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.. SPDX-License-Identifier: GPL-2.0+
.. sectionauthor:: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
QEMU MIPS
=========
Qemu for MIPS is based on the MIPS Malta board. The built Malta U-Boot
images can be used for Qemu and on physical hardware. The Malta board
supports all combinations of Little and Big Endian as well as 32 bit
and 64 bit.
Limitations & comments
----------------------
The memory size for Qemu is hard-coded to 256 MiB. For Malta Little Endian
targets an extra endianness swapped image named *u-boot-swap.bin* is
generated and required for Qemu.
Example usage
-------------
Build for 32 bit, big endian:
.. code-block:: bash
make malta_defconfig
make
UBOOT_BIN=u-boot.bin
QEMU_BIN=qemu-system-mips
QEMU_CPU=24Kc
Build for 32 bit, little endian:
.. code-block:: bash
make maltael_defconfig
make
UBOOT_BIN=u-boot-swap.bin
QEMU_BIN=qemu-system-mipsel
QEMU_CPU=24Kc
Build for 64 bit, big endian:
.. code-block:: bash
make malta64_defconfig
make
UBOOT_BIN=u-boot.bin
QEMU_BIN=qemu-system-mips64
QEMU_CPU=MIPS64R2-generic
Build for 64 bit, little endian:
.. code-block:: bash
make malta64el_defconfig
make
UBOOT_BIN=u-boot-swap.bin
QEMU_BIN=qemu-system-mips64el
QEMU_CPU=MIPS64R2-generic
Generate NOR flash image with U-Boot binary:
.. code-block:: bash
dd if=/dev/zero bs=1M count=4 | tr '\000' '\377' > pflash.img
dd if=${UBOOT_BIN} of=pflash.img conv=notrunc
Start Qemu:
.. code-block:: bash
mkdir tftproot
${QEMU_BIN} -nographic -cpu ${QEMU_CPU} -m 256 -drive if=pflash,file="$(pwd)/pflash.img",format=raw -netdev user,id=net0,tftp="$(pwd)/tftproot" -device pcnet,netdev=net0
.. code-block:: bash
U-Boot 2021.04-00963-g60279a2b1d (Apr 21 2021 - 19:54:32 +0200)
Board: MIPS Malta CoreLV
DRAM: 256 MiB
Flash: 4 MiB
Loading Environment from Flash... *** Warning - bad CRC, using default environment
In: serial@3f8
Out: serial@3f8
Err: serial@3f8
Net: pcnet#0
IDE: Bus 0: not available
maltael #
How to debug U-Boot
-------------------
In order to debug U-Boot you need to start qemu with gdb server support (-s)
and waiting the connection to start the CPU (-S). Start Qemu in the first console:
.. code-block:: bash
mkdir tftproot
${QEMU_BIN} -s -S -nographic -cpu ${QEMU_CPU} -m 256 -drive if=pflash,file="$(pwd)/pflash.img",format=raw -netdev user,id=net0,tftp="$(pwd)/tftproot" -device pcnet,netdev=net0
In the second console start gdb:
.. code-block:: bash
gdb-multiarch --eval-command "target remote :1234" u-boot
.. code-block:: bash
GNU gdb (Ubuntu 9.2-0ubuntu1~20.04) 9.2
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from u-boot...
Remote debugging using :1234
0xbfc00000 in ?? ()
(gdb) c
Continuing.
|
