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, S3C2416, S3C2440, S3C2442, S3C2443 and S3C2450 devices
are supported.
Support for the S3C2400 and S3C24A0 series was never completed and the
corresponding code has been removed after a while. If someone wishes to
revive this effort, partial support can be retrieved from earlier Linux
versions.
The S3C2416 and S3C2450 devices are very similar and S3C2450 support is
included under the arch/arm/mach-s3c2416 directory. Note, whilst core
support for these SoCs is in, work on some of the extra peripherals
and extra interrupts is still ongoing.
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-<x>
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.
As of v2.6.34, the move towards using gpiolib support is almost
complete, and very little of the old calls are left.
See Documentation/arm/Samsung-S3C24XX/GPIO.txt for the S3C24XX specific
support and Documentation/arm/Samsung/GPIO.txt for the core Samsung
implementation.
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, Copyright 2004-2006 Simtec Electronics