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diff --git a/Documentation/arc/arc.rst b/Documentation/arc/arc.rst new file mode 100644 index 000000000..6c4d978f3 --- /dev/null +++ b/Documentation/arc/arc.rst @@ -0,0 +1,85 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Linux kernel for ARC processors +******************************* + +Other sources of information +############################ + +Below are some resources where more information can be found on +ARC processors and relevant open source projects. + +- `<https://embarc.org>`_ - Community portal for open source on ARC. + Good place to start to find relevant FOSS projects, toolchain releases, + news items and more. + +- `<https://github.com/foss-for-synopsys-dwc-arc-processors>`_ - + Home for all development activities regarding open source projects for + ARC processors. Some of the projects are forks of various upstream projects, + where "work in progress" is hosted prior to submission to upstream projects. + Other projects are developed by Synopsys and made available to community + as open source for use on ARC Processors. + +- `Official Synopsys ARC Processors website + <https://www.synopsys.com/designware-ip/processor-solutions.html>`_ - + location, with access to some IP documentation (`Programmer's Reference + Manual, AKA PRM for ARC HS processors + <https://www.synopsys.com/dw/doc.php/ds/cc/programmers-reference-manual-ARC-HS.pdf>`_) + and free versions of some commercial tools (`Free nSIM + <https://www.synopsys.com/cgi-bin/dwarcnsim/req1.cgi>`_ and + `MetaWare Light Edition <https://www.synopsys.com/cgi-bin/arcmwtk_lite/reg1.cgi>`_). + Please note though, registration is required to access both the documentation and + the tools. + +Important note on ARC processors configurability +################################################ + +ARC processors are highly configurable and several configurable options +are supported in Linux. Some options are transparent to software +(i.e cache geometries, some can be detected at runtime and configured +and used accordingly, while some need to be explicitly selected or configured +in the kernel's configuration utility (AKA "make menuconfig"). + +However not all configurable options are supported when an ARC processor +is to run Linux. SoC design teams should refer to "Appendix E: +Configuration for ARC Linux" in the ARC HS Databook for configurability +guidelines. + +Following these guidelines and selecting valid configuration options +up front is critical to help prevent any unwanted issues during +SoC bringup and software development in general. + +Building the Linux kernel for ARC processors +############################################ + +The process of kernel building for ARC processors is the same as for any other +architecture and could be done in 2 ways: + +- Cross-compilation: process of compiling for ARC targets on a development + host with a different processor architecture (generally x86_64/amd64). +- Native compilation: process of compiling for ARC on a ARC platform + (hardware board or a simulator like QEMU) with complete development environment + (GNU toolchain, dtc, make etc) installed on the platform. + +In both cases, up-to-date GNU toolchain for ARC for the host is needed. +Synopsys offers prebuilt toolchain releases which can be used for this purpose, +available from: + +- Synopsys GNU toolchain releases: + `<https://github.com/foss-for-synopsys-dwc-arc-processors/toolchain/releases>`_ + +- Linux kernel compilers collection: + `<https://mirrors.edge.kernel.org/pub/tools/crosstool>`_ + +- Bootlin's toolchain collection: `<https://toolchains.bootlin.com>`_ + +Once the toolchain is installed in the system, make sure its "bin" folder +is added in your ``PATH`` environment variable. Then set ``ARCH=arc`` & +``CROSS_COMPILE=arc-linux`` (or whatever matches installed ARC toolchain prefix) +and then as usual ``make defconfig && make``. + +This will produce "vmlinux" file in the root of the kernel source tree +usable for loading on the target system via JTAG. +If you need to get an image usable with U-Boot bootloader, +type ``make uImage`` and ``uImage`` will be produced in ``arch/arc/boot`` +folder. |