243 lines
7.3 KiB
C++
243 lines
7.3 KiB
C++
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/*
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* Copyright (c) 2012 ARM Limited
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* All rights reserved
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*
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* The license below extends only to copyright in the software and shall
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* not be construed as granting a license to any other intellectual
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* property including but not limited to intellectual property relating
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* to a hardware implementation of the functionality of the software
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* licensed hereunder. You may use the software subject to the license
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* terms below provided that you ensure that this notice is replicated
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* unmodified and in its entirety in all distributions of the software,
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* modified or unmodified, in source code or in binary form.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Authors: Peter Enns
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*/
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#include "dev/i2cbus.hh"
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#include "debug/Checkpoint.hh"
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#include "mem/packet_access.hh"
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// clang complains about std::set being overloaded with Packet::set if
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// we open up the entire namespace std
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using std::vector;
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using std::map;
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/**
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* 4KB - see e.g.
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* http://infocenter.arm.com/help/topic/com.arm.doc.dui0440b/Bbajihec.html
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*/
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I2CBus::I2CBus(const I2CBusParams *p)
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: BasicPioDevice(p, 0xfff), scl(1), sda(1), state(IDLE), currBit(7),
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i2cAddr(0x00), message(0x00)
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{
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vector<I2CDevice*> devs = p->devices;
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for (auto d : p->devices) {
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devices[d->i2cAddr()] = d;
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}
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}
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/**
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* Reads will always be to SB_CONTROLS. The kernel wants to know the state
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* of sda and scl.
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*/
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Tick
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I2CBus::read(PacketPtr pkt)
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{
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assert(pkt->getAddr() == pioAddr + SB_CONTROLS);
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pkt->set<uint8_t>((sda << 1) | scl);
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pkt->makeAtomicResponse();
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return pioDelay;
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}
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/**
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* The default i2c bus driver used by the realview pbx board writes to
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* this device one bit at a time. To facilitate making new i2c devices,
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* i2cBus::write takes care of the low-level details of the i2c protocol.
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* See the I2C Specification [1] for a detailed description of the
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* protocol.
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*
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* [1] - http://www.nxp.com/documents/user_manual/UM10204.pdf
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*/
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Tick
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I2CBus::write(PacketPtr pkt)
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{
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assert(pkt->getAddr() == pioAddr + SB_CONTROLS ||
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pkt->getAddr() == pioAddr + SB_CONTROLC);
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updateSignals(pkt);
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// Check if the bus master is starting a new transmission.
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if (isStart(pkt)) {
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state = RECEIVING_ADDR;
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message = 0x00;
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currBit = 7;
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/* Most i2c devices expect something special (e.g., command,
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* register address) in the first byte they receive so they
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* must be notified somehow that this is a new transmission.
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*/
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for (auto& d : devices) {
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d.second->i2cStart();
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}
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return pioDelay;
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}
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// Check if the bus master is ending a transmission.
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if (isEnd(pkt)) {
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state = IDLE;
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return pioDelay;
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}
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// Only change state when the clock is transitioning from low to high.
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// This may not perfectly mimic physical i2c devices but the important
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// part is to only do the following once per clock cycle.
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if (isClockSet(pkt)) {
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switch (state) {
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case RECEIVING_ADDR:
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if (currBit >= 0) {
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message |= sda << currBit;
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currBit--;
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} else {
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i2cAddr = message >> 1;
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assert(devices.find(i2cAddr) != devices.end());
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if (message & 0x01) {
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state = SENDING_DATA;
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message = devices[i2cAddr]->read();
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} else {
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state = RECEIVING_DATA;
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message = 0x00;
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}
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currBit = 7;
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sda = 0; /* Ack */
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}
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break;
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case RECEIVING_DATA:
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if (currBit >= 0) {
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message |= sda << currBit;
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currBit--;
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} else {
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devices[i2cAddr]->write(message);
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message = 0x00;
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currBit = 7;
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sda = 0; /* Ack */
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}
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break;
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case SENDING_DATA:
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if (currBit >= 0) {
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sda = (message >> currBit) & 0x01;
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currBit--;
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} else {
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if (!sda) /* Check for ack from the bus master. */
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message = devices[i2cAddr]->read();
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currBit = 7;
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}
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break;
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case IDLE:
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default:
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panic("Invalid state on posedge of clock in I2CBus::write.\n");
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break;
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}
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}
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return pioDelay;
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}
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void
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I2CBus::updateSignals(PacketPtr pkt)
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{
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uint8_t msg = pkt->get<uint8_t>();
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Addr daddr = pkt->getAddr() - pioAddr;
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switch (daddr) {
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case SB_CONTROLS:
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scl = (msg & 1) ? 1 : scl;
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sda = (msg & 2) ? 1 : sda;
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break;
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case SB_CONTROLC:
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scl = (msg & 1) ? 0 : scl;
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sda = (msg & 2) ? 0 : sda;
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break;
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default:
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break;
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}
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}
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bool
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I2CBus::isClockSet(PacketPtr pkt) const
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{
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uint8_t msg = pkt->get<uint8_t>();
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Addr daddr = pkt->getAddr() - pioAddr;
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return daddr == SB_CONTROLS && (msg & 1);
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}
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bool
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I2CBus::isStart(PacketPtr pkt) const
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{
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uint8_t msg = pkt->get<uint8_t>();
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Addr daddr = pkt->getAddr() - pioAddr;
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return scl && (msg & 2) && daddr == SB_CONTROLC;
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}
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bool
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I2CBus::isEnd(PacketPtr pkt) const
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{
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uint8_t msg = pkt->get<uint8_t>();
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Addr daddr = pkt->getAddr() - pioAddr;
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return scl && (msg & 2) && daddr == SB_CONTROLS;
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}
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void
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I2CBus::serialize(std::ostream &os)
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{
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DPRINTF(Checkpoint, "Serializing I2C bus.\n");
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SERIALIZE_SCALAR(scl);
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SERIALIZE_SCALAR(sda);
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SERIALIZE_ENUM(state);
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SERIALIZE_SCALAR(currBit);
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SERIALIZE_SCALAR(i2cAddr);
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SERIALIZE_SCALAR(message);
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}
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void
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I2CBus::unserialize(Checkpoint *cp, const std::string §ion)
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{
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DPRINTF(Checkpoint, "Unserializing I2C bus.\n");
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UNSERIALIZE_SCALAR(scl);
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UNSERIALIZE_SCALAR(sda);
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UNSERIALIZE_ENUM(state);
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UNSERIALIZE_SCALAR(currBit);
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UNSERIALIZE_SCALAR(i2cAddr);
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UNSERIALIZE_SCALAR(message);
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}
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I2CBus*
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I2CBusParams::create()
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{
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return new I2CBus(this);
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}
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