src/dev/i2c/bus.cc - arm/gem5 - Git at Google

 /*
  * Copyright (c) 2012 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
  * not be construed as granting a license to any other intellectual
  * property including but not limited to intellectual property relating
  * to a hardware implementation of the functionality of the software
  * licensed hereunder.  You may use the software subject to the license
  * terms below provided that you ensure that this notice is replicated
  * unmodified and in its entirety in all distributions of the software,
  * modified or unmodified, in source code or in binary form.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met: redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer;
  * redistributions in binary form must reproduce the above copyright
  * notice, this list of conditions and the following disclaimer in the
  * documentation and/or other materials provided with the distribution;
  * neither the name of the copyright holders nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * Authors: Peter Enns
  */

 #include "dev/i2c/bus.hh"

 #include "debug/Checkpoint.hh"
 #include "dev/i2c/device.hh"
 #include "mem/packet_access.hh"

 // clang complains about std::set being overloaded with Packet::set if
 // we open up the entire namespace std
 using std::vector;
 using std::map;

 /**
  * 4KB - see e.g.
  * http://infocenter.arm.com/help/topic/com.arm.doc.dui0440b/Bbajihec.html
  */
 I2CBus::I2CBus(const I2CBusParams *p)
     : BasicPioDevice(p, 0xfff), scl(1), sda(1), state(IDLE), currBit(7),
       i2cAddr(0x00), message(0x00)
 {
     vector<I2CDevice*> devs = p->devices;

     for (auto d : p->devices) {
         devices[d->i2cAddr()] = d;
     }
 }

 /**
  * Reads will always be to SB_CONTROLS. The kernel wants to know the state
  * of sda and scl.
  */
 Tick
 I2CBus::read(PacketPtr pkt)
 {
     assert(pkt->getAddr() == pioAddr + SB_CONTROLS);

     pkt->set<uint8_t>((sda << 1) | scl);
     pkt->makeAtomicResponse();
     return pioDelay;
 }

 /**
  * The default i2c bus driver used by the realview pbx board writes to
  * this device one bit at a time. To facilitate making new i2c devices,
  * i2cBus::write takes care of the low-level details of the i2c protocol.
  * See the I2C Specification [1] for a detailed description of the
  * protocol.
  *
  * [1] - http://www.nxp.com/documents/user_manual/UM10204.pdf
  */
 Tick
 I2CBus::write(PacketPtr pkt)
 {
     assert(pkt->getAddr() == pioAddr + SB_CONTROLS ||
            pkt->getAddr() == pioAddr + SB_CONTROLC);

     updateSignals(pkt);

     // Check if the bus master is starting a new transmission.
     if (isStart(pkt)) {
         state = RECEIVING_ADDR;
         message = 0x00;
         currBit = 7;
         /* Most i2c devices expect something special (e.g., command,
          * register address) in the first byte they receive so they
          * must be notified somehow that this is a new transmission.
          */
         for (auto& d : devices) {
             d.second->i2cStart();
         }
         return pioDelay;
     }

     // Check if the bus master is ending a transmission.
     if (isEnd(pkt)) {
         state = IDLE;
         return pioDelay;
     }

     // Only change state when the clock is transitioning from low to high.
     // This may not perfectly mimic physical i2c devices but the important
     // part is to only do the following once per clock cycle.
     if (isClockSet(pkt)) {
         switch (state) {
           case RECEIVING_ADDR:
             if (currBit >= 0) {
                 message |= sda << currBit;
                 currBit--;
             } else {
                 i2cAddr = message >> 1;
                 assert(devices.find(i2cAddr) != devices.end());
                 if (message & 0x01) {
                     state = SENDING_DATA;
                     message = devices[i2cAddr]->read();
                 } else {
                     state = RECEIVING_DATA;
                     message = 0x00;
                 }
                 currBit = 7;
                 sda = 0; /* Ack */
             }
             break;
           case RECEIVING_DATA:
             if (currBit >= 0) {
                 message |= sda << currBit;
                 currBit--;
             } else {
                 devices[i2cAddr]->write(message);
                 message = 0x00;
                 currBit = 7;
                 sda = 0; /* Ack */
             }
             break;
           case SENDING_DATA:
             if (currBit >= 0) {
                 sda = (message >> currBit) & 0x01;
                 currBit--;
             } else {
                 if (!sda) /* Check for ack from the bus master. */
                     message = devices[i2cAddr]->read();
                 currBit = 7;
             }
             break;
           case IDLE:
           default:
             panic("Invalid state on posedge of clock in I2CBus::write.\n");
             break;
         }
     }

