gem5/src/dev/dma_device.cc

/*
 * Copyright (c) 2012, 2015, 2017, 2019 ARM Limited
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 * Copyright (c) 2006 The Regents of The University of Michigan
 * All rights reserved.
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#include "dev/dma_device.hh"

#include <utility>

#include "base/chunk_generator.hh"
#include "debug/DMA.hh"
#include "debug/Drain.hh"
#include "sim/clocked_object.hh"
#include "sim/system.hh"

DmaPort::DmaPort(ClockedObject *dev, System *s,
                 uint32_t sid, uint32_t ssid)
    : RequestPort(dev->name() + ".dma", dev),
      device(dev), sys(s), requestorId(s->getRequestorId(dev)),
      sendEvent([this]{ sendDma(); }, dev->name()),
      defaultSid(sid), defaultSSid(ssid), cacheLineSize(s->cacheLineSize())
{ }

void
DmaPort::handleResp(PacketPtr pkt, Tick delay)
{
    // should always see a response with a sender state
    assert(pkt->isResponse());

    // get the DMA sender state
    auto *state = dynamic_cast<DmaReqState*>(pkt->senderState);
    assert(state);

    DPRINTF(DMA, "Received response %s for addr: %#x size: %d nb: %d,"  \
            " tot: %d sched %d\n",
            pkt->cmdString(), pkt->getAddr(), pkt->req->getSize(),
            state->numBytes, state->totBytes,
            state->completionEvent ?
            state->completionEvent->scheduled() : 0);

    assert(pendingCount != 0);
    pendingCount--;

    // update the number of bytes received based on the request rather
    // than the packet as the latter could be rounded up to line sizes
    state->numBytes += pkt->req->getSize();
    assert(state->totBytes >= state->numBytes);

    // if we have reached the total number of bytes for this DMA
    // request, then signal the completion and delete the sate
    if (state->totBytes == state->numBytes) {
        if (state->completionEvent) {
            delay += state->delay;
            device->schedule(state->completionEvent, curTick() + delay);
        }
        delete state;
    }

    // delete the packet
    delete pkt;

    // we might be drained at this point, if so signal the drain event
    if (pendingCount == 0)
        signalDrainDone();
}

bool
DmaPort::recvTimingResp(PacketPtr pkt)
{
    // We shouldn't ever get a cacheable block in Modified state
    assert(pkt->req->isUncacheable() ||
           !(pkt->cacheResponding() && !pkt->hasSharers()));

    handleResp(pkt);

    return true;
}

DmaDevice::DmaDevice(const Params &p)
    : PioDevice(p), dmaPort(this, sys, p.sid, p.ssid)
{ }

void
DmaDevice::init()
{
    panic_if(!dmaPort.isConnected(),
             "DMA port of %s not connected to anything!", name());
    PioDevice::init();
}

DrainState
DmaPort::drain()
{
    if (pendingCount == 0) {
        return DrainState::Drained;
    } else {
        DPRINTF(Drain, "DmaPort not drained\n");
        return DrainState::Draining;
    }
}

void
DmaPort::recvReqRetry()
{
    assert(transmitList.size());
    trySendTimingReq();
}

void
DmaPort::dmaAction(Packet::Command cmd, Addr addr, int size, Event *event,
                   uint8_t *data, uint32_t sid, uint32_t ssid, Tick delay,
                   Request::Flags flag)
{
    // one DMA request sender state for every action, that is then
    // split into many requests and packets based on the block size,
    // i.e. cache line size
    DmaReqState *reqState = new DmaReqState(event, size, delay);

    RequestPtr req = nullptr;

    DPRINTF(DMA, "Starting DMA for addr: %#x size: %d sched: %d\n", addr, size,
            event ? event->scheduled() : -1);
    for (ChunkGenerator gen(addr, size, cacheLineSize);
         !gen.done(); gen.next()) {

        req = std::make_shared<Request>(
            gen.addr(), gen.size(), flag, requestorId);

        req->setStreamId(sid);
        req->setSubstreamId(ssid);

        req->taskId(ContextSwitchTaskId::DMA);
        PacketPtr pkt = new Packet(req, cmd);

        // Increment the data pointer on a write
        if (data)
            pkt->dataStatic(data + gen.complete());

        pkt->senderState = reqState;

        DPRINTF(DMA, "--Queuing DMA for addr: %#x size: %d\n", gen.addr(),
                gen.size());
        queueDma(pkt);
    }

