arch-riscv: PLIC Implementation
This patch contains the implementation for the RISC-V PLIC.
The PLIC Memory Map is based on the SiFive U54MC datasheet.
The PLIC models a 3-cycle latency as stated in the RISC-V
specs.
Change-Id: I571c7bd3bd2918c92e4f207a1b57cf9d06e9c72f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/40598
Reviewed-by: Ayaz Akram <yazakram@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
diff --git a/src/dev/riscv/Plic.py b/src/dev/riscv/Plic.py
new file mode 100644
index 0000000..0e2f386
--- /dev/null
+++ b/src/dev/riscv/Plic.py
@@ -0,0 +1,52 @@
+# Copyright (c) 2021 Huawei International
+# 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.
+
+from m5.objects.Device import BasicPioDevice
+from m5.params import *
+from m5.proxy import *
+
+class Plic(BasicPioDevice):
+ """
+ This implementation of PLIC is based on
+ the SiFive U54MC datasheet:
+ https://sifive.cdn.prismic.io/sifive/fab000f6-
+ 0e07-48d0-9602-e437d5367806_sifive_U54MC_rtl_
+ full_20G1.03.00_manual.pdf
+ """
+ type = 'Plic'
+ cxx_header = 'dev/riscv/plic.hh'
+ intrctrl = Param.IntrControl(Parent.any, "interrupt controller")
+ pio_size = Param.Addr(0x4000000, "PIO Size")
+ n_src = Param.Int("Number of interrupt sources")
diff --git a/src/dev/riscv/SConscript b/src/dev/riscv/SConscript
index 43946c2..08d462b 100755
--- a/src/dev/riscv/SConscript
+++ b/src/dev/riscv/SConscript
@@ -31,9 +31,12 @@
if env['TARGET_ISA'] == 'riscv':
SimObject('Clint.py')
+ SimObject('Plic.py')
SimObject('RTC.py')
DebugFlag('Clint')
+ DebugFlag('Plic')
Source('clint.cc')
+ Source('plic.cc')
Source('rtc.cc')
diff --git a/src/dev/riscv/plic.cc b/src/dev/riscv/plic.cc
new file mode 100644
index 0000000..60ac192
--- /dev/null
+++ b/src/dev/riscv/plic.cc
@@ -0,0 +1,544 @@
+/*
+ * Copyright (c) 2021 Huawei International
+ * 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.
+ */
+
+
+#include "dev/riscv/plic.hh"
+
+#include <algorithm>
+
+#include "arch/riscv/registers.hh"
+#include "debug/Plic.hh"
+#include "mem/packet.hh"
+#include "mem/packet_access.hh"
+#include "params/Plic.hh"
+#include "sim/system.hh"
+
+using namespace RiscvISA;
+
+Plic::Plic(const Params ¶ms) :
+ BasicPioDevice(params, params.pio_size),
+ system(params.system),
+ intrctrl(params.intrctrl),
+ nSrc(params.n_src),
+ registers(params.name, pioAddr, this),
+ update([this]{updateOutput();}, name() + ".update")
+{
+}
+
+void
+Plic::post(int src_id)
+{
+ // Sanity check
+ assert(src_id < nSrc && src_id >= 0);
+
+ // Update pending bit
+ int src_index = src_id >> 5;
+ int src_offset = src_id & 0x1F;
+
+ uint32_t& pending = registers.pending[src_index].get();
+ std::bitset<32> pending_bits(pending);
+ pending_bits[src_offset] = 1;
+ pending = (uint32_t) pending_bits.to_ulong();
+
+ // Update states
+ pendingPriority[src_id] = registers.priority[src_id].get();
+ for (int i = 0; i < nContext; i++) {
+ bool enabled = bits(registers.enable[i][src_index].get(), src_offset);
+ effPriority[i][src_id] = enabled ? pendingPriority[src_id] : 0;
+ }
+ DPRINTF(Plic,
+ "Int post request - source: %#x, current priority: %#x\n",
