dev: Add support for a simple debug UART

Add a simple memory-mapped device that forwards writes to a serial
devices and treats reads as reads from the device. Unlike real UART
models, this one doesn't support interrupts.

This is useful to implement various debug devices that exist in many
systems.

Change-Id: I1e4300e4d3b70825a15d03f47d4e026941f9066c
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jack Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/10025
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>

4 files changed, 180 insertions, 0 deletions

diff --git a/src/dev/serial/SConscript b/src/dev/serial/SConscript
index b9f13f54b..9fe5ece83 100644
--- a/src/dev/serial/SConscript
+++ b/src/dev/serial/SConscript
@@ -50,6 +50,7 @@ SimObject('Terminal.py')
 SimObject('Uart.py')
 
 Source('serial.cc')
+Source('simple.cc')
 Source('terminal.cc')
 Source('uart.cc')
 Source('uart8250.cc')
diff --git a/src/dev/serial/Uart.py b/src/dev/serial/Uart.py
index 53337059b..029d46c4f 100644
--- a/src/dev/serial/Uart.py
+++ b/src/dev/serial/Uart.py
@@ -1,3 +1,15 @@
+# Copyright (c) 2018 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.
+#
 # Copyright (c) 2005-2007 The Regents of The University of Michigan
 # All rights reserved.
 #
@@ -38,6 +50,14 @@ class Uart(BasicPioDevice):
     platform = Param.Platform(Parent.any, "Platform this device is part of.")
     device = Param.SerialDevice(Parent.any, "The terminal")
 
+class SimpleUart(Uart):
+    type = 'SimpleUart'
+    cxx_header = "dev/serial/simple.hh"
+    big_endian = Param.Bool(False, "Is the device Big Endian?")
+    pio_size = Param.Addr(0x4, "Size of address range")
+    end_on_eot = Param.Bool(False, "End the simulation when a EOT is "\
+                            "received on the UART")
+
 class Uart8250(Uart):
     type = 'Uart8250'
     cxx_header = "dev/serial/uart8250.hh"
diff --git a/src/dev/serial/simple.cc b/src/dev/serial/simple.cc
new file mode 100644
index 000000000..aea94f995
--- /dev/null
+++ b/src/dev/serial/simple.cc
@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2018 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: Andreas Sandberg
+ */
+
+#include "dev/serial/simple.hh"
+
+#include "mem/packet.hh"
+#include "mem/packet_access.hh"
+#include "params/SimpleUart.hh"
+#include "sim/sim_exit.hh"
+
+SimpleUart::SimpleUart(const SimpleUartParams *p)
+    : Uart(p, p->pio_size),
+      byteOrder(p->big_endian ? BigEndianByteOrder : LittleEndianByteOrder),
+      endOnEOT(p->end_on_eot)
+{
+}
+
+Tick
+SimpleUart::read(PacketPtr pkt)
+{
+    assert(pkt->getAddr() >= pioAddr && pkt->getAddr() < pioAddr + pioSize);
+
+    uint64_t data = 0;
+
+    if (device->dataAvailable())
+        data = device->readData();
+
+    pkt->setUintX(data, byteOrder);
+
+    pkt->makeAtomicResponse();
+    return pioDelay;
+}
+
+Tick
+SimpleUart::write(PacketPtr pkt)
+{
+
+    assert(pkt->getAddr() >= pioAddr && pkt->getAddr() < pioAddr + pioSize);
+
+    uint8_t data = (uint8_t)pkt->getUintX(byteOrder);
+    if (data == 0x04 && endOnEOT)
+        exitSimLoop("UART received EOT", 0);
+
+    device->writeData(data);
+
+    pkt->makeAtomicResponse();
+    return pioDelay;
+}
+
+SimpleUart *
+SimpleUartParams::create()
+{
+    return new SimpleUart(this);
+}
diff --git a/src/dev/serial/simple.hh b/src/dev/serial/simple.hh
new file mode 100644
index 000000000..769c04baf
--- /dev/null
+++ b/src/dev/serial/simple.hh
@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2018 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: Andreas Sandberg
+ */
+
+
+#ifndef __DEV_SERIAL_SIMPLE_HH__
+#define __DEV_SERIAL_SIMPLE_HH__
+
+#include "dev/serial/uart.hh"
+
+struct SimpleUartParams;
+
+class SimpleUart : public Uart
+{
+  public:
+    SimpleUart(const SimpleUartParams *p);
+
+  public: // PioDevice
+    Tick read(PacketPtr pkt) override;
+    Tick write(PacketPtr pkt) override;
+
+  public: // Uart
+    void dataAvailable() override {
+        // We don't support interrupts, so ignore the data available
+        // call.
+    };
+
+  protected: // Configuration
+    const ByteOrder byteOrder;
+
+    const bool endOnEOT;
+};
+
+#endif // __DEV_SERIAL_SIMPLE_HH__