/* $Id: timer.cpp,v 1.3 2001/04/30 21:07:59 sandervl Exp $ */

/* SCCSID = %W% %E% */
/****************************************************************************
 *                                                                          *
 * Copyright (c) IBM Corporation 1994 - 1997.                               *
 *                                                                          *
 * The following IBM OS/2 source code is provided to you solely for the     *
 * the purpose of assisting you in your development of OS/2 device drivers. *
 * You may use this code in accordance with the IBM License Agreement       *
 * provided in the IBM Device Driver Source Kit for OS/2.                   *
 *                                                                          *
 ****************************************************************************/
/**@internal %W%
 *  TIMER object implementation.
 * @version %I%
 * @context
 *  Unless otherwise noted, all interfaces are Ring-0, 16-bit, kernel stack.
 *  Many of these functions run in interrupt context, this is noted in each
 *  function header.
 * @notes Suggestions for future work
 *  1.)  Should have a diagnostic in the constructor to ensure the Timer works.
 *  2.)  Should respect the Clock Select on the CS 4232.
 * @history
 */

#include <devhelp.h>
#include <include.h>
#include <string.h>			// memset()
#include "parse.h"			// fNoHWTimer
#include "irq.hpp"			// Object definition.
#include "timer.hpp"			// Object definition.
#include "midistrm.hpp"			// Object definition.

#include "tmr0_idc.h"			// IDC to TIMER0.SYS



// Enumerate the technologies from which we can generate a timer tick.
enum {  TIMER_TechNotIdentified = 0,	// Haven't yet identified the technology.
	TIMER_AdapterTimerInt,		// Adapter onboard HW timer interrupt.
	TIMER_SysTimer,			// OS/2 system timer (31 msec).
	TIMER_Timer0,			// Rudi: TIMER0 IDC
	TIMER_Timer0Fallback };		// Rudi: TIMER0 temporary unavailable


// Force use of System timer.
//int fNoHWTimer;                        // Set in parse.c when "/O:NoHWTimer"
				       // is included on DEVICE= config.sys line.

// Provide a global reference so interrupt handler can find all Timers.
PQUEUEHEAD pTimerList;


//Rudi: TIMER0
static IDCTABLE	TMR0IDCTable;


// Definitions for static data members of the Timer class.  Ref timer.hpp
// for comments on each vbl.  All these are initialized by TIMER::TIMER.

//IRQ*   TIMER::_pIRQ = 0;
USHORT TIMER::_usTimerCount;
USHORT TIMER::_usInterval_mSec;
USHORT TIMER::_usIntervalErr_uSec;
UCHAR  TIMER::_eTechnology = TIMER_TechNotIdentified;



#if 0
  // Countdown timer resolution of the CS4232, in nano-seconds.
  //### The countdown timer resolution is 9.969 uSec when C2SL = 0,
  //### and 9.92 uSec when C2SL = 1.  The C2SL can change on the fly,
  //### depending on what the Wave objects are doing.
  //### We pick a value that is about 1/2 way between the two possible
  //### actual values; introduces about a 0.25% error in actual time rates,
  //### or 1 second off after 400 seconds of play.
  //### It might be better to periodically read and respect the current
  //### value of the C2SL select register on the fly (more overhead, but
  //### more accurate timing)
  const ULONG ulCS4232_Timer_nSec = 9945;
#endif


/**@internal TIMER::_vTimerHook
 *  Handle timer tick.  Runs in Interrupt context.
 * @param None.
 * @return BOOL - TRUE if interrupt handled, FALSE otherwise.
 * @notes First checks if this interrupt was intended for us.  If using
 *  interrupt from adapter, we share this Int with Wave.  Then, if our
 *  interrupt, walks the AudioHW list looking for all Timers, and gives
 *  each instantiated timer object an opportunity to perform tasks.
 */
static void __far __loadds __saveregs TIMER::_vTimerHook(void)
{
   TIMER* pTimer;                      // Used to find Timers in AudioHW list.