+ src_id, pendingPriority[src_id]);
+
+ // Propagate output changes
+ propagateOutput();
+}
+
+void
+Plic::clear(int src_id)
+{
+ // Sanity check
+ assert(src_id < nSrc);
+ assert(src_id >= 0);
+
+ // Update pending bit
+ int src_index = src_id >> 5;
+ int src_offset = src_id & 0x1F;
+ uint32_t& pending = registers.pending[src_index].get();
+ std::bitset<32> pending_bits(pending);
+ pending_bits[src_offset] = 0;
+ pending = (uint32_t) pending_bits.to_ulong();
+
+ // Update states
+ pendingPriority[src_id] = 0;
+ for (int i = 0; i < nContext; i++) {
+ effPriority[i][src_id] = 0;
+ }
+ DPRINTF(Plic,
+ "Int clear request - source: %#x, current priority: %#x\n",
+ src_id, pendingPriority[src_id]);
+
+ // Propagate output changes
+ propagateOutput();
+}
+
+Tick
+Plic::read(PacketPtr pkt)
+{
+ // Check for atomic operation
+ bool is_atomic = pkt->isAtomicOp() && pkt->cmd == MemCmd::SwapReq;
+ DPRINTF(Plic,
+ "Read request - addr: %#x, size: %#x, atomic:%d\n",
+ pkt->getAddr(), pkt->getSize(), is_atomic);
+
+ // Perform register read
+ registers.read(pkt->getAddr(), pkt->getPtr<void>(), pkt->getSize());
+
+ if (is_atomic) {
+ // Perform atomic operation
+ (*(pkt->getAtomicOp()))(pkt->getPtr<uint8_t>());
+ return write(pkt);
+ } else {
+ pkt->makeResponse();
+ return pioDelay;
+ }
+}
+
+Tick
+Plic::write(PacketPtr pkt)
+{
+ DPRINTF(Plic,
+ "Write request - addr: %#x, size: %#x\n",
+ pkt->getAddr(), pkt->getSize());
+
+ // Perform register write
+ registers.write(pkt->getAddr(), pkt->getPtr<void>(), pkt->getSize());
+
+ // Propagate output changes
+ propagateOutput();
+
+ // Apply threshold changes
+ updateInt();
+
+ pkt->makeResponse();
+ return pioDelay;
+}
+
+void
+Plic::init()
+{
+ // Number of contexts
+ nContext = system->threads.size() * 2;
+ // Number of 32-bit pending registesrs where
+ // each bit correspondings to one interrupt source
+ nSrc32 = divCeil(nSrc, 32);
+
+ // Setup register bank
+ registers.init();
+
+ // Setup internal states
+ pendingPriority.resize(nSrc, 0x0);
+ for (int i = 0; i < nContext; i++) {
+ std::vector<uint32_t> context_priority(nSrc, 0x0);
+ effPriority.push_back(context_priority);
+ }
+ lastID.resize(nContext, 0x0);
+
+ // Setup outputs
+ output = PlicOutput{
+ std::vector<uint32_t>(nContext, 0x0),
+ std::vector<uint32_t>(nContext, 0x0)};
+
+ DPRINTF(Plic,
+ "Device init - %d contexts, %d sources, %d pending registers\n",
+ nContext, nSrc, nSrc32);
+
+ BasicPioDevice::init();
+}
+
+void
+Plic::PlicRegisters::init()
+{
+ using namespace std::placeholders;
+
+ // Calculate reserved space size
+ const size_t reserve0_size = pendingStart - plic->nSrc * 4;
+ reserved.emplace_back("reserved0", reserve0_size);
+ const size_t reserve1_size = enableStart - pendingStart
+ - plic->nSrc32 * 4;
+ reserved.emplace_back("reserved1", reserve1_size);
+ const size_t reserve2_size = thresholdStart - enableStart
+ - plic->nSrc32 * plic->nContext * enablePadding;
+ reserved.emplace_back("reserved2", reserve2_size);
+ const size_t reserve3_size = plic->pioSize - thresholdStart
+ - plic->nContext * thresholdPadding;
+ reserved.emplace_back("reserved3", reserve3_size);
