linux/Documentation/arm
Linus Torvalds b324c67d48 arm-soc: device tree conversions, part 1
The spear3xx, lpc32xx, shmobile and mmp platforms are joining the game of
 booting using device trees, which is a great step forward for them. at91
 and spear have pretty much completed this process with a huge amount of
 work being put into at91. The other platforms are continuing the process.
 
 We finally start to see the payback on this investment, as new machines
 are getting supported purely by adding a .dts source file that can be
 completely independent of the kernel source.
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1.4.11 (GNU/Linux)
 
 iQIcBAABAgAGBQJPueqRAAoJEIwa5zzehBx3AYkP/ibDGGd0qp1gxnxPYowliXcp
 lrWP8KB2PVcX/041jwpvsWeHzWT+Gm39ryBfz2L3pq/RiuU0jPPwChKgy1iglE8X
 6Rq6sPWkXoDRtyeCuoiaxf1AYuzzAVdzZ0HlPO93tSKgo5eeyZRC5OeebAnrLDCE
 SDi8gZx2mm9+j2Dz46gq8QluyswMMbke3fHHHaHUlcP9fKIvFWvEfsn5j+YQ9bSw
 DrSIqGOzv6Emn7F6yhFQqxmk86KLnaXDVpAWgjVDhzaPv0rcTzloN6D2Ie2e5Vev
 BiRM1zvWn2d9kDk7gpm0t67nguYxsCBl1GNCP1brrncGwt15S10JimYlRhYW+B7u
 qgJqMPko3OnONvyl6e8qgIa2M5N4K/mo1i/jfOwFw3+KfUjXqLeio53Ysr4a6tsM
 Ev3bEsofNJKA0dlMcVzr7ntL087B6Y8mY3oJsVZji5M0KVfx1Jfn+X1W+l/2KD1H
 XWhJrCGa1HlbtSnrD+E91VHGC3M4sEXbbTljMAjHImlU9dGXmmbRMNsqNwkF6qFj
 EO2HnFvdN1oK+zEmeAttR1JHxfMdPFnTfmpUf3AiVSjGO//Wltelqx8ibA2Smn7S
 xXmzqX/HMhIOYCh81FdvzsK4qRYU5QyOsEJB4G0UjBZ66M1A3T/+vPpWuKsw5bUb
 qbnxaaXNsaZjWbbSSrZ4
 =7DYv
 -----END PGP SIGNATURE-----

Merge tag 'dt' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc

Pull device tree conversions for arm-soc, part 1, from Olof Johansson:
 "The spear3xx, lpc32xx, shmobile and mmp platforms are joining the game
  of booting using device trees, which is a great step forward for them.
  at91 and spear have pretty much completed this process with a huge
  amount of work being put into at91.  The other platforms are
  continuing the process.

  We finally start to see the payback on this investment, as new
  machines are getting supported purely by adding a .dts source file
  that can be completely independent of the kernel source."

