/* * 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, 0x1000), scl(1), sda(1), state(IDLE), currBit(7), i2cAddr(0x00), message(0x00) { vector 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((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(); 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(); Addr daddr = pkt->getAddr() - pioAddr; return daddr == SB_CONTROLS && (msg & 1); } bool I2CBus::isStart(PacketPtr pkt) const { uint8_t msg = pkt->get(); Addr daddr = pkt->getAddr() - pioAddr; return scl && (msg & 2) && daddr == SB_CONTROLC; } bool I2CBus::isEnd(PacketPtr pkt) const { uint8_t msg = pkt->get(); 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); }