+
+ // Sanity check
+ assert(plic->pioSize >= thresholdStart
+ + plic->nContext * thresholdPadding);
+ assert((int) plic->pioSize <= maxBankSize);
+
+ // Calculate hole sizes
+ const size_t enable_hole_size = enablePadding - plic->nSrc32 * 4;
+ const size_t claim_hole_size = thresholdPadding - 0x8;
+
+ // Initialize registers
+ for (int i = 0; i < plic->nSrc; i++) {
+ priority.emplace_back(
+ std::string("priority") + std::to_string(i), 0);
+ }
+ for (int i = 0; i < plic->nSrc32; i++) {
+ pending.emplace_back(
+ std::string("pending") + std::to_string(i), 0);
+ }
+ for (int i = 0; i < plic->nContext; i++) {
+
+ enable.push_back(std::vector<Register32>());
+ for (int j = 0; j < plic->nSrc32; j++) {
+ enable[i].emplace_back(
+ std::string("enable") + std::to_string(i)
+ + "_" + std::to_string(j), 0);
+ }
+ enable_holes.emplace_back(
+ std::string("enable_hole") + std::to_string(i), enable_hole_size);
+
+ threshold.emplace_back(
+ std::string("threshold") + std::to_string(i), 0);
+ claim.emplace_back(
+ std::string("claim") + std::to_string(i), 0);
+ claim_holes.emplace_back(
+ std::string("claim_hole") + std::to_string(i), claim_hole_size);
+ }
+
+ // Add registers to bank
+ // Priority
+ for (int i = 0; i < plic->nSrc; i++) {
+ auto write_cb = std::bind(&Plic::writePriority, plic, _1, _2, i);
+ priority[i].writer(write_cb);
+ addRegister(priority[i]);
+ }
+ addRegister(reserved[0]);
+
+ // Pending
+ for (int i = 0; i < plic->nSrc32; i++) {
+ pending[i].readonly();
+ addRegister(pending[i]);
+ }
+ addRegister(reserved[1]);
+
+ // Enable
+ for (int i = 0; i < plic->nContext; i++) {
+ for (int j = 0; j < plic->nSrc32; j++) {
+ auto write_cb = std::bind(&Plic::writeEnable, plic, _1, _2, j, i);
+ enable[i][j].writer(write_cb);
+ addRegister(enable[i][j]);
+ }
+ addRegister(enable_holes[i]);
+ }
+ addRegister(reserved[2]);
+
+ // Threshold and claim
+ for (int i = 0; i < plic->nContext; i++) {
+ auto threshold_cb = std::bind(&Plic::writeThreshold, plic, _1, _2, i);
+ threshold[i].writer(threshold_cb);
+ auto read_cb = std::bind(&Plic::readClaim, plic, _1, i);
+ auto write_cb = std::bind(&Plic::writeClaim, plic, _1, _2, i);
+ claim[i].reader(read_cb)
+ .writer(write_cb);
+ addRegister(threshold[i]);
+ addRegister(claim[i]);
+ addRegister(claim_holes[i]);
+ }
+ addRegister(reserved[3]);
+}
+
+void
+Plic::writePriority(Register32& reg, const uint32_t& data, const int src_id)
+{
+ reg.update(data);
+
+ // Calculate indices
+ int src_index = src_id >> 5;
+ int src_offset = src_id & 0x1F;
+
+ // Update states
+ bool pending = bits(registers.pending[src_index].get(), src_offset);
+ pendingPriority[src_id] = pending ? reg.get() : 0;
+ for (int i = 0; i < nContext; i++) {
+ bool enabled = bits(
+ registers.enable[i][src_index].get(), src_offset);
+ effPriority[i][src_id] = enabled ? pendingPriority[src_id] : 0;
+ }
+
+ DPRINTF(Plic,
+ "Priority updated - src: %d, val: %d\n",
+ src_id, reg.get());
+}
+
+void
+Plic::writeEnable(Register32& reg, const uint32_t& data,
+ const int src32_id, const int context_id)
+{
+ reg.update(data);
+
+ for (int i = 0; i < 32; i ++) {
