==============
OpenRISC Linux
==============

This is a port of Linux to the OpenRISC class of microprocessors; the initial
target architecture, specifically, is the 32-bit OpenRISC 1000 family (or1k).

For information about OpenRISC processors and ongoing development:

	=======		==============================
	website		https://openrisc.io
	email		linux-openrisc@vger.kernel.org
	=======		==============================

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Build instructions for OpenRISC toolchain and Linux
===================================================

In order to build and run Linux for OpenRISC, you'll need at least a basic
toolchain and, perhaps, the architectural simulator.  Steps to get these bits
in place are outlined here.

1) Toolchain

Toolchain binaries can be obtained from openrisc.io or our github releases page.
Instructions for building the different toolchains can be found on openrisc.io
or Stafford's toolchain build and release scripts.

	==========	==========================================================
	binaries	https://github.com/stffrdhrn/or1k-toolchain-build/releases
	toolchains	https://openrisc.io/software
	building	https://github.com/stffrdhrn/or1k-toolchain-build
	==========	==========================================================

2) Building

Build the Linux kernel as usual::

	make ARCH=openrisc CROSS_COMPILE="or1k-linux-" defconfig
	make ARCH=openrisc CROSS_COMPILE="or1k-linux-"

If you want to embed initramfs in the kernel, also pass ``CONFIG_INITRAMFS_SOURCE``. For example::

	make ARCH=openrisc CROSS_COMPILE="or1k-linux-" CONFIG_INITRAMFS_SOURCE="path/to/rootfs path/to/devnodes"

For more information on this, please check Documentation/filesystems/ramfs-rootfs-initramfs.rst.

3) Running on FPGA (optional)

The OpenRISC community typically uses FuseSoC to manage building and programming
an SoC into an FPGA.  The below is an example of programming a De0 Nano
development board with the OpenRISC SoC.  During the build FPGA RTL is code
downloaded from the FuseSoC IP cores repository and built using the FPGA vendor
tools.  Binaries are loaded onto the board with openocd.

::

	git clone https://github.com/olofk/fusesoc
	cd fusesoc
	sudo pip install -e .

	fusesoc init
	fusesoc build de0_nano
	fusesoc pgm de0_nano

	openocd -f interface/altera-usb-blaster.cfg \
		-f board/or1k_generic.cfg

	telnet localhost 4444
	> init
	> halt; load_image vmlinux ; reset

4) Running on a Simulator (optional)

QEMU is a processor emulator which we recommend for simulating the OpenRISC
platform.  Please follow the OpenRISC instructions on the QEMU website to get
Linux running on QEMU.  You can build QEMU yourself, but your Linux distribution
likely provides binary packages to support OpenRISC.

	=============	======================================================
	qemu openrisc	https://wiki.qemu.org/Documentation/Platforms/OpenRISC
	=============	======================================================

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Terminology
===========

In the code, the following particles are used on symbols to limit the scope
to more or less specific processor implementations:

========= =======================================
openrisc: the OpenRISC class of processors
or1k:     the OpenRISC 1000 family of processors
or1200:   the OpenRISC 1200 processor
========= =======================================

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History
========

18-11-2003	Matjaz Breskvar (phoenix@bsemi.com)
	initial port of linux to OpenRISC/or32 architecture.
        all the core stuff is implemented and seams usable.

08-12-2003	Matjaz Breskvar (phoenix@bsemi.com)
	complete change of TLB miss handling.
	rewrite of exceptions handling.
	fully functional sash-3.6 in default initrd.
	a much improved version with changes all around.

10-04-2004	Matjaz Breskvar (phoenix@bsemi.com)
	a lot of bugfixes all over.
	ethernet support, functional http and telnet servers.
	running many standard linux apps.

26-06-2004	Matjaz Breskvar (phoenix@bsemi.com)
	port to 2.6.x

30-11-2004	Matjaz Breskvar (phoenix@bsemi.com)
	lots of bugfixes and enhancements.
	added opencores framebuffer driver.

09-10-2010    Jonas Bonn (jonas@southpole.se)
	major rewrite to bring up to par with upstream Linux 2.6.36