   // Walk through all running timers, perform the per-tick services.
   pTimer = (TIMER*) pTimerList->Head();
   while (pTimer != NULL) {
      if ( pTimer->_eState == TIMER_Running )
	 pTimer->_vPerTickTasks();
      pTimer = (TIMER*) pTimer->pNext;
   }
}


/**@internal TIMER__iCtxHook
 *  Context hook for timer object.  Used to call the Process() method
 *  on the currently active MIDI stream.
 * @param (register EAX) - Data provided by the timer interrupt handler
 *  when the context hook is armed.  The interrupt handler should have
 *  supplied a valid stream type (ref. stream.hpp).
 * @return int 0 - per DevHelp_* definitions on Context Hook operation.
 * @notes The Context hook function is called by the OS/2 kernel out of a
 *  ring0, task context, _not_ in interrupt context.  The function is called
 *  as result of the context hook being armed.  The timer interrupt handler
 *  arms the context hook in interrupt context; this routine handles it (in
 *  task context).
 * @notes We apply the Process() method only to the 1st stream that we find;
 *  that is, we don't search for more than one active MPU or FMSYNTH stream.
 */

//Rudi: original code "forgot" to set DS !!
void __far __loadds __saveregs TIMER__iCtxHook(USHORT usStreamType);
#pragma aux TIMER__iCtxHook parm [ax];

void __far __loadds __saveregs TIMER__iCtxHook(USHORT usStreamType)
{
   MIDISTREAM* pStream;

   // The OS/2 kernel supplies us with the Ctx Hook data in the EAX
   // register.  We take advantage of this, by stuffing the stream
   // type into EAX when we arm the contex hook.  Here, we make the
   // dangerous assumption here that the compiler has not yet clobbered
   // EAX.  The _EAX() function is a pragma that we define in include.h.

   //   usStreamType = _AX();

   pStream = (MIDISTREAM*) FindActiveStream( usStreamType );

   if (pStream)   // Should always be a valid fn adr when timer is running.
      pStream->Process();
}

/**@external TIMER::TIMER
 *  Constructor for TIMER object.
 * @param IRQ* pIRQ - pointer to IRQ object, NULL if none.
 * @param USHORT uTargetMSec - target resolution in milliseconds.
 * @param USHORT usStreamType - type of MIDISTREAM that this Timer is
 *  associated with.  This param controls the stream lookup when the
 *  timer goes off.
 * @notes Constructs timer based on interrupt if possible, otherwise
 *  uses 31.25 mSec kernel timer.  The timer interrupt handler is a
 *  static function:  no matter how many Timer objects are defined, they
 *  all use the same timer interrupt handler.  The interrupt handler
 *  makes a callout to process the unique instance information of all
 *  Timer objects in existance.
 * @notes New Timer instance is added to the global AUDIOHW object list
 *  as part of its construction.
 * @notes Timer is left in TIMER_Stopped state on good creation,
 *  TIMER_Disabled state on problem.
 */
TIMER::TIMER( IRQ* pIRQ, USHORT uTargetMSec, USHORT usStreamType ) :
   _usStreamType ( usStreamType )
{
   USHORT rc;

   // Set initial state - "not functional".
   _eState = TIMER_Disabled;

   // Setup the new context hook.
   rc = DevHelp_AllocateCtxHook( (NPFN) TIMER__iCtxHook, &_ctxHookHandle );
   if (rc)
      return;

   // If this is the first Timer we've created, do the "first time only"
   // work, such as selecting the interrupt technology & programming the
   // timer interrupt.

   if (_eTechnology != TIMER_TechNotIdentified)	// Will be 0 if 1st time through.
      _eState = TIMER_Stopped;			// Not the first Timer.
   else {			// First time through, set up static vbls.

#if 0
      // Try using timer feature on the audio adapter.  The fNoHWTimer
      // flag is set from the DEVICE= config.sys linne, and can be used to
      // force system timer.
      if (! fNoHWTimer) {

	 _pIRQ = pIRQ;
	 if ( _pIRQ )
	    bGoodReturn = _pIRQ->bAddHandler( TIMER::_vTimerHook );
	 else
	    bGoodReturn = FALSE;

	 // We got an interrupt slot, now figure out the values for HW timer setup.
	 if ( bGoodReturn )
	 {
	    _usTimerCount =
	       (USHORT) (((ULONG) uTargetMSec * 1000000L) / ulCS4232_Timer_nSec);

	    // Figure out what this timer count equates to in mSec and uSec.
	    ULONG ulInterval_nSec = (((ULONG) _usTimerCount) * ulCS4232_Timer_nSec);
	    _usInterval_mSec = ulInterval_nSec / 1000000L;
	    _usIntervalErr_uSec =
	       (ulInterval_nSec - (_usInterval_mSec * 1000000L)) / 1000;
				 // Should always be positive, in range of 0..1000.

