/*****************************************************************************

        Copyright 1994 MOTOROLA, INC.  All Rights Reserved.  This file
        contains copyrighted material.  Use of this file is restricted
        by the provisions of a Motorola Software License Agreement.

Copyright (c) 1996  International Business Machines Corporation

Module Name:

    PXCLOCK.C

Abstract:

    This module contains the system clock interrupt handler.
    The DECREMENTER is used to implement the system clock.  The
    handler resets the DECREMENTER to SYSTEM_TIME (accounting
    for interrupt latency), and updates the system time.


Author:

    Steve Johns  10-Feb-1994

Revision History:

******************************************************************************/

#include "halp.h"

extern ULONG HalpPerformanceFrequency;

BOOLEAN
KdPollBreakIn (
    VOID
    );

ULONG HalpClockCount;
ULONG HalpFullTickClockCount;
ULONG HalpUpdateDecrementer();

ULONG HalpCurrentTimeIncrement;
ULONG HalpNextIntervalCount;
ULONG HalpNewTimeIncrement;

#if defined(SOFT_HDD_LAMP)

extern HDD_LAMP_STATUS HalpHddLamp;

#endif

BOOLEAN
HalpHandleDecrementerInterrupt(
    IN PKINTERRUPT Interrupt,
    IN PVOID ServiceContext,
    IN PVOID TrapFrame
    )

/*++

Routine Description:

    Clock interrupt handler for processor 0.

Arguments:

    Interrupt

    ServiceContext

    TrapFrame

Return Value:

    TRUE

--*/
{
     KIRQL OldIrql;

     //
     // Raise irql via updating the PCR
     //

     OldIrql = PCR->CurrentIrql;

     PCR->CurrentIrql = CLOCK2_LEVEL;

     //
     // Reset DECREMENTER, accounting for interrupt latency.
     //

     HalpUpdateDecrementer(HalpClockCount);

     //
     // Call the kernel to update system time
     //

     KeUpdateSystemTime(TrapFrame,HalpCurrentTimeIncrement);

     HalpCurrentTimeIncrement = HalpNewTimeIncrement;

#if defined(SOFT_HDD_LAMP)

     //
     // If HDD Lamp is on and there have been no new interrupts for
     // mass storage interrupts for enough ticks that the count has
     // gone zero, turn it off.
     //

     if ( HalpHddLamp.Count > 0 ) {
         if ( --HalpHddLamp.Count == 0 ) {
             *(PUCHAR)((PUCHAR)HalpIoControlBase + HDD_LAMP_PORT) = 0;
         }
     }

#endif

     //
     // Lower Irql to original value and enable interrupts
     //

     PCR->CurrentIrql = OldIrql;

#if defined(WOODFIELD)

     //
     // added read to initiate a PCI I/O cycle in order to work around
     // woodfield prime SIO DMA bug
     //

     {
       volatile UCHAR DataByte;
       DataByte = READ_REGISTER_UCHAR((PUCHAR)HalpIoControlBase + 0xcf8);
     }

#endif

     HalpEnableInterrupts();

     if ( KdDebuggerEnabled && KdPollBreakIn() ) {
       DbgBreakPointWithStatus(DBG_STATUS_CONTROL_C);
     }

     return (TRUE);
}


#if defined(_MP_PPC_)

BOOLEAN
HalpHandleDecrementerInterrupt1(
    IN PKINTERRUPT Interrupt,
    IN PVOID ServiceContext,
    IN PVOID TrapFrame
    )

/*++

Routine Description:

    Clock interrupt handler for processors other than 0.

Arguments:

    Interrupt

    ServiceContext

    TrapFrame

Return Value:

    TRUE

--*/
{

     KIRQL OldIrql;

     //
     // Raise irql via updating the PCR
     //

     OldIrql = PCR->CurrentIrql;

     PCR->CurrentIrql = CLOCK2_LEVEL;

     //
     // Reset DECREMENTER, accounting for interrupt latency.
     //

     HalpUpdateDecrementer(HalpFullTickClockCount);

     //
     // Call the kernel to update run time for this thread and process.
     //

     KeUpdateRunTime(TrapFrame);

     //
     // Lower Irql to original value
     //

     PCR->CurrentIrql = OldIrql;

     return TRUE;
}

#endif


ULONG
HalSetTimeIncrement (
    IN ULONG DesiredIncrement
    )

/*++

Routine Description:

    This function is called to set the clock interrupt rate to the frequency
    required by the specified time increment value.

    N.B. This function is only executed on the processor that keeps the
         system time.

Arguments:

    DesiredIncrement - Supplies desired number of 100ns units between clock
        interrupts.

Return Value:

    The actual time increment in 100ns units.

--*/

{

    ULONG NewTimeIncrement;
    ULONG NextIntervalCount;
    KIRQL OldIrql;

    //
    // Raise IRQL to the highest level, set the new clock interrupt
    // parameters, lower IRQl, and return the new time increment value.
    //


    KeRaiseIrql(HIGH_LEVEL, &OldIrql);

    //
    // HalpPerformanceFrequence is the number of times the decrementer
    // ticks in 1 second.  MINIMUM_INCREMENT is the number of 100 is the
    // number of 100ns units in 1 ms.
    // Therefore, DesiredIncrement/MINUMUM_INCREMENT is the number of
    // ms desired.  This multiplied by the number of decrementer ticks
    // in 1 second, divided by 1000 gives the number of ticks in the
    // desired number of milliseconds.  This value will go into the
    // decrementer.
    //

    NextIntervalCount = (HalpPerformanceFrequency *
                           (DesiredIncrement/MINIMUM_INCREMENT)) / 1000;

    //
    // Calculate the number of 100ns units to report to the kernel every
    // time the decrementer fires with this new period.  Note, for small
    // values of DesiredIncrement (min being 10000, ie 1ms), truncation
    // in the above may result in a small decrement in the 5th decimal
    // place.  As we are effectively dealing with a 4 digit number, eg
    // 10000 becomes 9999.something, we really can't do any better than
    // the following.
    //

    NewTimeIncrement = DesiredIncrement/MINIMUM_INCREMENT * MINIMUM_INCREMENT;
    HalpClockCount = NextIntervalCount;
    HalpNewTimeIncrement = NewTimeIncrement;
    KeLowerIrql(OldIrql);
    return NewTimeIncrement;
}