Merge tag 'docs-5.17' of git://git.lwn.net/linux

SPHINXBUILD   = sphinx-build

SPHINXOPTS    =

SPHINXDIRS    = .

DOCS_THEME    =

DOCS_CSS      =

_SPHINXDIRS   = $(sort $(patsubst $(srctree)/Documentation/%/index.rst,%,$(wildcard $(srctree)/Documentation/*/index.rst)))

SPHINX_CONF   = conf.py

PAPER         =

	-D version=$(KERNELVERSION) -D release=$(KERNELRELEASE) \

	$(ALLSPHINXOPTS) \

	$(abspath $(srctree)/$(src)/$5) \

	$(abspath $(BUILDDIR)/$3/$4)

	$(abspath $(BUILDDIR)/$3/$4) && \

	if [ "x$(DOCS_CSS)" != "x" ]; then \

		cp $(if $(patsubst /%,,$(DOCS_CSS)),$(abspath $(srctree)/$(DOCS_CSS)),$(DOCS_CSS)) $(BUILDDIR)/$3/_static/; \

	fi

htmldocs:

	@$(srctree)/scripts/sphinx-pre-install --version-check

	@echo  '  make SPHINX_CONF={conf-file} [target] use *additional* sphinx-build'

	@echo  '  configuration. This is e.g. useful to build with nit-picking config.'

	@echo

	@echo  '  make DOCS_THEME={sphinx-theme} selects a different Sphinx theme.'

	@echo

	@echo  '  make DOCS_CSS={a .css file} adds a DOCS_CSS override file for html/epub output.'

	@echo

	@echo  '  Default location for the generated documents is Documentation/output'

   before invoking any firmware code to prevent Spectre variant 2 exploits

   using the firmware.

   Using kernel address space randomization (CONFIG_RANDOMIZE_SLAB=y

   Using kernel address space randomization (CONFIG_RANDOMIZE_BASE=y

   and CONFIG_SLAB_FREELIST_RANDOM=y in the kernel configuration) makes

   attacks on the kernel generally more difficult.

.. 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.

.. SPDX-License-Identifier: GPL-2.0

.. kernel-feat:: $srctree/Documentation/features arc

===================

ARC architecture

===================

.. toctree::

    :maxdepth: 1

    arc

    features

.. only::  subproject and html

   Indices

   =======

   * :ref:`genindex`