     return pioDelay;
 }

 void
 I2CBus::updateSignals(PacketPtr pkt)
 {
     uint8_t msg = pkt->get<uint8_t>();
     Addr daddr = pkt->getAddr() - pioAddr;

     switch (daddr) {
       case SB_CONTROLS:
         scl = (msg & 1) ? 1 : scl;
         sda = (msg & 2) ? 1 : sda;
         break;
       case SB_CONTROLC:
         scl = (msg & 1) ? 0 : scl;
         sda = (msg & 2) ? 0 : sda;
         break;
       default:
         break;
     }
 }

 bool
 I2CBus::isClockSet(PacketPtr pkt) const
 {
     uint8_t msg = pkt->get<uint8_t>();
     Addr daddr = pkt->getAddr() - pioAddr;
     return daddr == SB_CONTROLS && (msg & 1);
 }

 bool
 I2CBus::isStart(PacketPtr pkt) const
 {
     uint8_t msg = pkt->get<uint8_t>();
     Addr daddr = pkt->getAddr() - pioAddr;
     return scl && (msg & 2) && daddr == SB_CONTROLC;
 }

 bool
 I2CBus::isEnd(PacketPtr pkt) const
 {
     uint8_t msg = pkt->get<uint8_t>();
     Addr daddr = pkt->getAddr() - pioAddr;
     return scl && (msg & 2) && daddr == SB_CONTROLS;
 }
 void
 I2CBus::serialize(CheckpointOut &cp) const
 {
     DPRINTF(Checkpoint, "Serializing I2C bus.\n");
     SERIALIZE_SCALAR(scl);
     SERIALIZE_SCALAR(sda);
     SERIALIZE_ENUM(state);
     SERIALIZE_SCALAR(currBit);
     SERIALIZE_SCALAR(i2cAddr);
     SERIALIZE_SCALAR(message);
 }

 void
 I2CBus::unserialize(CheckpointIn &cp)
 {
     DPRINTF(Checkpoint, "Unserializing I2C bus.\n");
     UNSERIALIZE_SCALAR(scl);
     UNSERIALIZE_SCALAR(sda);
     UNSERIALIZE_ENUM(state);
     UNSERIALIZE_SCALAR(currBit);
     UNSERIALIZE_SCALAR(i2cAddr);
     UNSERIALIZE_SCALAR(message);
 }

 I2CBus*
 I2CBusParams::create()
 {
     return new I2CBus(this);
 }
	/*
	* Copyright (c) 2012 ARM Limited
	* All rights reserved
	*
	* The license below extends only to copyright in the software and shall
	* not be construed as granting a license to any other intellectual
	* property including but not limited to intellectual property relating
	* to a hardware implementation of the functionality of the software
	* licensed hereunder. You may use the software subject to the license
	* terms below provided that you ensure that this notice is replicated
	* unmodified and in its entirety in all distributions of the software,
	* modified or unmodified, in source code or in binary form.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are
	* met: redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer;
	* redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution;
	* neither the name of the copyright holders nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*
	* Authors: Peter Enns
	*/

	#include "dev/i2c/bus.hh"

	#include "debug/Checkpoint.hh"
	#include "dev/i2c/device.hh"
	#include "mem/packet_access.hh"

	// clang complains about std::set being overloaded with Packet::set if
	// we open up the entire namespace std
	using std::vector;
	using std::map;

	/**
	* 4KB - see e.g.
	* http://infocenter.arm.com/help/topic/com.arm.doc.dui0440b/Bbajihec.html
	*/
	I2CBus::I2CBus(const I2CBusParams *p)
	: BasicPioDevice(p, 0xfff), scl(1), sda(1), state(IDLE), currBit(7),
	i2cAddr(0x00), message(0x00)
	{
	vector<I2CDevice*> devs = p->devices;

	for (auto d : p->devices) {
	devices[d->i2cAddr()] = d;
	}
	}

	/**
	* Reads will always be to SB_CONTROLS. The kernel wants to know the state
	* of sda and scl.
	*/
	Tick
	I2CBus::read(PacketPtr pkt)
	{
	assert(pkt->getAddr() == pioAddr + SB_CONTROLS);

	pkt->set<uint8_t>((sda << 1) \| scl);
	pkt->makeAtomicResponse();
	return pioDelay;
	}

	/**
	* The default i2c bus driver used by the realview pbx board writes to
	* this device one bit at a time. To facilitate making new i2c devices,
	* i2cBus::write takes care of the low-level details of the i2c protocol.
	* See the I2C Specification [1] for a detailed description of the
	* protocol.
	*
	* [1] - http://www.nxp.com/documents/user_manual/UM10204.pdf
	*/
	Tick
	I2CBus::write(PacketPtr pkt)
	{
	assert(pkt->getAddr() == pioAddr + SB_CONTROLS \|\|
	pkt->getAddr() == pioAddr + SB_CONTROLC);

	updateSignals(pkt);

