Kernel-2.6.32-573.12.1.el6_Overview

        S3C24XX ARM Linux Overview
        ==========================

Introduction

The Samsung S3C24XX range of ARM9 System-on-Chip CPUs are supported
by the ‘s3c2410’ architecture of ARM Linux. Currently the S3C2410,
S3C2412, S3C2413, S3C2440, S3C2442 and S3C2443 devices are supported.

Support for the S3C2400 and S3C24A0 series are in progress.

Configuration

A generic S3C2410 configuration is provided, and can be used as the
default by make s3c2410_defconfig. This configuration has support
for all the machines, and the commonly used features on them.

Certain machines may have their own default configurations as well,
please check the machine specific documentation.

Layout

The core support files are located in the platform code contained in
arch/arm/plat-s3c24xx with headers in include/asm-arm/plat-s3c24xx.
This directory should be kept to items shared between the platform
code (arch/arm/plat-s3c24xx) and the arch/arm/mach-s3c24* code.

Each cpu has a directory with the support files for it, and the
machines that carry the device. For example S3C2410 is contained
in arch/arm/mach-s3c2410 and S3C2440 in arch/arm/mach-s3c2440

Register, kernel and platform data definitions are held in the
arch/arm/mach-s3c2410 directory./include/mach

arch/arm/plat-s3c24xx:

Files in here are either common to all the s3c24xx family,
or are common to only some of them with names to indicate this
status. The files that are not common to all are generally named
with the initial cpu they support in the series to ensure a short
name without any possibility of confusion with newer devices.

As an example, initially s3c244x would cover s3c2440 and s3c2442, but
with the s3c2443 which does not share many of the same drivers in
this directory, the name becomes invalid. We stick to s3c2440-
to indicate a driver that is s3c2440 and s3c2442 compatible.

This does mean that to find the status of any given SoC, a number
of directories may need to be searched.

Machines

The currently supported machines are as follows:

Simtec Electronics EB2410ITX (BAST)

A general purpose development board, see EB2410ITX.txt for further
details

Simtec Electronics IM2440D20 (Osiris)

CPU Module from Simtec Electronics, with a S3C2440A CPU, nand flash
and a PCMCIA controller.

Samsung SMDK2410

Samsung's own development board, geared for PDA work.

Samsung/Aiji SMDK2412

The S3C2412 version of the SMDK2440.

Samsung/Aiji SMDK2413

The S3C2412 version of the SMDK2440.

Samsung/Meritech SMDK2440

The S3C2440 compatible version of the SMDK2440, which has the
option of an S3C2440 or S3C2442 CPU module.

Thorcom VR1000

Custom embedded board

HP IPAQ 1940

Handheld (IPAQ), available in several varieties

HP iPAQ rx3715

S3C2440 based IPAQ, with a number of variations depending on
features shipped.

Acer N30

A S3C2410 based PDA from Acer.  There is a Wiki page at
http://handhelds.org/moin/moin.cgi/AcerN30Documentation .

AML M5900

American Microsystems' M5900

Nex Vision Nexcoder
Nex Vision Otom

Two machines by Nex Vision

Adding New Machines

The architecture has been designed to support as many machines as can
be configured for it in one kernel build, and any future additions
should keep this in mind before altering items outside of their own
machine files.

Machine definitions should be kept in linux/arch/arm/mach-s3c2410,
and there are a number of examples that can be looked at.

Read the kernel patch submission policies as well as the
Documentation/arm directory before submitting patches. The
ARM kernel series is managed by Russell King, and has a patch system
located at http://www.arm.linux.org.uk/developer/patches/
as well as mailing lists that can be found from the same site.

As a courtesy, please notify ben-linux@fluff.org of any new
machines or other modifications.

Any large scale modifications, or new drivers should be discussed
on the ARM kernel mailing list (linux-arm-kernel) before being
attempted. See http://www.arm.linux.org.uk/mailinglists/ for the
mailing list information.

I2C

The hardware I2C core in the CPU is supported in single master
mode, and can be configured via platform data.

RTC

Support for the onboard RTC unit, including alarm function.

This has recently been upgraded to use the new RTC core,
and the module has been renamed to rtc-s3c to fit in with
the new rtc naming scheme.

Watchdog

The onchip watchdog is available via the standard watchdog
interface.

NAND

The current kernels now have support for the s3c2410 NAND
controller. If there are any problems the latest linux-mtd
code can be found from http://www.linux-mtd.infradead.org/

For more information see Documentation/arm/Samsung-S3C24XX/NAND.txt

SD/MMC

The SD/MMC hardware pre S3C2443 is supported in the current
kernel, the driver is drivers/mmc/host/s3cmci.c and supports
1 and 4 bit SD or MMC cards.

The SDIO behaviour of this driver has not been fully tested. There is no
current support for hardware SDIO interrupts.

Serial

The s3c2410 serial driver provides support for the internal
serial ports. These devices appear as /dev/ttySAC0 through 3.

To create device nodes for these, use the following commands

mknod ttySAC0 c 204 64
mknod ttySAC1 c 204 65
mknod ttySAC2 c 204 66

GPIO

The core contains support for manipulating the GPIO, see the
documentation in GPIO.txt in the same directory as this file.

Newer kernels carry GPIOLIB, and support is being moved towards
this with some of the older support in line to be removed.

Clock Management

The core provides the interface defined in the header file
include/asm-arm/hardware/clock.h, to allow control over the
various clock units

Suspend to RAM

For boards that provide support for suspend to RAM, the
system can be placed into low power suspend.

See Suspend.txt for more information.

SPI

SPI drivers are available for both the in-built hardware
(although there is no DMA support yet) and a generic
GPIO based solution.

LEDs

There is support for GPIO based LEDs via a platform driver
in the LED subsystem.

Platform Data

Whenever a device has platform specific data that is specified
on a per-machine basis, care should be taken to ensure the
following:

1) that default data is not left in the device to confuse the
   driver if a machine does not set it at startup

2) the data should (if possible) be marked as __initdata,
   to ensure that the data is thrown away if the machine is
   not the one currently in use.

   The best way of doing this is to make a function that
   kmalloc()s an area of memory, and copies the __initdata
   and then sets the relevant device's platform data. Making
   the function `__init` takes care of ensuring it is discarded
   with the rest of the initialisation code

   static __init void s3c24xx_xxx_set_platdata(struct xxx_data *pd)
   {
       struct s3c2410_xxx_mach_info *npd;

   npd = kmalloc(sizeof(struct s3c2410_xxx_mach_info), GFP_KERNEL);
   if (npd) {
      memcpy(npd, pd, sizeof(struct s3c2410_xxx_mach_info));
      s3c_device_xxx.dev.platform_data = npd;
   } else {
          printk(KERN_ERR "no memory for xxx platform data\n");
   }
}

Note, since the code is marked as __init, it should not be
exported outside arch/arm/mach-s3c2410/, or exported to
modules via EXPORT_SYMBOL() and related functions.

Port Contributors

Ben Dooks (BJD)
Vincent Sanders
Herbert Potzl
Arnaud Patard (RTP)
Roc Wu
Klaus Fetscher
Dimitry Andric
Shannon Holland
Guillaume Gourat (NexVision)
Christer Weinigel (wingel) (Acer N30)
Lucas Correia Villa Real (S3C2400 port)

Document Author

Ben Dooks, (c) 2004-2005,2006 Simtec Electronics