Fix up trivial conflict in arch/arm/Kconfig

* tag 'dt' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc: (83 commits)
  ARM: at91: Add ADC driver to at91sam9260/at91sam9g20 dtsi files
  arm/dts: omap4-panda: Add LEDs support
  arm/dts: omap4-sdp: Add LEDs support
  arm/dts: twl4030: Add twl4030-gpio node
  OMAP4: devices: Do not create mcpdm device if the dtb has been provided
  OMAP4: devices: Do not create dmic device if the dtb has been provided
  Documentation: update docs for mmp dt
  ARM: dts: refresh dts file for arch mmp
  ARM: mmp: support pxa910 with device tree
  ARM: mmp: support mmp2 with device tree
  gpio: pxa: parse gpio from DTS file
  ARM: mmp: support DT in timer
  ARM: mmp: support DT in irq
  ARM: mmp: append CONFIG_MACH_MMP2_DT
  ARM: mmp: fix build issue on mmp with device tree
  ARM: ux500: Enable PRCMU Timer 4 (clocksource) for Device Tree
  ARM: ux500: Disable SMSC911x platform code registration when DT is enabled
  ARM: ux500: Fork cpu-db8500 platform_devs for sequential DT enablement
  ARM: ux500: Do not attempt to register non-existent i2c devices on Snowball
  ARM: SPEAr3xx: Correct keyboard data passed from DT
  ...
2012-05-22 09:30:52 -07:00
..
msm msm: documentation: add gpiomux documentation. 2010-10-06 09:01:16 -07:00
nwfpe Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
OMAP omap: opp: add OMAP3 OPP table data and common init 2010-12-21 14:30:40 -08:00
pxa [ARM] pxa: add document on the MFP design and how to use it 2008-12-29 17:58:18 +08:00
SA1100 Doc: Fix spelling 2010-08-10 14:22:39 +02:00
Samsung ARM: S5P6442: Removing ARCH_S5P6442 2011-05-12 08:10:53 +09:00
Samsung-S3C24XX ARM: mach-s3c2400: delete 2011-07-18 10:59:26 -04:00
SH-Mobile ARM: 6886/1: mmc, Add zboot from eSD support for SuperH Mobile ARM 2011-06-29 10:00:52 +01:00
SPEAr ARM: SPEAr3xx: Add device-tree support to SPEAr3xx architecture 2012-04-22 22:41:35 +02:00
VFP [PATCH] kernel Doc/ URL corrections 2005-11-22 09:14:30 -08:00
00-INDEX ARM: remove ixp23xx and ixp2000 platforms 2012-04-06 08:26:18 -05:00
Booting ARM: 6999/1: head, zImage: Always Enter the kernel in ARM state 2011-07-19 12:00:53 +01:00
Interrupts [ARM] Move include/asm-arm/arch-* to arch/arm/*/include/mach 2008-08-07 09:55:48 +01:00
IXP4xx Fix common misspellings 2011-03-31 11:26:23 -03:00
kernel_user_helpers.txt Documentation: Fix multiple typo in Documentation 2012-03-07 16:08:24 +01:00
mem_alignment [ARM] 5348/1: fix documentation wrt location of the alignment trap interface 2008-12-15 10:34:58 +00:00
memory.txt ARM: move iotable mappings within the vmalloc region 2011-11-26 19:21:26 -05:00
Netwinder Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
Porting Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
README Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
Setup Fix simple typos 2006-03-24 18:13:37 +01:00
swp_emulation ARM: 6396/1: Add SWP/SWPB emulation for ARMv7 processors 2010-11-04 15:45:24 +00:00
tcm.txt ARM: 6225/1: make TCM allocation static and common for all archs 2010-07-27 10:42:38 +01:00

			   ARM Linux 2.6
			   =============

    Please check <ftp://ftp.arm.linux.org.uk/pub/armlinux> for
    updates.

Compilation of kernel
---------------------

  In order to compile ARM Linux, you will need a compiler capable of
  generating ARM ELF code with GNU extensions.  GCC 3.3 is known to be
  a good compiler.  Fortunately, you needn't guess.  The kernel will report
  an error if your compiler is a recognized offender.

  To build ARM Linux natively, you shouldn't have to alter the ARCH = line
  in the top level Makefile.  However, if you don't have the ARM Linux ELF
  tools installed as default, then you should change the CROSS_COMPILE
  line as detailed below.

  If you wish to cross-compile, then alter the following lines in the top
  level make file:

    ARCH = <whatever>
	with
    ARCH = arm

	and

    CROSS_COMPILE=
	to
    CROSS_COMPILE=<your-path-to-your-compiler-without-gcc>
	eg.
    CROSS_COMPILE=arm-linux-

  Do a 'make config', followed by 'make Image' to build the kernel 
  (arch/arm/boot/Image).  A compressed image can be built by doing a 
  'make zImage' instead of 'make Image'.


Bug reports etc
---------------

  Please send patches to the patch system.  For more information, see
  http://www.arm.linux.org.uk/developer/patches/info.php Always include some
  explanation as to what the patch does and why it is needed.

  Bug reports should be sent to linux-arm-kernel@lists.arm.linux.org.uk,
  or submitted through the web form at
  http://www.arm.linux.org.uk/developer/ 

  When sending bug reports, please ensure that they contain all relevant
  information, eg. the kernel messages that were printed before/during
  the problem, what you were doing, etc.