+ int src_id = (src32_id << 5) + i;
+ if (src_id < nSrc) {
+ effPriority[context_id][src_id] =
+ bits(reg.get(), i) ? pendingPriority[src_id] : 0;
+ }
+ }
+ DPRINTF(Plic,
+ "Enable updated - context: %d, src32: %d, val: %#x\n",
+ context_id, src32_id, reg.get());
+}
+
+void
+Plic::writeThreshold(Register32& reg, const uint32_t& data,
+ const int context_id)
+{
+ DPRINTF(Plic,
+ "Threshold updated - context: %d, val: %d\n",
+ context_id, reg.get());
+}
+
+uint32_t
+Plic::readClaim(Register32& reg, const int context_id)
+{
+ if (lastID[context_id] == 0) {
+ // Calculate indices
+ uint32_t max_int_id = output.maxID[context_id];
+ int src_index = max_int_id >> 5;
+ int src_offset = max_int_id & 0x1F;
+
+ // Check pending bits
+ if (bits(registers.pending[src_index].get(), src_offset)) {
+ lastID[context_id] = max_int_id;
+ DPRINTF(Plic,
+ "Claim success - context: %d, interrupt ID: %d\n",
+ context_id, max_int_id);
+ clear(max_int_id);
+ reg.update(max_int_id);
+ } else {
+ DPRINTF(Plic,
+ "Claim already cleared - context: %d, interrupt ID: %d\n",
+ context_id, max_int_id);
+ reg.update(0);
+ }
+ } else {
+ warn("PLIC claim failed (not completed) - context: %d", context_id);
+ reg.update(0);
+ }
+ return reg.get();
+}
+
+void
+Plic::writeClaim(Register32& reg, const uint32_t& data, const int context_id)
+{
+ reg.update(data);
+
+ /**
+ * Plic spec states that this error should be silently ignored.
+ * However, this is not supposed to happen.
+ */
+ assert(lastID[context_id] == reg.get());
+ lastID[context_id] = 0;
+ DPRINTF(Plic,
+ "Complete - context: %d, interrupt ID: %d\n",
+ context_id, reg.get());
+}
+
+void
+Plic::propagateOutput()
+{
+ // Calculate new output
+ PlicOutput new_output{
+ std::vector<uint32_t>(nContext, 0x0),
+ std::vector<uint32_t>(nContext, 0x0)};
+ uint32_t max_id;
+ uint32_t max_priority;
+ for (int i = 0; i < nContext; i++) {
+ max_id = max_element(effPriority[i].begin(),
+ effPriority[i].end()) - effPriority[i].begin();
+ max_priority = effPriority[i][max_id];
+ new_output.maxID[i] = max_id;
+ new_output.maxPriority[i] = max_priority;
+ }
+
+ // Add new output to outputQueue
+ Tick next_update = curTick() + cyclesToTicks(Cycles(3));
+ if (outputQueue.find(next_update) != outputQueue.end()) {
+ outputQueue[next_update] = new_output;
+ } else {
+ outputQueue.insert({next_update, new_output});
+ }
+
+ // Schedule next update event
+ if (!update.scheduled()) {
+ DPRINTF(Plic, "Update scheduled - tick: %d\n", next_update);
+ schedule(update, next_update);
+ }
+}
+
+void
+Plic::updateOutput()
+{
+ DPRINTF(Plic, "Update triggered\n");
+ // Set current output to new output
+ output = outputQueue.begin()->second;
+ outputQueue.erase(outputQueue.begin()->first);
+
+ // Schedule next update event (if any)
+ if (!outputQueue.empty()) {
+ DPRINTF(Plic, "Update scheduled - tick: %d\n",
+ outputQueue.begin()->first);
+ schedule(update, outputQueue.begin()->first);
+ }
+
+ updateInt();
+}
+
+void
+Plic::updateInt()
+{
+ // Update xEIP lines
+ for (int i = 0; i < nContext; i++) {
+ int thread_id = i >> 1;
+ int int_id = (i & 1) ?
