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/*

(C) Copyright IBM Corp. 2008

All rights reserved.

Redistribution and use in source and binary forms, with or without

modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice,

this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright

notice, this list of conditions and the following disclaimer in the

documentation and/or other materials provided with the distribution.

* Neither the name of IBM nor the names of its contributors may be

used to endorse or promote products derived from this software without

specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

POSSIBILITY OF SUCH DAMAGE.

*/

/* Second Level Interrupt handler and related services for SPU timers.  */

#include "spu_timer_internal.h"

/* Resets decrementer to the specified value. Also updates software timebase

   to account for the time between the last decrementer reset and now. There

   are two cases:

    * Called by application to start a new timer.

    * Called by spu_clock to active the next timer.

   In both cases, the amount of time is the current interval timeout minus the

   current decrementer value.  */

void

__reset_spu_decr (int val)

{

  /* The interrupt occurs when the msb goes from 0 to 1 or when the decrementer

     goes from 0 to -1.  To be precisely accurate we should set the timer to

     the intverval -1, unless the interval passed in is 0 in which case it

     should be left at 0.  */

  int enable_val = (__likely (val)) ? val - 1 : 0;

  /* Decrementer must be stopped before writing it - minimize the time

     stopped.  */

  unsigned mask = __disable_spu_decr ();

  /* Perform tb correction before resettting the decrementer. the corrected

     value is the current timeout value minus the current decrementer value.

     Occasionally the read returns 0 - a second read will clear this

     condition.  */

  spu_readch (SPU_RdDec);

  int decval = spu_readch (SPU_RdDec);

  /* Restart decrementer with next timeout val.  */

  __enable_spu_decr (enable_val, mask);

  /* Update the timebase values before enabling for interrupts.  */

  __spu_tb_val += __spu_tb_timeout - decval;

  __spu_tb_timeout = enable_val;

}

/* Update software timebase and timeout value for the 'next to expire' timer.

   Called when starting a new timer so the timer list will have timeouts

   relative to the current time.  */

static inline void

__update_spu_tb_val (void)

{

  int elapsed = __spu_tb_timeout - spu_readch (SPU_RdDec);

#ifdef SPU_TIMER_DEBUG

  if (elapsed < 0)

    ABORT ();

#endif

  __spu_tb_val += elapsed;

  /* Adjust the timeout for the timer next to expire. Note this could cause

     the timeout to go negative, if it was just about to expire when we called

     spu_timer_start.  This is OK, since this can happen any time interrupts

     are disabled. We just schedule an immediate timeout in this case.  */

  if (__spu_timers_active)

    {

      __spu_timers_active->tmout -= elapsed;

      if (__spu_timers_active->tmout < 0)

        __spu_timers_active->tmout = 0;

    }

}

/* Add an allocated timer to the active list. The active list is sorted by

   timeout value. The timer at the head of the list is the timer that will

   expire next.  The rest of the timers have a timeout value that is relative

   to the timer ahead of it on the list.  This relative value is determined

   here, when the timer is added to the active list. When its position in the

   list is found, the timer's timeout value is set to its interval minus the

   sum of all the timeout values ahead of it.  The timeout value for the timer

   following the newly added timer is then adjusted to a new relative value. If

   the newly added timer is at the head of the list, the decrementer is reset.

   This function is called by SLIH to restart multiple timers (reset == 0) or

   by spu_timer_start() to start a single timer (reset == 1).  */

void

__spu_timer_start (int id, int reset)

{

  spu_timer_t *t;

  spu_timer_t **pn;

  spu_timer_t *start = &__spu_timers[id];

  unsigned tmout_time = 0;

  unsigned my_intvl = start->intvl;

  unsigned was_enabled = spu_readch (SPU_RdMachStat) & 0x1;

  spu_idisable ();

  t = __spu_timers_active;

  pn = &__spu_timers_active;

  /* If the active list is empty, just add the timer with the timeout set to

     the interval. Otherwise find the place in the list for the timer, setting

     its timeout to its interval minus the sum of timeouts ahead of it.  */

  start->state = SPU_TIMER_ACTIVE;

  if (__likely (!t))

    {

      __spu_timers_active = start;

      start->next = NULL;

      start->tmout = my_intvl;

    }

  else

    {

      /* Update swtb and timeout val of the next timer, so all times are

         relative to now.  */

      if (reset)

        __update_spu_tb_val ();

      while (t && (my_intvl >= (tmout_time + t->tmout)))

        {

          tmout_time += t->tmout;

          pn = &t->next;;

          t = t->next;

        }

      start->next = t;

      start->tmout = my_intvl - tmout_time;

      *pn = start;

      /* Adjust timeout for timer after us.  */

      if (t)

        t->tmout -= start->tmout;

    }

  if (reset && (__spu_timers_active == start))

    __reset_spu_decr (__spu_timers_active->tmout);

  if (__unlikely (was_enabled))

    spu_ienable ();

}

/* SLIH for decrementer.  Manages software timebase and timers.

   Called by SPU FLIH. Assumes decrementer is still running

   (event not yet acknowledeged).  */

unsigned int

spu_clock_slih (unsigned status)

{

  int decr_reset_val;

  spu_timer_t *active, *handled;

  unsigned was_enabled = spu_readch (SPU_RdMachStat) & 0x1;

  status &= ~MFC_DECREMENTER_EVENT;

  spu_idisable ();

  /* The decrementer has now expired.  The decrementer event was acknowledged

     in the FLIH but not disabled. The decrementer will continue to run while

     we're running the clock/timer handler. The software clock keeps running,

     and accounts for all the time spent running handlers. Add the current

     timeout to the software timebase and set the timeout to DECR_MAX. This

     allows the "clock read" code to continue to work while we're in here, and

     gives us the most possible time to finish before another underflow.  */

  __spu_tb_val += __spu_tb_timeout;

  __spu_tb_timeout = DECR_MAX;

  /* For all timers that have the current timeout value, move them from the

     active list to the handled list and call their handlers. Note that the

     handled/stopped lists may be manipulated by the handlers if they wish to

     stop/free the timers. Note that only the first expired timer will reflect

     the real timeout value; the rest of the timers that had the same timeout

     value will have a relative value of zero.  */

  if (__spu_timers_active)

    {

      __spu_timers_active->tmout = 0;

      while ((active = __spu_timers_active)

             && (active->tmout <= TIMER_INTERVAL_WINDOW))

        {

          __spu_timers_active = active->next;

          active->next = __spu_timers_handled;

          __spu_timers_handled = active;

          active->state = SPU_TIMER_HANDLED;

          (*active->func) (active->id);

        }

    }

  /* put the handled timers back on the list and restart decrementer.  */

  while ((handled = __spu_timers_handled) != NULL)

    {

      __spu_timers_handled = handled->next;

      __spu_timer_start (handled->id, 0);

    }

  /* Reset the decrementer before returning. If we have any active timers, we

     set it to the timeout value for the timer at the head of the list, else

     the default clock value.  */

  decr_reset_val = __spu_timers_active ? __spu_timers_active->tmout : CLOCK_START_VALUE;

  __reset_spu_decr (decr_reset_val);

  if (__likely (was_enabled))

    spu_ienable ();

  return status;

}