInstall_clock(args->buffer);

    }

done:

    return RTEMS_SUCCESSFUL;

}