docs/system: openrisc: Add OpenRISC documentation

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Stafford Horne <shorne@gmail.com>

4 files changed, 125 insertions, 0 deletions

diff --git a/docs/system/openrisc/cpu-features.rst b/docs/system/openrisc/cpu-features.rst
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+CPU Features
+============
+
+The QEMU emulation of the OpenRISC architecture provides following built in
+features.
+
+- Shadow GPRs
+- MMU TLB with 128 entries, 1 way
+- Power Management (PM)
+- Programmable Interrupt Controller (PIC)
+- Tick Timer
+
+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``).
diff --git a/docs/system/openrisc/emulation.rst b/docs/system/openrisc/emulation.rst
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+OpenRISC 1000 CPU architecture support
+======================================
+
+QEMU's TCG emulation includes support for the OpenRISC or1200 implementation of
+the OpenRISC 1000 cpu architecture.
+
+The or1200 cpu also has support for the following instruction subsets:
+
+- ORBIS32 (OpenRISC Basic Instruction Set)
+- ORFPX32 (OpenRISC Floating-Point eXtension)
+
+In addition to the instruction subsets the QEMU TCG emulation also has support
+for most Class II (optional) instructions.
+
+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.
diff --git a/docs/system/openrisc/or1k-sim.rst b/docs/system/openrisc/or1k-sim.rst
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+Or1ksim board
+=============
+
+The QEMU Or1ksim machine emulates the standard OpenRISC board simulator which is
+also the standard SoC configuration.
+
+Supported devices
+-----------------
+
+ * 16550A UART
+ * ETHOC Ethernet controller
+ * SMP (OpenRISC multicore using ompic)
+
+Boot options
+------------
+
+The Or1ksim machine can be started using the ``-kernel`` and ``-initrd`` options
+to load a Linux kernel and optional disk image.
+
+.. code-block:: bash
+
+  $ qemu-system-or1k -cpu or1220 -M or1k-sim -nographic \
+        -kernel vmlinux \
+        -initrd initramfs.cpio.gz \
+        -m 128
+
+Linux guest kernel configuration
+""""""""""""""""""""""""""""""""
+
+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.
+
+Hardware configuration information
+""""""""""""""""""""""""""""""""""
+
+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.
+
+The location of the DTB will be passed in register ``r3`` to the guest operating
+system.
diff --git a/docs/system/openrisc/virt.rst b/docs/system/openrisc/virt.rst
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+'virt' generic virtual platform
+===============================
+
+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.
+
+Supported devices
+-----------------
+
+ * PCI/PCIe devices
+ * 8 virtio-mmio transport devices
+ * 16550A UART
+ * Goldfish RTC
+ * SiFive Test device for poweroff and reboot
+ * SMP (OpenRISC multicore using ompic)
+
+Boot options
+------------
+
+The virt machine can be started using the ``-kernel`` and ``-initrd`` options
+to load a Linux kernel and optional disk image. For example:
+
+.. 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
+""""""""""""""""""""""""""""""""
+
+The 'virt_defconfig' for Linux openrisc kernels includes the right drivers for
+the ``virt`` machine.
+
+Hardware configuration information
+""""""""""""""""""""""""""""""""""
+
+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.
+
+The location of the DTB will be passed in register ``r3`` to the guest operating
+system.