gpio.rst (5607B)
1==================== 2S3C24XX GPIO Control 3==================== 4 5Introduction 6------------ 7 8 The s3c2410 kernel provides an interface to configure and 9 manipulate the state of the GPIO pins, and find out other 10 information about them. 11 12 There are a number of conditions attached to the configuration 13 of the s3c2410 GPIO system, please read the Samsung provided 14 data-sheet/users manual to find out the complete list. 15 16 See Documentation/arm/samsung/gpio.rst for the core implementation. 17 18 19GPIOLIB 20------- 21 22 With the event of the GPIOLIB in drivers/gpio, support for some 23 of the GPIO functions such as reading and writing a pin will 24 be removed in favour of this common access method. 25 26 Once all the extant drivers have been converted, the functions 27 listed below will be removed (they may be marked as __deprecated 28 in the near future). 29 30 The following functions now either have a `s3c_` specific variant 31 or are merged into gpiolib. See the definitions in 32 arch/arm/mach-s3c/gpio-cfg.h: 33 34 - s3c2410_gpio_setpin() gpio_set_value() or gpio_direction_output() 35 - s3c2410_gpio_getpin() gpio_get_value() or gpio_direction_input() 36 - s3c2410_gpio_getirq() gpio_to_irq() 37 - s3c2410_gpio_cfgpin() s3c_gpio_cfgpin() 38 - s3c2410_gpio_getcfg() s3c_gpio_getcfg() 39 - s3c2410_gpio_pullup() s3c_gpio_setpull() 40 41 42GPIOLIB conversion 43------------------ 44 45If you need to convert your board or driver to use gpiolib from the phased 46out s3c2410 API, then here are some notes on the process. 47 481) If your board is exclusively using an GPIO, say to control peripheral 49 power, then it will require to claim the gpio with gpio_request() before 50 it can use it. 51 52 It is recommended to check the return value, with at least WARN_ON() 53 during initialisation. 54 552) The s3c2410_gpio_cfgpin() can be directly replaced with s3c_gpio_cfgpin() 56 as they have the same arguments, and can either take the pin specific 57 values, or the more generic special-function-number arguments. 58 593) s3c2410_gpio_pullup() changes have the problem that while the 60 s3c2410_gpio_pullup(x, 1) can be easily translated to the 61 s3c_gpio_setpull(x, S3C_GPIO_PULL_NONE), the s3c2410_gpio_pullup(x, 0) 62 are not so easy. 63 64 The s3c2410_gpio_pullup(x, 0) case enables the pull-up (or in the case 65 of some of the devices, a pull-down) and as such the new API distinguishes 66 between the UP and DOWN case. There is currently no 'just turn on' setting 67 which may be required if this becomes a problem. 68 694) s3c2410_gpio_setpin() can be replaced by gpio_set_value(), the old call 70 does not implicitly configure the relevant gpio to output. The gpio 71 direction should be changed before using gpio_set_value(). 72 735) s3c2410_gpio_getpin() is replaceable by gpio_get_value() if the pin 74 has been set to input. It is currently unknown what the behaviour is 75 when using gpio_get_value() on an output pin (s3c2410_gpio_getpin 76 would return the value the pin is supposed to be outputting). 77 786) s3c2410_gpio_getirq() should be directly replaceable with the 79 gpio_to_irq() call. 80 81The s3c2410_gpio and `gpio_` calls have always operated on the same gpio 82numberspace, so there is no problem with converting the gpio numbering 83between the calls. 84 85 86Headers 87------- 88 89 See arch/arm/mach-s3c/regs-gpio-s3c24xx.h for the list 90 of GPIO pins, and the configuration values for them. This 91 is included by using #include <mach/regs-gpio.h> 92 93 94PIN Numbers 95----------- 96 97 Each pin has an unique number associated with it in regs-gpio.h, 98 e.g. S3C2410_GPA(0) or S3C2410_GPF(1). These defines are used to tell 99 the GPIO functions which pin is to be used. 100 101 With the conversion to gpiolib, there is no longer a direct conversion 102 from gpio pin number to register base address as in earlier kernels. This 103 is due to the number space required for newer SoCs where the later 104 GPIOs are not contiguous. 105 106 107Configuring a pin 108----------------- 109 110 The following function allows the configuration of a given pin to 111 be changed. 112 113 void s3c_gpio_cfgpin(unsigned int pin, unsigned int function); 114 115 e.g.: 116 117 s3c_gpio_cfgpin(S3C2410_GPA(0), S3C_GPIO_SFN(1)); 118 s3c_gpio_cfgpin(S3C2410_GPE(8), S3C_GPIO_SFN(2)); 119 120 which would turn GPA(0) into the lowest Address line A0, and set 121 GPE(8) to be connected to the SDIO/MMC controller's SDDAT1 line. 122 123 124Reading the current configuration 125--------------------------------- 126 127 The current configuration of a pin can be read by using standard 128 gpiolib function: 129 130 s3c_gpio_getcfg(unsigned int pin); 131 132 The return value will be from the same set of values which can be 133 passed to s3c_gpio_cfgpin(). 134 135 136Configuring a pull-up resistor 137------------------------------ 138 139 A large proportion of the GPIO pins on the S3C2410 can have weak 140 pull-up resistors enabled. This can be configured by the following 141 function: 142 143 void s3c_gpio_setpull(unsigned int pin, unsigned int to); 144 145 Where the to value is S3C_GPIO_PULL_NONE to set the pull-up off, 146 and S3C_GPIO_PULL_UP to enable the specified pull-up. Any other 147 values are currently undefined. 148 149 150Getting and setting the state of a PIN 151-------------------------------------- 152 153 These calls are now implemented by the relevant gpiolib calls, convert 154 your board or driver to use gpiolib. 155 156 157Getting the IRQ number associated with a PIN 158-------------------------------------------- 159 160 A standard gpiolib function can map the given pin number to an IRQ 161 number to pass to the IRQ system. 162 163 int gpio_to_irq(unsigned int pin); 164 165 Note, not all pins have an IRQ. 166 167 168Author 169------- 170 171Ben Dooks, 03 October 2004 172Copyright 2004 Ben Dooks, Simtec Electronics