312 lines
8.3 KiB
ReStructuredText
312 lines
8.3 KiB
ReStructuredText
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==========================
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S3C24XX ARM Linux Overview
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==========================
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Introduction
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------------
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The Samsung S3C24XX range of ARM9 System-on-Chip CPUs are supported
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by the 's3c2410' architecture of ARM Linux. Currently the S3C2410,
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S3C2412, S3C2413, S3C2416, S3C2440, S3C2442, S3C2443 and S3C2450 devices
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are supported.
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Support for the S3C2400 and S3C24A0 series was never completed and the
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corresponding code has been removed after a while. If someone wishes to
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revive this effort, partial support can be retrieved from earlier Linux
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versions.
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The S3C2416 and S3C2450 devices are very similar and S3C2450 support is
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included under the arch/arm/mach-s3c directory. Note, while core
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support for these SoCs is in, work on some of the extra peripherals
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and extra interrupts is still ongoing.
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Configuration
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-------------
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A generic S3C2410 configuration is provided, and can be used as the
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default by `make s3c2410_defconfig`. This configuration has support
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for all the machines, and the commonly used features on them.
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Certain machines may have their own default configurations as well,
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please check the machine specific documentation.
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Layout
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------
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The core support files, register, kernel and paltform data are located in the
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platform code contained in arch/arm/mach-s3c with headers in
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arch/arm/mach-s3c/include
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arch/arm/mach-s3c:
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Files in here are either common to all the s3c24xx family,
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or are common to only some of them with names to indicate this
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status. The files that are not common to all are generally named
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with the initial cpu they support in the series to ensure a short
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name without any possibility of confusion with newer devices.
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As an example, initially s3c244x would cover s3c2440 and s3c2442, but
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with the s3c2443 which does not share many of the same drivers in
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this directory, the name becomes invalid. We stick to s3c2440-<x>
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to indicate a driver that is s3c2440 and s3c2442 compatible.
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This does mean that to find the status of any given SoC, a number
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of directories may need to be searched.
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Machines
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--------
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The currently supported machines are as follows:
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Simtec Electronics EB2410ITX (BAST)
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A general purpose development board, see EB2410ITX.txt for further
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details
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Simtec Electronics IM2440D20 (Osiris)
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CPU Module from Simtec Electronics, with a S3C2440A CPU, nand flash
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and a PCMCIA controller.
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Samsung SMDK2410
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Samsung's own development board, geared for PDA work.
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Samsung/Aiji SMDK2412
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The S3C2412 version of the SMDK2440.
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Samsung/Aiji SMDK2413
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The S3C2412 version of the SMDK2440.
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Samsung/Meritech SMDK2440
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The S3C2440 compatible version of the SMDK2440, which has the
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option of an S3C2440 or S3C2442 CPU module.
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Thorcom VR1000
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Custom embedded board
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HP IPAQ 1940
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Handheld (IPAQ), available in several varieties
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HP iPAQ rx3715
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S3C2440 based IPAQ, with a number of variations depending on
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features shipped.
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Acer N30
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A S3C2410 based PDA from Acer. There is a Wiki page at
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http://handhelds.org/moin/moin.cgi/AcerN30Documentation .
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AML M5900
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American Microsystems' M5900
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Nex Vision Nexcoder
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Nex Vision Otom
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Two machines by Nex Vision
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Adding New Machines
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-------------------
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The architecture has been designed to support as many machines as can
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be configured for it in one kernel build, and any future additions
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should keep this in mind before altering items outside of their own
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machine files.
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Machine definitions should be kept in arch/arm/mach-s3c,
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and there are a number of examples that can be looked at.
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Read the kernel patch submission policies as well as the
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Documentation/arm directory before submitting patches. The
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ARM kernel series is managed by Russell King, and has a patch system
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located at http://www.arm.linux.org.uk/developer/patches/
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as well as mailing lists that can be found from the same site.
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As a courtesy, please notify <ben-linux@fluff.org> of any new
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machines or other modifications.
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Any large scale modifications, or new drivers should be discussed
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on the ARM kernel mailing list (linux-arm-kernel) before being
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attempted. See http://www.arm.linux.org.uk/mailinglists/ for the
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mailing list information.
