cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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overview.rst (8486B)


      1==========================
      2S3C24XX ARM Linux Overview
      3==========================
      4
      5
      6
      7Introduction
      8------------
      9
     10  The Samsung S3C24XX range of ARM9 System-on-Chip CPUs are supported
     11  by the 's3c2410' architecture of ARM Linux. Currently the S3C2410,
     12  S3C2412, S3C2413, S3C2416, S3C2440, S3C2442, S3C2443 and S3C2450 devices
     13  are supported.
     14
     15  Support for the S3C2400 and S3C24A0 series was never completed and the
     16  corresponding code has been removed after a while.  If someone wishes to
     17  revive this effort, partial support can be retrieved from earlier Linux
     18  versions.
     19
     20  The S3C2416 and S3C2450 devices are very similar and S3C2450 support is
     21  included under the arch/arm/mach-s3c directory. Note, while core
     22  support for these SoCs is in, work on some of the extra peripherals
     23  and extra interrupts is still ongoing.
     24
     25
     26Configuration
     27-------------
     28
     29  A generic S3C2410 configuration is provided, and can be used as the
     30  default by `make s3c2410_defconfig`. This configuration has support
     31  for all the machines, and the commonly used features on them.
     32
     33  Certain machines may have their own default configurations as well,
     34  please check the machine specific documentation.
     35
     36
     37Layout
     38------
     39
     40  The core support files, register, kernel and paltform data are located in the
     41  platform code contained in arch/arm/mach-s3c with headers in
     42  arch/arm/mach-s3c/include
     43
     44arch/arm/mach-s3c:
     45
     46  Files in here are either common to all the s3c24xx family,
     47  or are common to only some of them with names to indicate this
     48  status. The files that are not common to all are generally named
     49  with the initial cpu they support in the series to ensure a short
     50  name without any possibility of confusion with newer devices.
     51
     52  As an example, initially s3c244x would cover s3c2440 and s3c2442, but
     53  with the s3c2443 which does not share many of the same drivers in
     54  this directory, the name becomes invalid. We stick to s3c2440-<x>
     55  to indicate a driver that is s3c2440 and s3c2442 compatible.
     56
     57  This does mean that to find the status of any given SoC, a number
     58  of directories may need to be searched.
     59
     60
     61Machines
     62--------
     63
     64  The currently supported machines are as follows:
     65
     66  Simtec Electronics EB2410ITX (BAST)
     67
     68    A general purpose development board, see EB2410ITX.txt for further
     69    details
     70
     71  Simtec Electronics IM2440D20 (Osiris)
     72
     73    CPU Module from Simtec Electronics, with a S3C2440A CPU, nand flash
     74    and a PCMCIA controller.
     75
     76  Samsung SMDK2410
     77
     78    Samsung's own development board, geared for PDA work.
     79
     80  Samsung/Aiji SMDK2412
     81
     82    The S3C2412 version of the SMDK2440.
     83
     84  Samsung/Aiji SMDK2413
     85
     86    The S3C2412 version of the SMDK2440.
     87
     88  Samsung/Meritech SMDK2440
     89
     90    The S3C2440 compatible version of the SMDK2440, which has the
     91    option of an S3C2440 or S3C2442 CPU module.
     92
     93  Thorcom VR1000
     94
     95    Custom embedded board
     96
     97  HP IPAQ 1940
     98
     99    Handheld (IPAQ), available in several varieties
    100
    101  HP iPAQ rx3715
    102
    103    S3C2440 based IPAQ, with a number of variations depending on
    104    features shipped.
    105
    106  Acer N30
    107
    108    A S3C2410 based PDA from Acer.  There is a Wiki page at
    109    http://handhelds.org/moin/moin.cgi/AcerN30Documentation .
    110
    111  AML M5900
    112
    113    American Microsystems' M5900
    114
    115  Nex Vision Nexcoder
    116  Nex Vision Otom
    117
    118    Two machines by Nex Vision
    119
    120
    121Adding New Machines
    122-------------------
    123
    124  The architecture has been designed to support as many machines as can
    125  be configured for it in one kernel build, and any future additions
    126  should keep this in mind before altering items outside of their own
    127  machine files.
    128
    129  Machine definitions should be kept in arch/arm/mach-s3c,
    130  and there are a number of examples that can be looked at.
    131
    132  Read the kernel patch submission policies as well as the
    133  Documentation/arm directory before submitting patches. The
    134  ARM kernel series is managed by Russell King, and has a patch system
    135  located at http://www.arm.linux.org.uk/developer/patches/
    136  as well as mailing lists that can be found from the same site.
    137
    138  As a courtesy, please notify <ben-linux@fluff.org> of any new
    139  machines or other modifications.
    140
    141  Any large scale modifications, or new drivers should be discussed
    142  on the ARM kernel mailing list (linux-arm-kernel) before being
    143  attempted. See http://www.arm.linux.org.uk/mailinglists/ for the
    144  mailing list information.