+ ExceptionCode::INT_EXT_SUPER : ExceptionCode::INT_EXT_MACHINE;
+
+ uint32_t max_id = output.maxID[i];
+ uint32_t priority = output.maxPriority[i];
+ uint32_t threshold = registers.threshold[i].get();
+ if (priority > threshold && max_id > 0) {
+ DPRINTF(Plic,
+ "Int posted - thread: %d, int id: %d, ",
+ thread_id, int_id);
+ DPRINTF(Plic,
+ "pri: %d, thres: %d\n", priority, threshold);
+ intrctrl->post(thread_id, int_id, 0);
+ } else {
+ if (priority > 0) {
+ DPRINTF(Plic,
+ "Int filtered - thread: %d, int id: %d, ",
+ thread_id, int_id);
+ DPRINTF(Plic,
+ "pri: %d, thres: %d\n", priority, threshold);
+ }
+ intrctrl->clear(thread_id, int_id, 0);
+ }
+ }
+}
+
+void
+Plic::serialize(CheckpointOut &cp) const
+{
+ int n_outputs = 0;
+
+ for (auto const ®: registers.pending) {
+ paramOut(cp, reg.name(), reg);
+ }
+ for (auto const ®: registers.priority) {
+ paramOut(cp, reg.name(), reg);
+ }
+ for (auto const ®: registers.enable) {
+ for (auto const ®_inner: reg) {
+ paramOut(cp, reg_inner.name(), reg_inner);
+ }
+ }
+ for (auto const ®: registers.threshold) {
+ paramOut(cp, reg.name(), reg);
+ }
+ for (auto const ®: registers.claim) {
+ paramOut(cp, reg.name(), reg);
+ }
+ for (auto const & it : outputQueue) {
+ paramOut(cp, std::string("output_tick") +
+ std::to_string(n_outputs), it.first);
+ arrayParamOut(cp, std::string("output_id") +
+ std::to_string(n_outputs), it.second.maxID);
+ arrayParamOut(cp, std::string("output_pri") +
+ std::to_string(n_outputs), it.second.maxPriority);
+ n_outputs++;
+ }
+ SERIALIZE_SCALAR(n_outputs);
+ SERIALIZE_CONTAINER(output.maxID);
+ SERIALIZE_CONTAINER(output.maxPriority);
+}
+
+void
+Plic::unserialize(CheckpointIn &cp)
+{
+ int n_outputs;
+ UNSERIALIZE_SCALAR(n_outputs);
+
+ for (auto ®: registers.pending) {
+ paramIn(cp, reg.name(), reg);
+ }
+ for (auto ®: registers.priority) {
+ paramIn(cp, reg.name(), reg);
+ }
+ for (auto ®: registers.enable) {
+ for (auto ®_inner: reg) {
+ paramIn(cp, reg_inner.name(), reg_inner);
+ }
+ }
+ for (auto ®: registers.threshold) {
+ paramIn(cp, reg.name(), reg);
+ }
+ for (auto ®: registers.claim) {
+ paramIn(cp, reg.name(), reg);
+ }
+ for (int i = 0; i < n_outputs; i++) {
+ Tick output_tick;
+ std::vector<uint32_t> output_id;
+ std::vector<uint32_t> output_pri;
+ paramIn(cp, std::string("output_tick") +
+ std::to_string(i), output_tick);
+ arrayParamIn(cp, std::string("output_id") +
+ std::to_string(i), output_id);
+ arrayParamIn(cp, std::string("output_pri") +
+ std::to_string(i), output_pri);
+ outputQueue[output_tick] = PlicOutput{output_id, output_pri};
+ }
+ if (!outputQueue.empty()) {
+ schedule(update, outputQueue.begin()->first);
+ }
+ UNSERIALIZE_CONTAINER(output.maxID);
+ UNSERIALIZE_CONTAINER(output.maxPriority);
+}
diff --git a/src/dev/riscv/plic.hh b/src/dev/riscv/plic.hh
new file mode 100644
index 0000000..a0dfbbf
--- /dev/null
+++ b/src/dev/riscv/plic.hh
@@ -0,0 +1,283 @@
+/*
+ * Copyright (c) 2021 Huawei International
+ * 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.