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I2C
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---
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The hardware I2C core in the CPU is supported in single master
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mode, and can be configured via platform data.
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RTC
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---
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Support for the onboard RTC unit, including alarm function.
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This has recently been upgraded to use the new RTC core,
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and the module has been renamed to rtc-s3c to fit in with
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the new rtc naming scheme.
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Watchdog
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--------
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The onchip watchdog is available via the standard watchdog
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interface.
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NAND
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----
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The current kernels now have support for the s3c2410 NAND
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controller. If there are any problems the latest linux-mtd
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code can be found from http://www.linux-mtd.infradead.org/
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For more information see Documentation/arm/samsung-s3c24xx/nand.rst
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SD/MMC
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------
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The SD/MMC hardware pre S3C2443 is supported in the current
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kernel, the driver is drivers/mmc/host/s3cmci.c and supports
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1 and 4 bit SD or MMC cards.
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The SDIO behaviour of this driver has not been fully tested. There is no
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current support for hardware SDIO interrupts.
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Serial
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------
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The s3c2410 serial driver provides support for the internal
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serial ports. These devices appear as /dev/ttySAC0 through 3.
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To create device nodes for these, use the following commands
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mknod ttySAC0 c 204 64
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mknod ttySAC1 c 204 65
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mknod ttySAC2 c 204 66
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GPIO
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----
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The core contains support for manipulating the GPIO, see the
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documentation in GPIO.txt in the same directory as this file.
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Newer kernels carry GPIOLIB, and support is being moved towards
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this with some of the older support in line to be removed.
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As of v2.6.34, the move towards using gpiolib support is almost
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complete, and very little of the old calls are left.
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See Documentation/arm/samsung-s3c24xx/gpio.rst for the S3C24XX specific
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support and Documentation/arm/samsung/gpio.rst for the core Samsung
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implementation.
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Clock Management
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----------------
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The core provides the interface defined in the header file
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include/asm-arm/hardware/clock.h, to allow control over the
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various clock units
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Suspend to RAM
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--------------
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For boards that provide support for suspend to RAM, the
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system can be placed into low power suspend.
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See Suspend.txt for more information.
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SPI
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---
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SPI drivers are available for both the in-built hardware
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(although there is no DMA support yet) and a generic
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GPIO based solution.
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LEDs
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----
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There is support for GPIO based LEDs via a platform driver
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in the LED subsystem.
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Platform Data
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-------------
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Whenever a device has platform specific data that is specified
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on a per-machine basis, care should be taken to ensure the
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following:
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1) that default data is not left in the device to confuse the
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driver if a machine does not set it at startup
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2) the data should (if possible) be marked as __initdata,
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to ensure that the data is thrown away if the machine is
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not the one currently in use.
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The best way of doing this is to make a function that
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kmalloc()s an area of memory, and copies the __initdata
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and then sets the relevant device's platform data. Making
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the function `__init` takes care of ensuring it is discarded
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with the rest of the initialisation code::
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static __init void s3c24xx_xxx_set_platdata(struct xxx_data *pd)
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{
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struct s3c2410_xxx_mach_info *npd;
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npd = kmalloc(sizeof(struct s3c2410_xxx_mach_info), GFP_KERNEL);
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if (npd) {
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memcpy(npd, pd, sizeof(struct s3c2410_xxx_mach_info));
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s3c_device_xxx.dev.platform_data = npd;
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} else {
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printk(KERN_ERR "no memory for xxx platform data\n");
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}
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}
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Note, since the code is marked as __init, it should not be
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exported outside arch/arm/mach-s3c/, or exported to
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modules via EXPORT_SYMBOL() and related functions.
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Port Contributors
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-----------------
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Ben Dooks (BJD)
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Vincent Sanders
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Herbert Potzl
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Arnaud Patard (RTP)
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Roc Wu
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Klaus Fetscher
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Dimitry Andric
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Shannon Holland
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Guillaume Gourat (NexVision)
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Christer Weinigel (wingel) (Acer N30)
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Lucas Correia Villa Real (S3C2400 port)
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Document Author
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---------------
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Ben Dooks, Copyright 2004-2006 Simtec Electronics
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