Initial import

1 files changed, 171 insertions, 0 deletions

diff --git a/Documentation/arm/Samsung-S3C24XX/GPIO.txt b/Documentation/arm/Samsung-S3C24XX/GPIO.txt
new file mode 100644
index 000000000..0ebd7e224
--- /dev/null
+++ b/Documentation/arm/Samsung-S3C24XX/GPIO.txt
@@ -0,0 +1,171 @@
+			S3C24XX GPIO Control
+			====================
+
+Introduction
+------------
+
+  The s3c2410 kernel provides an interface to configure and
+  manipulate the state of the GPIO pins, and find out other
+  information about them.
+
+  There are a number of conditions attached to the configuration
+  of the s3c2410 GPIO system, please read the Samsung provided
+  data-sheet/users manual to find out the complete list.
+
+  See Documentation/arm/Samsung/GPIO.txt for the core implementation.
+
+
+GPIOLIB
+-------
+
+  With the event of the GPIOLIB in drivers/gpio, support for some
+  of the GPIO functions such as reading and writing a pin will
+  be removed in favour of this common access method.
+
+  Once all the extant drivers have been converted, the functions
+  listed below will be removed (they may be marked as __deprecated
+  in the near future).
+
+  The following functions now either have a s3c_ specific variant
+  or are merged into gpiolib. See the definitions in
+  arch/arm/plat-samsung/include/plat/gpio-cfg.h:
+
+  s3c2410_gpio_setpin()		gpio_set_value() or gpio_direction_output()
+  s3c2410_gpio_getpin()		gpio_get_value() or gpio_direction_input()
+  s3c2410_gpio_getirq()		gpio_to_irq()
+  s3c2410_gpio_cfgpin()		s3c_gpio_cfgpin()
+  s3c2410_gpio_getcfg()		s3c_gpio_getcfg()
+  s3c2410_gpio_pullup()		s3c_gpio_setpull()
+
+
+GPIOLIB conversion
+------------------
+
+If you need to convert your board or driver to use gpiolib from the phased
+out s3c2410 API, then here are some notes on the process.
+
+1) If your board is exclusively using an GPIO, say to control peripheral
+   power, then it will require to claim the gpio with gpio_request() before
+   it can use it.
+
+   It is recommended to check the return value, with at least WARN_ON()
+   during initialisation.
+
+2) The s3c2410_gpio_cfgpin() can be directly replaced with s3c_gpio_cfgpin()
+   as they have the same arguments, and can either take the pin specific
+   values, or the more generic special-function-number arguments.
+
+3) s3c2410_gpio_pullup() changes have the problem that whilst the
+   s3c2410_gpio_pullup(x, 1) can be easily translated to the
+   s3c_gpio_setpull(x, S3C_GPIO_PULL_NONE), the s3c2410_gpio_pullup(x, 0)
+   are not so easy.
+
+   The s3c2410_gpio_pullup(x, 0) case enables the pull-up (or in the case
+   of some of the devices, a pull-down) and as such the new API distinguishes
+   between the UP and DOWN case. There is currently no 'just turn on' setting
+   which may be required if this becomes a problem.
+
+4) s3c2410_gpio_setpin() can be replaced by gpio_set_value(), the old call
+   does not implicitly configure the relevant gpio to output. The gpio
+   direction should be changed before using gpio_set_value().
+
+5) s3c2410_gpio_getpin() is replaceable by gpio_get_value() if the pin
+   has been set to input. It is currently unknown what the behaviour is
+   when using gpio_get_value() on an output pin (s3c2410_gpio_getpin
+   would return the value the pin is supposed to be outputting).
+
+6) s3c2410_gpio_getirq() should be directly replaceable with the
+   gpio_to_irq() call.
+
+The s3c2410_gpio and gpio_ calls have always operated on the same gpio
+numberspace, so there is no problem with converting the gpio numbering
+between the calls.
+
+
+Headers
+-------
+
+  See arch/arm/mach-s3c24xx/include/mach/regs-gpio.h for the list
+  of GPIO pins, and the configuration values for them. This
+  is included by using #include <mach/regs-gpio.h>
+
+
+PIN Numbers
+-----------
+
+  Each pin has an unique number associated with it in regs-gpio.h,
+  e.g. S3C2410_GPA(0) or S3C2410_GPF(1). These defines are used to tell
+  the GPIO functions which pin is to be used.
+
+  With the conversion to gpiolib, there is no longer a direct conversion
+  from gpio pin number to register base address as in earlier kernels. This
+  is due to the number space required for newer SoCs where the later
+  GPIOs are not contiguous.
+
+
+Configuring a pin
+-----------------
+
+  The following function allows the configuration of a given pin to
+  be changed.
+
+    void s3c_gpio_cfgpin(unsigned int pin, unsigned int function);
+
+  e.g.:
+
+     s3c_gpio_cfgpin(S3C2410_GPA(0), S3C_GPIO_SFN(1));
+     s3c_gpio_cfgpin(S3C2410_GPE(8), S3C_GPIO_SFN(2));
+
+   which would turn GPA(0) into the lowest Address line A0, and set
+   GPE(8) to be connected to the SDIO/MMC controller's SDDAT1 line.
+
+
+Reading the current configuration
+---------------------------------
+
+  The current configuration of a pin can be read by using standard
+  gpiolib function:
+
+  s3c_gpio_getcfg(unsigned int pin);
+
+  The return value will be from the same set of values which can be
+  passed to s3c_gpio_cfgpin().
+
+
+Configuring a pull-up resistor
+------------------------------
+
+  A large proportion of the GPIO pins on the S3C2410 can have weak
+  pull-up resistors enabled. This can be configured by the following
+  function:
+
+    void s3c_gpio_setpull(unsigned int pin, unsigned int to);
+
+  Where the to value is S3C_GPIO_PULL_NONE to set the pull-up off,
+  and S3C_GPIO_PULL_UP to enable the specified pull-up. Any other
+  values are currently undefined.
+
+
+Getting and setting the state of a PIN
+--------------------------------------
+
+  These calls are now implemented by the relevant gpiolib calls, convert
+  your board or driver to use gpiolib.
+
+
+Getting the IRQ number associated with a PIN
+--------------------------------------------
+
+  A standard gpiolib function can map the given pin number to an IRQ
+  number to pass to the IRQ system.
+
+   int gpio_to_irq(unsigned int pin);
+
+  Note, not all pins have an IRQ.
+
+
+Author
+-------
+
+Ben Dooks, 03 October 2004
+Copyright 2004 Ben Dooks, Simtec Electronics