+ */
+
+#ifndef __DEV_RISCV_PLIC_HH__
+#define __DEV_RISCV_PLIC_HH__
+
+#include <bitset>
+#include <map>
+
+#include "arch/riscv/interrupts.hh"
+#include "cpu/intr_control.hh"
+#include "dev/io_device.hh"
+#include "dev/reg_bank.hh"
+#include "mem/packet.hh"
+#include "mem/packet_access.hh"
+#include "params/Plic.hh"
+#include "sim/system.hh"
+
+using namespace RiscvISA;
+/**
+ * NOTE:
+ * This implementation of CLINT is based on
+ * the SiFive U54MC datasheet:
+ * https://sifive.cdn.prismic.io/sifive/fab000f6-
+ * 0e07-48d0-9602-e437d5367806_sifive_U54MC_rtl_
+ * full_20G1.03.00_manual.pdf
+ */
+
+/**
+ * PLIC Latency Model
+ * MMIO changed (aside from threshold)
+ * => update internal states
+ * => calculate new output
+ * => schedule update (3 cycles delay)
+ * => update output & schedule next update
+ * => update xEIP lines
+ *
+ * threshold changed
+ * => update xEIP lines
+ *
+ * This ensures cycle-accurate values for
+ * MMIO accesses and xEIP lines
+ *
+ * NOTE:
+ * check pending bit when returning maxID
+ * to avoid claiming by multiple contexts.
+ * Note that pending bits are not propagated
+ * through the 3-cycle delay.
+ *
+ * TODO:
+ * - Enforce access control (e.g. avoid S mode
+ * writing to M mode registers)
+ */
+
+struct PlicOutput {
+ std::vector<uint32_t> maxID;
+ std::vector<uint32_t> maxPriority;
+};
+
+class Plic : public BasicPioDevice
+{
+ // Params
+ protected:
+ System *system;
+ IntrControl *intrctrl;
+
+ // Number of interrupt sources
+ int nSrc;
+ /**
+ * Number of 32-bit pending registers needed
+ * = ceil(nSrc / 32)
+ */
+ int nSrc32;
+ /**
+ * Number of interrupt contexts
+ * = nThread * 2
+ * e.g. context 0 => thread 0 M mode
+ * context 1 => thread 0 S mode
+ * This is based on SiFive U54MC datasheet
+ */
+ int nContext;
+
+ public:
+ typedef PlicParams Params;
+ Plic(const Params ¶ms);
+
+ // External API
+ public:
+ /**
+ * Interrupt interface
+ */
+ void post(int src_id);
+ void clear(int src_id);
+
+ /**
+ * SimObject functions
+ */
+ void init() override;
+ void serialize(CheckpointOut &cp) const override;
+ void unserialize(CheckpointIn &cp) override;
+
+ protected:
+ /**
+ * PioDevice funcitons
+ */
+ Tick read(PacketPtr pkt) override;
+ Tick write(PacketPtr pkt) override;
+
+ // Register bank
+ private:
+
+ /**
+ * MMIO Registers
+ *
+ * Priority (0-7):
+ * - memory map: 0x0000000 - 0x0000FFC
+ * (1024 sources, 32 bits each)
+ * - gem5: vector<uint32_t>
+ * (index: source_id, size: n_src)
+ *
+ * ... reserved[0]
+ *
+ * Pending:
+ * - memory map: 0x0001000 - 0x0001080
+ * (1024 sources, 1 bit each)
+ * - gem5: vector<bitset<32>>
+ * (index: addr_offset, size: ceil(n_src/32))
+ *
+ * ... reserved[1]
+ *
+ * Enable:
+ * - memory map: 0x0002000 - 0x01F2000
+ * (15872 contexts, 1024 sources, 1 bit each)
