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docs/system: openrisc: Add OpenRISC documentation
Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Signed-off-by: Stafford Horne <shorne@gmail.com>
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CPU Features | ||
============ | ||
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The QEMU emulation of the OpenRISC architecture provides following built in | ||
features. | ||
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- Shadow GPRs | ||
- MMU TLB with 128 entries, 1 way | ||
- Power Management (PM) | ||
- Programmable Interrupt Controller (PIC) | ||
- Tick Timer | ||
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These features are on by default and the presence can be confirmed by checking | ||
the contents of the Unit Presence Register (``UPR``) and CPU Configuration | ||
Register (``CPUCFGR``). |
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OpenRISC 1000 CPU architecture support | ||
====================================== | ||
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QEMU's TCG emulation includes support for the OpenRISC or1200 implementation of | ||
the OpenRISC 1000 cpu architecture. | ||
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The or1200 cpu also has support for the following instruction subsets: | ||
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- ORBIS32 (OpenRISC Basic Instruction Set) | ||
- ORFPX32 (OpenRISC Floating-Point eXtension) | ||
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In addition to the instruction subsets the QEMU TCG emulation also has support | ||
for most Class II (optional) instructions. | ||
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For information on all OpenRISC instructions please refer to the latest | ||
architecture manual available on the OpenRISC website in the | ||
`OpenRISC Architecture <https://openrisc.io/architecture>`_ section. |
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Or1ksim board | ||
============= | ||
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The QEMU Or1ksim machine emulates the standard OpenRISC board simulator which is | ||
also the standard SoC configuration. | ||
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Supported devices | ||
----------------- | ||
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* 16550A UART | ||
* ETHOC Ethernet controller | ||
* SMP (OpenRISC multicore using ompic) | ||
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Boot options | ||
------------ | ||
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The Or1ksim machine can be started using the ``-kernel`` and ``-initrd`` options | ||
to load a Linux kernel and optional disk image. | ||
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.. code-block:: bash | ||
$ qemu-system-or1k -cpu or1220 -M or1k-sim -nographic \ | ||
-kernel vmlinux \ | ||
-initrd initramfs.cpio.gz \ | ||
-m 128 | ||
Linux guest kernel configuration | ||
"""""""""""""""""""""""""""""""" | ||
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The 'or1ksim_defconfig' for Linux openrisc kernels includes the right | ||
drivers for the or1ksim machine. If you would like to run an SMP system | ||
choose the 'simple_smp_defconfig' config. | ||
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Hardware configuration information | ||
"""""""""""""""""""""""""""""""""" | ||
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The ``or1k-sim`` board automatically generates a device tree blob ("dtb") | ||
which it passes to the guest. This provides information about the | ||
addresses, interrupt lines and other configuration of the various devices | ||
in the system. | ||
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The location of the DTB will be passed in register ``r3`` to the guest operating | ||
system. |
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'virt' generic virtual platform | ||
=============================== | ||
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The ``virt`` board is a platform which does not correspond to any | ||
real hardware; it is designed for use in virtual machines. | ||
It is the recommended board type if you simply want to run | ||
a guest such as Linux and do not care about reproducing the | ||
idiosyncrasies and limitations of a particular bit of real-world | ||
hardware. | ||
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Supported devices | ||
----------------- | ||
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* PCI/PCIe devices | ||
* 8 virtio-mmio transport devices | ||
* 16550A UART | ||
* Goldfish RTC | ||
* SiFive Test device for poweroff and reboot | ||
* SMP (OpenRISC multicore using ompic) | ||
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Boot options | ||
------------ | ||
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The virt machine can be started using the ``-kernel`` and ``-initrd`` options | ||
to load a Linux kernel and optional disk image. For example: | ||
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.. code-block:: bash | ||
$ qemu-system-or1k -cpu or1220 -M or1k-sim -nographic \ | ||