	    // All set to enable timer interrupt on the chip.  Log status.
	    //### Would be very good to check that it works, so we know to go
	    //### to alternate strategy if necessary.
	    _eTechnology = TIMER_AdapterTimerInt;
	    _eState = TIMER_Stopped;
	 }
      }

#else
      (void)pIRQ;	(void)uTargetMSec;

      if( DevHelp_AttachDD((NPSZ)"TIMER0$ ", (NPBYTE)&TMR0IDCTable) == 0 &&
			TMR0IDCTable.ProtIDCEntry && TMR0IDCTable.ProtIDC_DS ) {
	 _eTechnology = TIMER_Timer0;
	 _eState = TIMER_Stopped;
      }

#endif

      // Timer IRQ hook didn't work for some reason, use system timer.
      if ( _eState == TIMER_Disabled ) {
	 _eTechnology = TIMER_SysTimer;
	 _eState = TIMER_Stopped;
      }
   }  // End of setup for interrupt operation, executed for 1st Timer only.


   // If good creation, add Timer to global timer list & reset all time vbls.
   if ( _eState != TIMER_Disabled ) {
      _ulTime = _ulSchedTime = 0;
      _usCumulativeError = 0;
      pTimerList->PushOnTail( this );
   }

   // TIMER is in TIMER_Stopped state upon normal return, TIMER_Disabled
   // state on error.
}


/**@external TIMER::vSchedule
 *  Schedule the next Context hook invocation, 0 for next tick.
 * @param ULONG ulTime - Absolute time (mSec) at which to schedule next Ctx hook.
 * @return VOID
 * @notes
 */
VOID TIMER::vSchedule ( ULONG ulTime )
{
   cli();
   _ulSchedTime = ulTime;
   sti();
}


// Get current stream time (milliseconds).  Runs in task context.
ULONG TIMER::ulGetTime( void )
{
   ULONG ulResult;                     // Return value.

   cli();
   ulResult = _ulTime;
   sti();

   return ulResult;
}

// Set current stream time (milliseconds).  Runs in task context.
VOID TIMER::vSetTime( ULONG ulTime )
{
   cli();
   _ulTime = ulTime;
   sti();
}



/**@internal TIMER::_isAnyRunning()
 *  Predicate that determines whether any Timer is in Running state.
 * @param None.
 * @return BOOL TRUE iff at least one Timer is in Running state.
 * @notes Normally called in Task context by Start and Stop routines.
 */
static BOOL TIMER::_isAnyRunning( void )
{
   TIMER* pTimer;                      // Used to find Timers in AudioHW list.

   // Walk through all Timers, seeking one that is running.
   pTimer = (TIMER*) pTimerList->Head();
   while (pTimer != NULL) {
      if ( pTimer->_eState == TIMER_Running )
	 return TRUE;
      pTimer = (TIMER*) pTimer->pNext;
   }
   return FALSE;
}


/**@internal TIMER::_iStart
 *  Internal worker to start the timer operation.  If we have a HW timer,
 *  will start the interrupt generation.  If kernel timer, start it.
 * @param None
 * @return int 1 (Boolean TRUE) if timer starts properly
 * @return int 0 (Boolean FALSE) if problem starting timer
 * @notes Will force Ctx hook to be scheduled on next tick.
 */
int TIMER::_iStart( void )
{
   USHORT rc;

   // Disable any any pre-existing timer and reset state variables.
   if ( _eState != TIMER_Stopped )
      Stop();                          // Stop() method on this Timer.

   // _eState now equals TIMER_Stopped.

   // Reset Timer vbls & start Timer interrupt if it's not already running.
   // MMPM/2 will reset the stream time when the user rewinds, etc.

