7 The s3c2410 kernel provides an interface to configure and
8 manipulate the state of the GPIO pins, and find out other
9 information about them.
11 There are a number of conditions attached to the configuration
12 of the s3c2410 GPIO system, please read the Samsung provided
13 data-sheet/users manual to find out the complete list.
19 With the event of the GPIOLIB in drivers/gpio, support for some
20 of the GPIO functions such as reading and writing a pin will
21 be removed in favour of this common access method.
23 Once all the extant drivers have been converted, the functions
24 listed below will be removed (they may be marked as __deprecated
27 The following functions now either have a s3c_ specific variant
28 or are merged into gpiolib. See the definitions in
29 arch/arm/plat-samsung/include/plat/gpio-cfg.h:
31 s3c2410_gpio_setpin() gpio_set_value() or gpio_direction_output()
32 s3c2410_gpio_getpin() gpio_get_value() or gpio_direction_input()
33 s3c2410_gpio_getirq() gpio_to_irq()
34 s3c2410_gpio_cfgpin() s3c_gpio_cfgpin()
35 s3c2410_gpio_getcfg() s3c_gpio_getcfg()
36 s3c2410_gpio_pullup() s3c_gpio_setpull()
42 If you need to convert your board or driver to use gpiolib from the exiting
43 s3c2410 api, then here are some notes on the process.
45 1) If your board is exclusively using an GPIO, say to control peripheral
46 power, then it will require to claim the gpio with gpio_request() before
49 It is recommended to check the return value, with at least WARN_ON()
50 during initialisation.
52 2) The s3c2410_gpio_cfgpin() can be directly replaced with s3c_gpio_cfgpin()
53 as they have the same arguments, and can either take the pin specific
54 values, or the more generic special-function-number arguments.
56 3) s3c2410_gpio_pullup() changs have the problem that whilst the
57 s3c2410_gpio_pullup(x, 1) can be easily translated to the
58 s3c_gpio_setpull(x, S3C_GPIO_PULL_NONE), the s3c2410_gpio_pullup(x, 0)
61 The s3c2410_gpio_pullup(x, 0) case enables the pull-up (or in the case
62 of some of the devices, a pull-down) and as such the new API distinguishes
63 between the UP and DOWN case. There is currently no 'just turn on' setting
64 which may be required if this becomes a problem.
66 4) s3c2410_gpio_setpin() can be replaced by gpio_set_value(), the old call
67 does not implicitly configure the relevant gpio to output. The gpio
68 direction should be changed before using gpio_set_value().
70 5) s3c2410_gpio_getpin() is replaceable by gpio_get_value() if the pin
71 has been set to input. It is currently unknown what the behaviour is
72 when using gpio_get_value() on an output pin (s3c2410_gpio_getpin
73 would return the value the pin is supposed to be outputting).
75 6) s3c2410_gpio_getirq() should be directly replacable with the
78 The s3c2410_gpio and gpio_ calls have always operated on the same gpio
79 numberspace, so there is no problem with converting the gpio numbering
86 See arch/arm/mach-s3c2410/include/mach/regs-gpio.h for the list
87 of GPIO pins, and the configuration values for them. This
88 is included by using #include <mach/regs-gpio.h>
90 The GPIO management functions are defined in the hardware
91 header arch/arm/mach-s3c2410/include/mach/hardware.h which can be
92 included by #include <mach/hardware.h>
94 A useful amount of documentation can be found in the hardware
95 header on how the GPIO functions (and others) work.
97 Whilst a number of these functions do make some checks on what
98 is passed to them, for speed of use, they may not always ensure
99 that the user supplied data to them is correct.
105 Each pin has an unique number associated with it in regs-gpio.h,
106 eg S3C2410_GPA(0) or S3C2410_GPF(1). These defines are used to tell
107 the GPIO functions which pin is to be used.
109 With the conversion to gpiolib, there is no longer a direct conversion
110 from gpio pin number to register base address as in earlier kernels. This
111 is due to the number space required for newer SoCs where the later
112 GPIOs are not contiguous.
118 The following function allows the configuration of a given pin to
121 void s3c2410_gpio_cfgpin(unsigned int pin, unsigned int function);
125 s3c2410_gpio_cfgpin(S3C2410_GPA(0), S3C2410_GPA0_ADDR0);
126 s3c2410_gpio_cfgpin(S3C2410_GPE(8), S3C2410_GPE8_SDDAT1);
128 which would turn GPA(0) into the lowest Address line A0, and set
129 GPE(8) to be connected to the SDIO/MMC controller's SDDAT1 line.
131 The s3c_gpio_cfgpin() call is a functional replacement for this call.
134 Reading the current configuration
135 ---------------------------------
137 The current configuration of a pin can be read by using:
139 s3c2410_gpio_getcfg(unsigned int pin);
141 The return value will be from the same set of values which can be
142 passed to s3c2410_gpio_cfgpin().
144 The s3c_gpio_getcfg() call should be a functional replacement for
148 Configuring a pull-up resistor
149 ------------------------------
151 A large proportion of the GPIO pins on the S3C2410 can have weak
152 pull-up resistors enabled. This can be configured by the following
155 void s3c2410_gpio_pullup(unsigned int pin, unsigned int to);
157 Where the to value is zero to set the pull-up off, and 1 to enable
158 the specified pull-up. Any other values are currently undefined.
160 The s3c_gpio_setpull() offers similar functionality, but with the
161 ability to encode whether the pull is up or down. Currently there
162 is no 'just on' state, so up or down must be selected.
165 Getting the state of a PIN
166 --------------------------
168 The state of a pin can be read by using the function:
170 unsigned int s3c2410_gpio_getpin(unsigned int pin);
172 This will return either zero or non-zero. Do not count on this
173 function returning 1 if the pin is set.
175 This call is now implemented by the relevant gpiolib calls, convert
176 your board or driver to use gpiolib.
179 Setting the state of a PIN
180 --------------------------
182 The value an pin is outputing can be modified by using the following:
184 void s3c2410_gpio_setpin(unsigned int pin, unsigned int to);
186 Which sets the given pin to the value. Use 0 to write 0, and 1 to
189 This call is now implemented by the relevant gpiolib calls, convert
190 your board or driver to use gpiolib.
193 Getting the IRQ number associated with a PIN
194 --------------------------------------------
196 The following function can map the given pin number to an IRQ
197 number to pass to the IRQ system.
199 int s3c2410_gpio_getirq(unsigned int pin);
201 Note, not all pins have an IRQ.
203 This call is now implemented by the relevant gpiolib calls, convert
204 your board or driver to use gpiolib.
211 Ben Dooks, 03 October 2004
212 Copyright 2004 Ben Dooks, Simtec Electronics