	// Check if the bus master is starting a new transmission.
	if (isStart(pkt)) {
	state = RECEIVING_ADDR;
	message = 0x00;
	currBit = 7;
	/* Most i2c devices expect something special (e.g., command,
	* register address) in the first byte they receive so they
	* must be notified somehow that this is a new transmission.
	*/
	for (auto& d : devices) {
	d.second->i2cStart();
	}
	return pioDelay;
	}

	// Check if the bus master is ending a transmission.
	if (isEnd(pkt)) {
	state = IDLE;
	return pioDelay;
	}

	// Only change state when the clock is transitioning from low to high.
	// This may not perfectly mimic physical i2c devices but the important
	// part is to only do the following once per clock cycle.
	if (isClockSet(pkt)) {
	switch (state) {
	case RECEIVING_ADDR:
	if (currBit >= 0) {
	message \|= sda << currBit;
	currBit--;
	} else {
	i2cAddr = message >> 1;
	assert(devices.find(i2cAddr) != devices.end());
	if (message & 0x01) {
	state = SENDING_DATA;
	message = devices[i2cAddr]->read();
	} else {
	state = RECEIVING_DATA;
	message = 0x00;
	}
	currBit = 7;
	sda = 0; /* Ack */
	}
	break;
	case RECEIVING_DATA:
	if (currBit >= 0) {
	message \|= sda << currBit;
	currBit--;
	} else {
	devices[i2cAddr]->write(message);
	message = 0x00;
	currBit = 7;
	sda = 0; /* Ack */
	}
	break;
	case SENDING_DATA:
	if (currBit >= 0) {
	sda = (message >> currBit) & 0x01;
	currBit--;
	} else {
	if (!sda) /* Check for ack from the bus master. */
	message = devices[i2cAddr]->read();
	currBit = 7;
	}
	break;
	case IDLE:
	default:
	panic("Invalid state on posedge of clock in I2CBus::write.\n");
	break;
	}
	}

	return pioDelay;
	}

	void
	I2CBus::updateSignals(PacketPtr pkt)
	{
	uint8_t msg = pkt->get<uint8_t>();
	Addr daddr = pkt->getAddr() - pioAddr;

	switch (daddr) {
	case SB_CONTROLS:
	scl = (msg & 1) ? 1 : scl;
	sda = (msg & 2) ? 1 : sda;
	break;
	case SB_CONTROLC:
	scl = (msg & 1) ? 0 : scl;
	sda = (msg & 2) ? 0 : sda;
	break;
	default:
	break;
	}
	}

	bool
	I2CBus::isClockSet(PacketPtr pkt) const
	{
	uint8_t msg = pkt->get<uint8_t>();
	Addr daddr = pkt->getAddr() - pioAddr;
	return daddr == SB_CONTROLS && (msg & 1);
	}

	bool
	I2CBus::isStart(PacketPtr pkt) const
	{
	uint8_t msg = pkt->get<uint8_t>();
	Addr daddr = pkt->getAddr() - pioAddr;
	return scl && (msg & 2) && daddr == SB_CONTROLC;
	}

	bool
	I2CBus::isEnd(PacketPtr pkt) const
	{
	uint8_t msg = pkt->get<uint8_t>();
	Addr daddr = pkt->getAddr() - pioAddr;
	return scl && (msg & 2) && daddr == SB_CONTROLS;
	}
	void
	I2CBus::serialize(CheckpointOut &cp) const
	{
	DPRINTF(Checkpoint, "Serializing I2C bus.\n");
	SERIALIZE_SCALAR(scl);
	SERIALIZE_SCALAR(sda);
	SERIALIZE_ENUM(state);
	SERIALIZE_SCALAR(currBit);
	SERIALIZE_SCALAR(i2cAddr);
	SERIALIZE_SCALAR(message);
	}

	void
	I2CBus::unserialize(CheckpointIn &cp)
	{
	DPRINTF(Checkpoint, "Unserializing I2C bus.\n");
	UNSERIALIZE_SCALAR(scl);
	UNSERIALIZE_SCALAR(sda);
	UNSERIALIZE_ENUM(state);
	UNSERIALIZE_SCALAR(currBit);
	UNSERIALIZE_SCALAR(i2cAddr);
	UNSERIALIZE_SCALAR(message);
	}

	I2CBus*
	I2CBusParams::create()
	{
	return new I2CBus(this);
	}