+ * - gem5: vector<vector<bitset<32>>>
+ * (index: [context_id addr_offset], size: [n_context, ceil(n_src/32)])
+ * ... reserved[2]
+ *
+ * Threshold:
+ * - memory map: 0x0200000 - 0x3FFFFFC
+ * (15872 contexts, 32-bit each, 0x1000 byte spacing)
+ * - gem5: vector<uint32_t>
+ * (index: context_id, size: n_context)
+ *
+ * Claim / Complete:
+ * - memory map: 0x0200004 - 0x3FFFFFC
+ * (15872 contexts, 32-bit each, 0x1000 byte spacing)
+ * - gem5: getter / setter functions
+ *
+ * ... reserved[3]
+ */
+ class PlicRegisters: public RegisterBankLE {
+ public:
+ const Addr pendingStart = 0x1000;
+ const Addr enableStart = 0x2000;
+ const Addr thresholdStart = 0x0200000;
+ const Addr enablePadding = 0x80;
+ const Addr thresholdPadding = 0x1000;
+ const Addr maxBankSize = 0x4000000;
+
+
+ std::vector<Register32> priority;
+ std::vector<Register32> pending;
+ std::vector<std::vector<Register32>> enable;
+ std::vector<Register32> threshold;
+ std::vector<Register32> claim;
+ std::vector<RegisterRaz> enable_holes;
+ std::vector<RegisterRaz> claim_holes;
+ std::vector<RegisterRaz> reserved;
+
+ PlicRegisters(const std::string &name, Addr base, Plic* plic) :
+ RegisterBankLE(name, base),
+ plic(plic) {}
+
+ Plic* plic;
+
+ void init();
+
+ } registers;
+
+ using Register32 = PlicRegisters::Register32;
+
+ /**
+ * Register read / write callbacks
+ */
+ void writePriority(Register32& reg, const uint32_t& data,
+ const int src_id);
+
+ void writeEnable(Register32& reg, const uint32_t& data,
+ const int src32_id, const int context_id);
+
+ void writeThreshold(Register32& reg, const uint32_t& data,
+ const int context_id);
+
+ uint32_t readClaim(Register32& reg, const int context_id);
+
+ void writeClaim(Register32& reg, const uint32_t& data,
+ const int context_id);
+
+ // Latency Model
+ private:
+
+ // Internal states
+ // per-source pending * priority
+ std::vector<uint32_t> pendingPriority;
+ // per-context, per-source pendingPriority * enable
+ std::vector<std::vector<uint32_t>> effPriority;
+ // per-context last-claimed id
+ std::vector<uint32_t> lastID;
+ PlicOutput output;
+
+ /**
+ * Trigger:
+ * - Plic::post
+ * - Plic::clear
+ * - Plic::write
+ *
+ * Task:
+ * - calculate new output
+ * - schedule next update event and/or
+ * add new output to outputQueue
+ */
+ void propagateOutput();
+ std::map<Tick, PlicOutput> outputQueue;
+ EventFunctionWrapper update;
+
+ /**
+ * Trigger:
+ * - Plic::update event
+ *
+ * Task:
+ * - set current output to new output
+ * - schedule next update event (if any)
+ */
+ void updateOutput();
+
+ /**
+ * Trigger:
+ * - Plic::update event
+ * - Plic::write
+ *
+ * Task:
+ * - update xEIP lines based on new
+ * output and threshold
+ */
+ void updateInt();
+};
+
+
+#endif // __DEV_RISCV_PLIC_HH__