-device virtio-net-device,netdev=user -netdev user,id=user,net=10.9.0.1/24,host=10.9.0.100 \ | ||
-device virtio-blk-device,drive=d0 -drive file=virt.qcow2,id=d0,if=none,format=qcow2 \ | ||
-kernel vmlinux \ | ||
-initrd initramfs.cpio.gz \ | ||
-m 128 | ||
Linux guest kernel configuration | ||
"""""""""""""""""""""""""""""""" | ||
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The 'virt_defconfig' for Linux openrisc kernels includes the right drivers for | ||
the ``virt`` machine. | ||
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Hardware configuration information | ||
"""""""""""""""""""""""""""""""""" | ||
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The ``virt`` board automatically generates a device tree blob ("dtb") which it | ||
passes to the guest. This provides information about the addresses, interrupt | ||
lines and other configuration of the various devices in the system. | ||
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The location of the DTB will be passed in register ``r3`` to the guest operating | ||
system. |
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.. _OpenRISC-System-emulator: | ||
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OpenRISC System emulator | ||
~~~~~~~~~~~~~~~~~~~~~~~~ | ||
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QEMU can emulate 32-bit OpenRISC CPUs using the ``qemu-system-or1k`` executable. | ||
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OpenRISC CPUs are generally built into "system-on-chip" (SoC) designs that run | ||
on FPGAs. These SoCs are based on the same core architecture as the or1ksim | ||
(the original OpenRISC instruction level simulator) which QEMU supports. For | ||
this reason QEMU does not need to support many different boards to support the | ||
OpenRISC hardware ecosystem. | ||
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The OpenRISC CPU supported by QEMU is the ``or1200``, it supports an MMU and can | ||
run linux. | ||
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Choosing a board model | ||
====================== | ||
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For QEMU's OpenRISC system emulation, you must specify which board model you | ||
want to use with the ``-M`` or ``--machine`` option; the default machine is | ||
``or1k-sim``. | ||
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If you intend to boot Linux, it is possible to have a single kernel image that | ||
will boot on any of the QEMU machines. To do this one would compile all required | ||
drivers into the kernel. This is possible because QEMU will create a device tree | ||
structure that describes the QEMU machine and pass a pointer to the structure to | ||
the kernel. The kernel can then use this to configure itself for the machine. | ||
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However, typically users will have specific firmware images for a specific machine. | ||
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If you already have a system image or a kernel that works on hardware and you | ||
want to boot with QEMU, check whether QEMU lists that machine in its ``-machine | ||
help`` output. If it is listed, then you can probably use that board model. If | ||
it is not listed, then unfortunately your image will almost certainly not boot | ||
on QEMU. (You might be able to extract the filesystem and use that with a | ||
different kernel which boots on a system that QEMU does emulate.) | ||
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If you don't care about reproducing the idiosyncrasies of a particular | ||
bit of hardware, such as small amount of RAM, no PCI or other hard disk, etc., | ||
and just want to run Linux, the best option is to use the ``virt`` board. This | ||
is a platform which doesn't correspond to any real hardware and is designed for | ||
use in virtual machines. You'll need to compile Linux with a suitable | ||
configuration for running on the ``virt`` board. ``virt`` supports PCI, virtio | ||
and large amounts of RAM. | ||
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Board-specific documentation | ||
============================ | ||
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.. | ||
This table of contents should be kept sorted alphabetically | ||
by the title text of each file, which isn't the same ordering | ||
as an alphabetical sort by filename. | ||
.. toctree:: | ||
:maxdepth: 1 | ||
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openrisc/or1k-sim | ||
openrisc/virt | ||
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Emulated CPU architecture support | ||
================================= | ||
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.. toctree:: | ||
openrisc/emulation | ||
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OpenRISC CPU features | ||
===================== | ||
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.. toctree:: | ||
openrisc/cpu-features |
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target-m68k | ||
target-mips | ||
target-ppc | ||
target-openrisc | ||
target-riscv | ||
target-rx | ||
target-s390x | ||
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