linux/Documentation/arm
Linus Torvalds e5ac320de1 ARM: SoC multiplatform code changes for v4.1
The changes here belong to two main platforms:
 
 - Atmel At91 is flipping the bit and going multiplatform. This includes some
   cleanups and removal of code, and the final flip of config dependencies
 
 - Shmobile has several platforms that are going multiplatform, but this
   branch also contains a bunch of cleanups that they weren't able to keep
   separate in a good way. THere's also a removal of one of their SoCs and the
   corresponding boards (sh7372 and mackerel).
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Merge tag 'armsoc-multiplatform' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc

Pull ARM SoC multiplatform code changes from Olof Johansson:
 "The changes here belong to two main platforms:

   - Atmel At91 is flipping the bit and going multiplatform.  This
     includes some cleanups and removal of code, and the final flip of
     config dependencies

   - Shmobile has several platforms that are going multiplatform, but
     this branch also contains a bunch of cleanups that they weren't
     able to keep separate in a good way.  THere's also a removal of one
     of their SoCs and the corresponding boards (sh7372 and mackerel)"

* tag 'armsoc-multiplatform' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc: (67 commits)
  ARM: at91/pm: move AT91_MEMCTRL_* to pm.h
  ARM: at91/pm: move the standby functions to pm.c
  ARM: at91: fix pm_suspend.S compilation when ARMv6 is selected
  ARM: at91: add a Kconfig dependency on multi-platform
  ARM: at91: drop AT91_TIMER_HZ
  ARM: at91: remove hardware.h
  ARM: at91: remove SoC headers
  ARM: at91: remove useless mach/cpu.h
  ARM: at91: remove unused headers
  ARM: at91: switch at91_dt_defconfig to multiplatform
  ARM: at91: switch to multiplatform
  ARM: shmobile: r8a7778: enable multiplatform target
  ARM: shmobile: bockw: add sound to DT
  ARM: shmobile: r8a7778: add sound to DT
  ARM: shmobile: bockw: add devices hooked up to i2c0 to DT
  DT: i2c: add trivial binding for OKI ML86V7667 video decoder
  ARM: shmobile: r8a7778: common clock framework CPG driver
  ARM: shmobile: bockw dts: set extal clock frequency
  ARM: shmobile: bockw dts: Move Ethernet node to BSC
  ARM: shmobile: r8a73a4: Remove legacy code
  ...
2015-04-22 09:20:15 -07:00
..
Atmel ARM: at91/Documentation: add a README for Atmel SoCs 2015-01-15 15:24:02 +01:00
Marvell Documentation: arm: update supported Marvell EBU processors 2015-03-04 15:35:43 +01:00
nwfpe Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
OMAP doc: Fix typo in doucmentations 2013-07-25 12:34:15 +02:00
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: S5PC100: no more support S5PC100 SoC 2014-07-13 07:35:11 +09:00
Samsung-S3C24XX ARM: SAMSUNG: remove unused DMA infrastructure 2015-01-24 13:09:54 +09:00
SH-Mobile Documentation: Remove ZBOOT MMC/SDHI utility and docs 2015-02-24 06:45:25 +09:00
SPEAr Viresh has moved 2012-06-20 14:39:36 -07:00
sti ARM: STi: Add STiH418 SoC support 2015-01-16 13:10:21 +01:00
sunxi ARM: sunxi: Add "allwinner,sun6i-a31s" to mach-sunxi 2015-01-05 09:50:39 +01:00
VFP [PATCH] kernel Doc/ URL corrections 2005-11-22 09:14:30 -08:00
00-INDEX ARM: Remove mach-msm and associated ARM architecture code 2015-03-27 11:31:02 -05:00
Booting Documentation: arm: Update for DT-only platforms 2015-02-27 14:54:55 -07:00
CCN.txt bus: ARM CCN PMU driver 2014-07-23 22:14:43 +02:00
cluster-pm-race-avoidance.txt ARM: mcpm: introduce helpers for platform coherency exit/setup 2013-04-24 10:37:00 -04:00
firmware.txt ARM: firmware: Introduce suspend and resume operations 2014-10-21 00:06:35 +09:00
Interrupts [ARM] Move include/asm-arm/arch-* to arch/arm/*/include/mach 2008-08-07 09:55:48 +01:00
IXP4xx Documentation/arm/IXP4xx fix a typo 2013-06-05 16:24:59 +02:00
kernel_mode_neon.txt ARM: 7825/1: document the use of NEON in kernel mode 2013-08-25 17:09:48 +01:00
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: expand fixmap region to 3MB 2014-10-16 14:38:52 -07:00
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: arm: Update for DT-only platforms 2015-02-27 14:54:55 -07:00
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
uefi.txt doc: arm: add UEFI support documentation 2014-04-30 19:57:01 +01:00
vlocks.txt ARM: mcpm: Add baremetal voting mutexes 2013-04-24 10:37:01 -04:00

			   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."

  For platforms that support device tree (DT), the machine selection is
  controlled at runtime by passing the device tree blob to the kernel.  At
  compile-time, support for the machine type must be selected.  This allows for
  a single multiplatform kernel build to be used for several machine types.

  For platforms that do not use device tree, this machine 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/>

  Note: Please do not register a machine type for DT-only platforms.  If your
  platform is DT-only, you do not need a registered machine type.

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