source: rtems/c/src/lib/libcpu/hppa1.1/clock/clock.c @ ac7d5ef0

/*  Clock
 *
 *  This routine initializes the interval timer on the
 *  PA-RISC CPU.  The tick frequency is specified by the bsp.
 *
 *  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.
 *
 *  $Id$
 */

#include <bsp.h>
#include <clockdrv.h>

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

extern rtems_cpu_table           Cpu_table;             /* owned by BSP */

typedef unsigned long long hppa_click_count_t;

/*
 * 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;

rtems_device_driver Clock_initialize(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void *pargp,
  rtems_id tid,
  rtems_unsigned32 *rval
)
{
    Install_clock(Clock_isr);
}

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 = BSP_Configuration.microseconds_per_tick / 1000;

    if (BSP_Configuration.ticks_per_timeslice)
    {
        /*
         * 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 = BSP_Configuration.microseconds_per_tick / 10000;
        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)
{
    if ( BSP_Configuration.ticks_per_timeslice )
    {
        (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) *
        Cpu_table.itimer_clicks_per_microsecond;

    for (;;)
    {
        (void) Clock_read_itimer();
        if (future_time <= Clock_clicks)
            break;
    }
}