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- S3C2410 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 implemetation.
-
-
-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 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
--------
-
- See arch/arm/mach-s3c2410/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>
-
- The GPIO management functions are defined in the hardware
- header arch/arm/mach-s3c2410/include/mach/hardware.h which can be
- included by #include <mach/hardware.h>
-
- A useful amount of documentation can be found in the hardware
- header on how the GPIO functions (and others) work.
-
- Whilst a number of these functions do make some checks on what
- is passed to them, for speed of use, they may not always ensure
- that the user supplied data to them is correct.
-
-
-PIN Numbers
------------
-
- Each pin has an unique number associated with it in regs-gpio.h,
- 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
------------------
-
- The following function allows the configuration of a given pin to
- be changed.
-
- void s3c2410_gpio_cfgpin(unsigned int pin, unsigned int function);
-
- Eg:
-
- s3c2410_gpio_cfgpin(S3C2410_GPA(0), S3C2410_GPA0_ADDR0);
- s3c2410_gpio_cfgpin(S3C2410_GPE(8), S3C2410_GPE8_SDDAT1);
-
- 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
----------------------------------
-
- The current configuration of a pin can be read by using:
-
- s3c2410_gpio_getcfg(unsigned int pin);
-
- 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
-------------------------------
-
- 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 s3c2410_gpio_pullup(unsigned int pin, unsigned int to);
-
- 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
---------------------------
-
- The state of a pin can be read by using the function:
-
- unsigned int s3c2410_gpio_getpin(unsigned int 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
---------------------------
-
- The value an pin is outputing can be modified by using the following:
-
- void s3c2410_gpio_setpin(unsigned int pin, unsigned int to);
-
- 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
---------------------------------------------
-
- The following function can map the given pin number to an IRQ
- number to pass to the IRQ system.
-
- int s3c2410_gpio_getirq(unsigned int 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
--------
-
-
-Ben Dooks, 03 October 2004
-Copyright 2004 Ben Dooks, Simtec Electronics