1 files changed, 79 insertions, 2 deletions

diff --git a/Documentation/arm/Samsung-S3C24XX/GPIO.txt b/Documentation/arm/Samsung-S3C24XX/GPIO.txt
index 2af2cf39915f..816d6071669e 100644
--- a/Documentation/arm/Samsung-S3C24XX/GPIO.txt
+++ b/Documentation/arm/Samsung-S3C24XX/GPIO.txt
@@ -12,6 +12,8 @@ Introduction
   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 implemetation.
+
 
 GPIOLIB
 -------
@@ -24,8 +26,60 @@ GPIOLIB
   listed below will be removed (they may be marked as __deprecated
   in the near future).
 
-  - s3c2410_gpio_getpin
-  - s3c2410_gpio_setpin
+  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 exiting
+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() changs 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 replacable 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
@@ -54,6 +108,11 @@ PIN Numbers
   eg 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
 -----------------
@@ -71,6 +130,8 @@ Configuring a pin
    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.
 
+   The s3c_gpio_cfgpin() call is a functional replacement for this call.
+
 
 Reading the current configuration
 ---------------------------------
@@ -82,6 +143,9 @@ Reading the current configuration
   The return value will be from the same set of values which can be
   passed to s3c2410_gpio_cfgpin().
 
+  The s3c_gpio_getcfg() call should be a functional replacement for
+  this call.
+
 
 Configuring a pull-up resistor
 ------------------------------
@@ -95,6 +159,10 @@ Configuring a pull-up resistor
   Where the to value is zero to set the pull-up off, and 1 to enable
   the specified pull-up. Any other values are currently undefined.
 
+  The s3c_gpio_setpull() offers similar functionality, but with the
+  ability to encode whether the pull is up or down. Currently there
+  is no 'just on' state, so up or down must be selected.
+
 
 Getting the state of a PIN
 --------------------------
@@ -106,6 +174,9 @@ Getting the state of a PIN
   This will return either zero or non-zero. Do not count on this
   function returning 1 if the pin is set.
 
+  This call is now implemented by the relevant gpiolib calls, convert
+  your board or driver to use gpiolib.
+
 
 Setting the state of a PIN
 --------------------------
@@ -117,6 +188,9 @@ Setting the state of a PIN
   Which sets the given pin to the value. Use 0 to write 0, and 1 to
   set the output to 1.
 
+  This call is now implemented by the relevant gpiolib calls, convert
+  your board or driver to use gpiolib.
+
 
 Getting the IRQ number associated with a PIN
 --------------------------------------------
@@ -128,6 +202,9 @@ Getting the IRQ number associated with a PIN
 
   Note, not all pins have an IRQ.
 
+  This call is now implemented by the relevant gpiolib calls, convert
+  your board or driver to use gpiolib.
+
 
 Authour
 -------