    145
    146
    147I2C
    148---
    149
    150  The hardware I2C core in the CPU is supported in single master
    151  mode, and can be configured via platform data.
    152
    153
    154RTC
    155---
    156
    157  Support for the onboard RTC unit, including alarm function.
    158
    159  This has recently been upgraded to use the new RTC core,
    160  and the module has been renamed to rtc-s3c to fit in with
    161  the new rtc naming scheme.
    162
    163
    164Watchdog
    165--------
    166
    167  The onchip watchdog is available via the standard watchdog
    168  interface.
    169
    170
    171NAND
    172----
    173
    174  The current kernels now have support for the s3c2410 NAND
    175  controller. If there are any problems the latest linux-mtd
    176  code can be found from http://www.linux-mtd.infradead.org/
    177
    178  For more information see Documentation/arm/samsung-s3c24xx/nand.rst
    179
    180
    181SD/MMC
    182------
    183
    184  The SD/MMC hardware pre S3C2443 is supported in the current
    185  kernel, the driver is drivers/mmc/host/s3cmci.c and supports
    186  1 and 4 bit SD or MMC cards.
    187
    188  The SDIO behaviour of this driver has not been fully tested. There is no
    189  current support for hardware SDIO interrupts.
    190
    191
    192Serial
    193------
    194
    195  The s3c2410 serial driver provides support for the internal
    196  serial ports. These devices appear as /dev/ttySAC0 through 3.
    197
    198  To create device nodes for these, use the following commands
    199
    200    mknod ttySAC0 c 204 64
    201    mknod ttySAC1 c 204 65
    202    mknod ttySAC2 c 204 66
    203
    204
    205GPIO
    206----
    207
    208  The core contains support for manipulating the GPIO, see the
    209  documentation in GPIO.txt in the same directory as this file.
    210
    211  Newer kernels carry GPIOLIB, and support is being moved towards
    212  this with some of the older support in line to be removed.
    213
    214  As of v2.6.34, the move towards using gpiolib support is almost
    215  complete, and very little of the old calls are left.
    216
    217  See Documentation/arm/samsung-s3c24xx/gpio.rst for the S3C24XX specific
    218  support and Documentation/arm/samsung/gpio.rst for the core Samsung
    219  implementation.
    220
    221
    222Clock Management
    223----------------
    224
    225  The core provides the interface defined in the header file
    226  include/asm-arm/hardware/clock.h, to allow control over the
    227  various clock units
    228
    229
    230Suspend to RAM
    231--------------
    232
    233  For boards that provide support for suspend to RAM, the
    234  system can be placed into low power suspend.
    235
    236  See Suspend.txt for more information.
    237
    238
    239SPI
    240---
    241
    242  SPI drivers are available for both the in-built hardware
    243  (although there is no DMA support yet) and a generic
    244  GPIO based solution.
    245
    246
    247LEDs
    248----
    249
    250  There is support for GPIO based LEDs via a platform driver
    251  in the LED subsystem.
    252
    253
    254Platform Data
    255-------------
    256
    257  Whenever a device has platform specific data that is specified
    258  on a per-machine basis, care should be taken to ensure the
    259  following:
    260
    261    1) that default data is not left in the device to confuse the
    262       driver if a machine does not set it at startup
    263
    264    2) the data should (if possible) be marked as __initdata,
    265       to ensure that the data is thrown away if the machine is
    266       not the one currently in use.
    267
    268       The best way of doing this is to make a function that
    269       kmalloc()s an area of memory, and copies the __initdata
    270       and then sets the relevant device's platform data. Making
    271       the function `__init` takes care of ensuring it is discarded
    272       with the rest of the initialisation code::
    273
    274         static __init void s3c24xx_xxx_set_platdata(struct xxx_data *pd)
    275         {
    276             struct s3c2410_xxx_mach_info *npd;
    277
    278	   npd = kmalloc(sizeof(struct s3c2410_xxx_mach_info), GFP_KERNEL);
    279	   if (npd) {
    280	      memcpy(npd, pd, sizeof(struct s3c2410_xxx_mach_info));
    281	      s3c_device_xxx.dev.platform_data = npd;
    282	   } else {
    283                printk(KERN_ERR "no memory for xxx platform data\n");
    284	   }
    285	}
    286
    287	Note, since the code is marked as __init, it should not be
    288	exported outside arch/arm/mach-s3c/, or exported to
    289	modules via EXPORT_SYMBOL() and related functions.
    290
    291
    292Port Contributors
    293-----------------
    294
    295  Ben Dooks (BJD)
    296  Vincent Sanders
    297  Herbert Potzl
    298  Arnaud Patard (RTP)
    299  Roc Wu
    300  Klaus Fetscher
    301  Dimitry Andric
    302  Shannon Holland
    303  Guillaume Gourat (NexVision)
    304  Christer Weinigel (wingel) (Acer N30)
    305  Lucas Correia Villa Real (S3C2400 port)
    306
    307
    308Document Author
    309---------------
    310
    311Ben Dooks, Copyright 2004-2006 Simtec Electronics