    // in zero time also initiate the sending of the packets we have
    // just created, for atomic this involves actually completing all
    // the requests
    sendDma();
}

void
DmaPort::dmaAction(Packet::Command cmd, Addr addr, int size, Event *event,
                   uint8_t *data, Tick delay, Request::Flags flag)
{
    dmaAction(cmd, addr, size, event, data,
              defaultSid, defaultSSid, delay, flag);
}

void
DmaPort::queueDma(PacketPtr pkt)
{
    transmitList.push_back(pkt);

    // remember that we have another packet pending, this will only be
    // decremented once a response comes back
    pendingCount++;
}

void
DmaPort::trySendTimingReq()
{
    // send the first packet on the transmit list and schedule the
    // following send if it is successful
    PacketPtr pkt = transmitList.front();

    DPRINTF(DMA, "Trying to send %s addr %#x\n", pkt->cmdString(),
            pkt->getAddr());

    inRetry = !sendTimingReq(pkt);
    if (!inRetry) {
        transmitList.pop_front();
        DPRINTF(DMA, "-- Done\n");
        // if there is more to do, then do so
        if (!transmitList.empty())
            // this should ultimately wait for as many cycles as the
            // device needs to send the packet, but currently the port
            // does not have any known width so simply wait a single
            // cycle
            device->schedule(sendEvent, device->clockEdge(Cycles(1)));
    } else {
        DPRINTF(DMA, "-- Failed, waiting for retry\n");
    }

    DPRINTF(DMA, "TransmitList: %d, inRetry: %d\n",
            transmitList.size(), inRetry);
}

void
DmaPort::sendDma()
{
    // some kind of selcetion between access methods
    // more work is going to have to be done to make
    // switching actually work
    assert(transmitList.size());

    if (sys->isTimingMode()) {
        // if we are either waiting for a retry or are still waiting
        // after sending the last packet, then do not proceed
        if (inRetry || sendEvent.scheduled()) {
            DPRINTF(DMA, "Can't send immediately, waiting to send\n");
            return;
        }

        trySendTimingReq();
    } else if (sys->isAtomicMode()) {
        // send everything there is to send in zero time
        while (!transmitList.empty()) {
            PacketPtr pkt = transmitList.front();
            transmitList.pop_front();

            DPRINTF(DMA, "Sending  DMA for addr: %#x size: %d\n",
                    pkt->req->getPaddr(), pkt->req->getSize());
            Tick lat = sendAtomic(pkt);

            handleResp(pkt, lat);
        }
    } else {
        panic("Unknown memory mode.");
    }
}

Port &
DmaDevice::getPort(const std::string &if_name, PortID idx)
{
    if (if_name == "dma") {
        return dmaPort;
    }
    return PioDevice::getPort(if_name, idx);
}

DmaReadFifo::DmaReadFifo(DmaPort &_port, size_t size,
                         unsigned max_req_size,
                         unsigned max_pending,
                         Request::Flags flags)
    : maxReqSize(max_req_size), fifoSize(size),
      reqFlags(flags), port(_port), proxy(port, port.sys->cacheLineSize()),
      cacheLineSize(port.sys->cacheLineSize()), buffer(size)
{
    freeRequests.resize(max_pending);
    for (auto &e : freeRequests)
        e.reset(new DmaDoneEvent(this, max_req_size));

}

DmaReadFifo::~DmaReadFifo()
{
    for (auto &p : pendingRequests) {
        DmaDoneEvent *e(p.release());

        if (e->done()) {
            delete e;
        } else {
            // We can't kill in-flight DMAs, so we'll just transfer
            // ownership to the event queue so that they get freed
            // when they are done.
            e->kill();
        }
    }
}

void
DmaReadFifo::serialize(CheckpointOut &cp) const
{
    assert(pendingRequests.empty());

    SERIALIZE_CONTAINER(buffer);
    SERIALIZE_SCALAR(endAddr);
    SERIALIZE_SCALAR(nextAddr);
}

void
DmaReadFifo::unserialize(CheckpointIn &cp)
{
    UNSERIALIZE_CONTAINER(buffer);
    UNSERIALIZE_SCALAR(endAddr);
    UNSERIALIZE_SCALAR(nextAddr);
}

bool
DmaReadFifo::tryGet(uint8_t *dst, size_t len)
{
    if (buffer.size() >= len) {
        buffer.read(dst, len);
        resumeFill();
        return true;
    } else {
        return false;
    }
}

void
DmaReadFifo::get(uint8_t *dst, size_t len)
{
    panic_if(!tryGet(dst, len), "Buffer underrun in DmaReadFifo::get()");
}

void
DmaReadFifo::startFill(Addr start, size_t size)
{
    assert(atEndOfBlock());

    nextAddr = start;
    endAddr = start + size;
    resumeFill();
}

void
DmaReadFifo::stopFill()
{
    // Prevent new DMA requests by setting the next address to the end
    // address. Pending requests will still complete.
    nextAddr = endAddr;

