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/*
* 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/i2cbus.hh"
#include "debug/Checkpoint.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);
}
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