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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-16 12:21:41 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-16 12:21:41 -0700 |
commit | c309b6f24222246c18a8b65d3950e6e755440865 (patch) | |
tree | 11893170f5c246bb0dee8066e85878af04162ab0 /Documentation/arm/samsung-s3c24xx/gpio.rst | |
parent | 3e859477a1db52a0435d06a55fdb54f62d69c292 (diff) | |
parent | 168869492e7009b6861b615f1d030c99bc805e83 (diff) | |
download | linux-stable-c309b6f24222246c18a8b65d3950e6e755440865.tar.gz linux-stable-c309b6f24222246c18a8b65d3950e6e755440865.tar.bz2 linux-stable-c309b6f24222246c18a8b65d3950e6e755440865.zip |
Merge tag 'docs/v5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
Pull rst conversion of docs from Mauro Carvalho Chehab:
"As agreed with Jon, I'm sending this big series directly to you, c/c
him, as this series required a special care, in order to avoid
conflicts with other trees"
* tag 'docs/v5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (77 commits)
docs: kbuild: fix build with pdf and fix some minor issues
docs: block: fix pdf output
docs: arm: fix a breakage with pdf output
docs: don't use nested tables
docs: gpio: add sysfs interface to the admin-guide
docs: locking: add it to the main index
docs: add some directories to the main documentation index
docs: add SPDX tags to new index files
docs: add a memory-devices subdir to driver-api
docs: phy: place documentation under driver-api
docs: serial: move it to the driver-api
docs: driver-api: add remaining converted dirs to it
docs: driver-api: add xilinx driver API documentation
docs: driver-api: add a series of orphaned documents
docs: admin-guide: add a series of orphaned documents
docs: cgroup-v1: add it to the admin-guide book
docs: aoe: add it to the driver-api book
docs: add some documentation dirs to the driver-api book
docs: driver-model: move it to the driver-api book
docs: lp855x-driver.rst: add it to the driver-api book
...
Diffstat (limited to 'Documentation/arm/samsung-s3c24xx/gpio.rst')
-rw-r--r-- | Documentation/arm/samsung-s3c24xx/gpio.rst | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/Documentation/arm/samsung-s3c24xx/gpio.rst b/Documentation/arm/samsung-s3c24xx/gpio.rst new file mode 100644 index 000000000000..f7c3d7d011a2 --- /dev/null +++ b/Documentation/arm/samsung-s3c24xx/gpio.rst @@ -0,0 +1,172 @@ +==================== +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.rst 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 while 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 |