    // Flag in-flight accesses as canceled. This prevents their data
    // from being written to the FIFO.
    for (auto &p : pendingRequests)
        p->cancel();
}

void
DmaReadFifo::resumeFill()
{
    // Don't try to fetch more data if we are draining. This ensures
    // that the DMA engine settles down before we checkpoint it.
    if (drainState() == DrainState::Draining)
        return;

    const bool old_eob(atEndOfBlock());

    if (port.sys->bypassCaches())
        resumeFillFunctional();
    else
        resumeFillTiming();

    if (!old_eob && atEndOfBlock())
        onEndOfBlock();
}

void
DmaReadFifo::resumeFillFunctional()
{
    const size_t fifo_space = buffer.capacity() - buffer.size();
    if (fifo_space >= cacheLineSize || buffer.capacity() < cacheLineSize) {
        const size_t block_remaining = endAddr - nextAddr;
        const size_t xfer_size = std::min(fifo_space, block_remaining);
        std::vector<uint8_t> tmp_buffer(xfer_size);

        assert(pendingRequests.empty());
        DPRINTF(DMA, "KVM Bypassing startAddr=%#x xfer_size=%#x " \
                "fifo_space=%#x block_remaining=%#x\n",
                nextAddr, xfer_size, fifo_space, block_remaining);

        proxy.readBlob(nextAddr, tmp_buffer.data(), xfer_size);
        buffer.write(tmp_buffer.begin(), xfer_size);
        nextAddr += xfer_size;
    }
}

void
DmaReadFifo::resumeFillTiming()
{
    size_t size_pending(0);
    for (auto &e : pendingRequests)
        size_pending += e->requestSize();

    while (!freeRequests.empty() && !atEndOfBlock()) {
        const size_t req_size(std::min(maxReqSize, endAddr - nextAddr));
        if (buffer.size() + size_pending + req_size > fifoSize)
            break;

        DmaDoneEventUPtr event(std::move(freeRequests.front()));
        freeRequests.pop_front();
        assert(event);

        event->reset(req_size);
        port.dmaAction(MemCmd::ReadReq, nextAddr, req_size, event.get(),
                       event->data(), 0, reqFlags);
        nextAddr += req_size;
        size_pending += req_size;

        pendingRequests.emplace_back(std::move(event));
    }
}

void
DmaReadFifo::dmaDone()
{
    const bool old_active(isActive());

    handlePending();
    resumeFill();

    if (old_active && !isActive())
        onIdle();
}

void
DmaReadFifo::handlePending()
{
    while (!pendingRequests.empty() && pendingRequests.front()->done()) {
        // Get the first finished pending request
        DmaDoneEventUPtr event(std::move(pendingRequests.front()));
        pendingRequests.pop_front();

        if (!event->canceled())
            buffer.write(event->data(), event->requestSize());

        // Move the event to the list of free requests
        freeRequests.emplace_back(std::move(event));
    }

    if (pendingRequests.empty())
        signalDrainDone();
}

DrainState
DmaReadFifo::drain()
{
    return pendingRequests.empty() ?
        DrainState::Drained : DrainState::Draining;
}


DmaReadFifo::DmaDoneEvent::DmaDoneEvent(DmaReadFifo *_parent, size_t max_size)
    : parent(_parent), _data(max_size, 0)
{
}

void
DmaReadFifo::DmaDoneEvent::kill()
{
    parent = nullptr;
    setFlags(AutoDelete);
}

void
DmaReadFifo::DmaDoneEvent::cancel()
{
    _canceled = true;
}

void
DmaReadFifo::DmaDoneEvent::reset(size_t size)
{
    assert(size <= _data.size());
    _done = false;
    _canceled = false;
    _requestSize = size;
}

void
DmaReadFifo::DmaDoneEvent::process()
{
    if (!parent)
        return;

    assert(!_done);
    _done = true;
    parent->dmaDone();
}