   _ulSchedTime = 0;                   // Force arming ctx hook on next tick.
   _usCumulativeError = 0;              // Zero out any fractional time.

   if ( _isAnyRunning() )		// If timer hardware already running
      _eState = TIMER_Running;		// Then just flip our state.
   else {				// Otherwise start interrupts.
      switch ( _eTechnology ) {
#if 0
      case TIMER_AdapterTimerInt:
	 bGoodReturn = _pIRQ->bEnableHandler( TIMER::_vTimerHook );
	   /*** Our ISR can be called at any point after this, so all our state
	    * variables must be consistent.  Even though we haven't enabled
	    * the Timer on the chip, we could get an Int from Wave operations
	    * (which should be ignored).
	    */
	 // Everything is setup for the interrupt, now enable it on the chip.
	 if (bGoodReturn) {
	    _vStartHWTicks();
	    _eState = TIMER_Running;
	 }
	 break;
#endif

      case TIMER_Timer0:
	 _usInterval_mSec = 4;
	 _usIntervalErr_uSec = 0;

	 rc = (*(PTMRFN)TMR0IDCTable.ProtIDCEntry)
			(TMR0_REG, (ULONG)TIMER::_vTimerHook, _usInterval_mSec);
	 if (! rc) {
	    _eState = TIMER_Running;
	    break;
	 }

	 _eTechnology = TIMER_Timer0Fallback;

      case TIMER_SysTimer:
	 _usInterval_mSec = 31;
	 _usIntervalErr_uSec = 250;

	 rc = DevHelp_SetTimer( (NPFN) TIMER::_vTimerHook );
	 if (! rc)
	    _eState = TIMER_Running;
	 break;
      }
   }

   if ( _eState != TIMER_Running ) {   // Set error condition & log problem.
      _eState = TIMER_Disabled;
      return 0;
   }

   return 1;
}


/**@internal TIMER::_iStop
 *  Internal worker to shutdown the timer interrupt and the timer clock.
 * @param None.
 * @return int 0.
 * @notes Will not destroy "next scheduled ctx hook" information.
 * @notes Leaves timer in TIMER_Stopped state.  Timer interrupts are stopped
 *  as well if no other Timer is running.
 */
int TIMER::_iStop( void )
{
   _eState = TIMER_Stopped;		// Stop this Timer.

   if (!_isAnyRunning()) {		// If no other Timers are running...
      switch( _eTechnology ) {		// Then shutdown the interrupt.
#if	0
      case TIMER_AdapterTimerInt:
	 // Disable the interrupt on the chip and in the IRQ object.
	 _vStopHWTicks();
	 break;
#endif

      case TIMER_Timer0Fallback:
	_eTechnology = TIMER_Timer0;
      case TIMER_SysTimer:
	 DevHelp_ResetTimer( (NPFN) TIMER::_vTimerHook );
	 break;

      case TIMER_Timer0:
	 (*(PTMRFN)TMR0IDCTable.ProtIDCEntry)
			(TMR0_DEREG, (ULONG)TIMER::_vTimerHook, 0);
	 break;
      }
   }

   return 0;
}


// Perform the per tick, per timer object tasks:  maintain time,
// arm a context hook if it's time to run the MIDI parser.  Runs
// in interrupt context.
VOID TIMER::_vPerTickTasks( void )
{
   USHORT uMSec;

   if ( _eState == TIMER_Running ) {
      // Update our clock.
      uMSec = _usInterval_mSec;
      _usCumulativeError += _usIntervalErr_uSec;
      if (_usCumulativeError >= 1000) {
	 _usCumulativeError -= 1000;
	 ++uMSec;
      }
      _ulTime += uMSec;

      // Set the context hook if it's time.
      if ((_ulSchedTime == 0) || (_ulTime >= _ulSchedTime))
      {
	 // Arm ctx hook, pass stream type to the ctx hook handler.
	 DevHelp_ArmCtxHook( _usStreamType, _ctxHookHandle );
	 _ulSchedTime = (ULONG)-1;
      }
   }
}

#if	0

// Start the generation of HW timer ticks on the chip.
static VOID TIMER::_vStartHWTicks( void )
{
}


// Start the generation of HW timer ticks on the chip.
static VOID TIMER::_vStopHWTicks( void )
{
}

#endif