Include files
-------------

  Several new include directories have been created under include/asm-arm,
  which are there to reduce the clutter in the top-level directory.  These
  directories, and their purpose is listed below:

   arch-*	machine/platform specific header files
   hardware	driver-internal ARM specific data structures/definitions
   mach		descriptions of generic ARM to specific machine interfaces
   proc-*	processor dependent header files (currently only two
		categories)


Machine/Platform support
------------------------

  The ARM tree contains support for a lot of different machine types.  To
  continue supporting these differences, it has become necessary to split
  machine-specific parts by directory.  For this, the machine category is
  used to select which directories and files get included (we will use
  $(MACHINE) to refer to the category)

  To this end, we now have arch/arm/mach-$(MACHINE) directories which are
  designed to house the non-driver files for a particular machine (eg, PCI,
  memory management, architecture definitions etc).  For all future
  machines, there should be a corresponding arch/arm/mach-$(MACHINE)/include/mach
  directory.


Modules
-------

  Although modularisation is supported (and required for the FP emulator),
  each module on an ARM2/ARM250/ARM3 machine when is loaded will take
  memory up to the next 32k boundary due to the size of the pages.
  Therefore, is modularisation on these machines really worth it?

  However, ARM6 and up machines allow modules to take multiples of 4k, and
  as such Acorn RiscPCs and other architectures using these processors can
  make good use of modularisation.


ADFS Image files
----------------

  You can access image files on your ADFS partitions by mounting the ADFS
  partition, and then using the loopback device driver.  You must have
  losetup installed.

  Please note that the PCEmulator DOS partitions have a partition table at
  the start, and as such, you will have to give '-o offset' to losetup.


Request to developers
---------------------

  When writing device drivers which include a separate assembler file, please
  include it in with the C file, and not the arch/arm/lib directory.  This
  allows the driver to be compiled as a loadable module without requiring
  half the code to be compiled into the kernel image.

  In general, try to avoid using assembler unless it is really necessary.  It
  makes drivers far less easy to port to other hardware.


ST506 hard drives
-----------------

  The ST506 hard drive controllers seem to be working fine (if a little
  slowly).  At the moment they will only work off the controllers on an
  A4x0's motherboard, but for it to work off a Podule just requires
  someone with a podule to add the addresses for the IRQ mask and the
  HDC base to the source.

  As of 31/3/96 it works with two drives (you should get the ADFS
  *configure harddrive set to 2). I've got an internal 20MB and a great
  big external 5.25" FH 64MB drive (who could ever want more :-) ).

  I've just got 240K/s off it (a dd with bs=128k); thats about half of what
  RiscOS gets; but it's a heck of a lot better than the 50K/s I was getting
  last week :-)

  Known bug: Drive data errors can cause a hang; including cases where
  the controller has fixed the error using ECC. (Possibly ONLY
  in that case...hmm).


1772 Floppy
-----------
  This also seems to work OK, but hasn't been stressed much lately.  It
  hasn't got any code for disc change detection in there at the moment which
  could be a bit of a problem!  Suggestions on the correct way to do this
  are welcome.


CONFIG_MACH_ and CONFIG_ARCH_
-----------------------------
  A change was made in 2003 to the macro names for new machines.
  Historically, CONFIG_ARCH_ was used for the bonafide architecture,
  e.g. SA1100, as well as implementations of the architecture,
  e.g. Assabet.  It was decided to change the implementation macros
  to read CONFIG_MACH_ for clarity.  Moreover, a retroactive fixup has
  not been made because it would complicate patching.

  Previous registrations may be found online.

    <http://www.arm.linux.org.uk/developer/machines/>

Kernel entry (head.S)
--------------------------
  The initial entry into the kernel is via head.S, which uses machine
  independent code.  The machine is selected by the value of 'r1' on
  entry, which must be kept unique.

  Due to the large number of machines which the ARM port of Linux provides
  for, we have a method to manage this which ensures that we don't end up
  duplicating large amounts of code.

  We group machine (or platform) support code into machine classes.  A
  class typically based around one or more system on a chip devices, and
  acts as a natural container around the actual implementations.  These
  classes are given directories - arch/arm/mach-<class> and
  arch/arm/mach-<class> - which contain the source files to/include/mach
  support the machine class.  This directories also contain any machine
  specific supporting code.

  For example, the SA1100 class is based upon the SA1100 and SA1110 SoC
  devices, and contains the code to support the way the on-board and off-
  board devices are used, or the device is setup, and provides that
  machine specific "personality."

  This fine-grained machine specific selection is controlled by the machine
  type ID, which acts both as a run-time and a compile-time code selection
  method.

  You can register a new machine via the web site at:

    <http://www.arm.linux.org.uk/developer/machines/>

---
Russell King (15/03/2004)