xref: /gem5/src/dev/intel_8254_timer.cc

/*
 * Copyright (c) 2004, 2005
 * The Regents of The University of Michigan
 * All Rights Reserved
 *
 * This code is part of the M5 simulator.
 *
 * Permission is granted to use, copy, create derivative works and
 * redistribute this software and such derivative works for any
 * purpose, so long as the copyright notice above, this grant of
 * permission, and the disclaimer below appear in all copies made; and
 * so long as the name of The University of Michigan is not used in
 * any advertising or publicity pertaining to the use or distribution
 * of this software without specific, written prior authorization.
 *
 * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION FROM THE
 * UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY PURPOSE, AND
 * WITHOUT WARRANTY BY THE UNIVERSITY OF MICHIGAN OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE. THE REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE
 * LIABLE FOR ANY DAMAGES, INCLUDING DIRECT, SPECIAL, INDIRECT,
 * INCIDENTAL, OR CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM
 * ARISING OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
 * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGES.
 *
 * Authors: Ali G. Saidi
 *          Andrew L. Schultz
 *          Miguel J. Serrano
 */

#include "base/misc.hh"
#include "dev/intel_8254_timer.hh"

using namespace std;

Intel8254Timer::Intel8254Timer(const string &name)
    : _name(name), counter0(name + ".counter0"), counter1(name + ".counter1"),
      counter2(name + ".counter2")
{
    counter[0] = &counter0;
    counter[1] = &counter0;
    counter[2] = &counter0;
}

void
Intel8254Timer::writeControl(const CtrlReg data)
{
    int sel = data.sel;

    if (sel == ReadBackCommand)
       panic("PITimer Read-Back Command is not implemented.\n");

    if (data.rw == LatchCommand)
        counter[sel]->latchCount();
    else {
        counter[sel]->setRW(data.rw);
        counter[sel]->setMode(data.mode);
        counter[sel]->setBCD(data.bcd);
    }
}

void
Intel8254Timer::serialize(const string &base, ostream &os)
{
    // serialize the counters
    counter0.serialize(base + ".counter0", os);
    counter1.serialize(base + ".counter1", os);
    counter2.serialize(base + ".counter2", os);
}

void
Intel8254Timer::unserialize(const string &base, Checkpoint *cp,
        const string &section)
{
    // unserialze the counters
    counter0.unserialize(base + ".counter0", cp, section);
    counter1.unserialize(base + ".counter1", cp, section);
    counter2.unserialize(base + ".counter2", cp, section);
}

Intel8254Timer::Counter::Counter(const string &name)
    : _name(name), event(this), count(0), latched_count(0), period(0),
      mode(0), output_high(false), latch_on(false), read_byte(LSB),
      write_byte(LSB)
{

}

void
Intel8254Timer::Counter::latchCount()
{
    // behave like a real latch
    if(!latch_on) {
        latch_on = true;
        read_byte = LSB;
        latched_count = count;
    }
}

uint8_t
Intel8254Timer::Counter::read()
{
    if (latch_on) {
        switch (read_byte) {
          case LSB:
            read_byte = MSB;
            return (uint8_t)latched_count;
            break;
          case MSB:
            read_byte = LSB;
            latch_on = false;
            return latched_count >> 8;
            break;
          default:
            panic("Shouldn't be here");
        }
    } else {
        switch (read_byte) {
          case LSB:
            read_byte = MSB;
            return (uint8_t)count;
            break;
          case MSB:
            read_byte = LSB;
            return count >> 8;
            break;
          default:
            panic("Shouldn't be here");
        }
    }
}

void
Intel8254Timer::Counter::write(const uint8_t data)
{
    switch (write_byte) {
      case LSB:
        count = (count & 0xFF00) | data;

        if (event.scheduled())
          event.deschedule();
        output_high = false;
        write_byte = MSB;
        break;

      case MSB:
        count = (count & 0x00FF) | (data << 8);
        // In the RateGen or SquareWave modes, the timer wraps around and
        // triggers on a value of 1, not 0.
        if (mode == RateGen || mode == SquareWave)
            period = count - 1;
        else
            period = count;

        if (period > 0)
            event.setTo(period);

        write_byte = LSB;
        break;
    }
}

void
Intel8254Timer::Counter::setRW(int rw_val)
{
    if (rw_val != TwoPhase)
        panic("Only LSB/MSB read/write is implemented.\n");
}

void
Intel8254Timer::Counter::setMode(int mode_val)
{
    if(mode_val != InitTc && mode_val != RateGen &&
       mode_val != SquareWave)
        panic("PIT mode %#x is not implemented: \n", mode_val);

    mode = mode_val;
}

void
Intel8254Timer::Counter::setBCD(int bcd_val)
{
    if (bcd_val)
        panic("PITimer does not implement BCD counts.\n");
}

bool
Intel8254Timer::Counter::outputHigh()
{
    return output_high;
}

void
Intel8254Timer::Counter::serialize(const string &base, ostream &os)
{
    paramOut(os, base + ".count", count);
    paramOut(os, base + ".latched_count", latched_count);
    paramOut(os, base + ".period", period);
    paramOut(os, base + ".mode", mode);
    paramOut(os, base + ".output_high", output_high);
    paramOut(os, base + ".latch_on", latch_on);
    paramOut(os, base + ".read_byte", read_byte);
    paramOut(os, base + ".write_byte", write_byte);

    Tick event_tick = 0;
    if (event.scheduled())
        event_tick = event.when();
    paramOut(os, base + ".event_tick", event_tick);
}

void
Intel8254Timer::Counter::unserialize(const string &base, Checkpoint *cp,
                                         const string &section)
{
    paramIn(cp, section, base + ".count", count);
    paramIn(cp, section, base + ".latched_count", latched_count);
    paramIn(cp, section, base + ".period", period);
    paramIn(cp, section, base + ".mode", mode);
    paramIn(cp, section, base + ".output_high", output_high);
    paramIn(cp, section, base + ".latch_on", latch_on);
    paramIn(cp, section, base + ".read_byte", read_byte);
    paramIn(cp, section, base + ".write_byte", write_byte);

    Tick event_tick;
    paramIn(cp, section, base + ".event_tick", event_tick);
    if (event_tick)
        event.schedule(event_tick);
}

Intel8254Timer::Counter::CounterEvent::CounterEvent(Counter* c_ptr)
    : Event(&mainEventQueue)
{
    interval = (Tick)(Clock::Float::s / 1193180.0);
    counter = c_ptr;
}

void
Intel8254Timer::Counter::CounterEvent::process()
{
    DPRINTF(Intel8254Timer, "Timer Interrupt\n");
    switch (counter->mode) {
      case InitTc:
        counter->output_high = true;
        break;
      case RateGen:
      case SquareWave:
        setTo(counter->period);
        break;
      default:
        panic("Unimplemented PITimer mode.\n");
    }
}

void
Intel8254Timer::Counter::CounterEvent::setTo(int clocks)
{
    if (clocks == 0)
        panic("Timer can't be set to go off instantly.\n");
    DPRINTF(Intel8254Timer, "Timer set to curTick + %d\n",
            clocks * interval);
    schedule(curTick + clocks * interval);
}

const char *
Intel8254Timer::Counter::CounterEvent::description() const
{
    return "tsunami 8254 Interval timer";
}