1 S3C2410 GPIO Control 2 ==================== 3 4Introduction 5------------ 6 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. 10 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. 14 15 See Documentation/arm/Samsung/GPIO.txt for the core implemetation. 16 17 18GPIOLIB 19------- 20 21 With the event of the GPIOLIB in drivers/gpio, support for some 22 of the GPIO functions such as reading and writing a pin will 23 be removed in favour of this common access method. 24 25 Once all the extant drivers have been converted, the functions 26 listed below will be removed (they may be marked as __deprecated 27 in the near future). 28 29 The following functions now either have a s3c_ specific variant 30 or are merged into gpiolib. See the definitions in 31 arch/arm/plat-samsung/include/plat/gpio-cfg.h: 32 33 s3c2410_gpio_setpin() gpio_set_value() or gpio_direction_output() 34 s3c2410_gpio_getpin() gpio_get_value() or gpio_direction_input() 35 s3c2410_gpio_getirq() gpio_to_irq() 36 s3c2410_gpio_cfgpin() s3c_gpio_cfgpin() 37 s3c2410_gpio_getcfg() s3c_gpio_getcfg() 38 s3c2410_gpio_pullup() s3c_gpio_setpull() 39 40 41GPIOLIB conversion 42------------------ 43 44If you need to convert your board or driver to use gpiolib from the exiting 45s3c2410 api, then here are some notes on the process. 46 471) If your board is exclusively using an GPIO, say to control peripheral 48 power, then it will require to claim the gpio with gpio_request() before 49 it can use it. 50 51 It is recommended to check the return value, with at least WARN_ON() 52 during initialisation. 53 542) The s3c2410_gpio_cfgpin() can be directly replaced with s3c_gpio_cfgpin() 55 as they have the same arguments, and can either take the pin specific 56 values, or the more generic special-function-number arguments. 57 583) s3c2410_gpio_pullup() changs have the problem that whilst the 59 s3c2410_gpio_pullup(x, 1) can be easily translated to the 60 s3c_gpio_setpull(x, S3C_GPIO_PULL_NONE), the s3c2410_gpio_pullup(x, 0) 61 are not so easy. 62 63 The s3c2410_gpio_pullup(x, 0) case enables the pull-up (or in the case 64 of some of the devices, a pull-down) and as such the new API distinguishes 65 between the UP and DOWN case. There is currently no 'just turn on' setting 66 which may be required if this becomes a problem. 67 684) s3c2410_gpio_setpin() can be replaced by gpio_set_value(), the old call 69 does not implicitly configure the relevant gpio to output. The gpio 70 direction should be changed before using gpio_set_value(). 71 725) s3c2410_gpio_getpin() is replaceable by gpio_get_value() if the pin 73 has been set to input. It is currently unknown what the behaviour is 74 when using gpio_get_value() on an output pin (s3c2410_gpio_getpin 75 would return the value the pin is supposed to be outputting). 76 776) s3c2410_gpio_getirq() should be directly replacable with the 78 gpio_to_irq() call. 79 80The s3c2410_gpio and gpio_ calls have always operated on the same gpio 81numberspace, so there is no problem with converting the gpio numbering 82between the calls. 83 84 85Headers 86------- 87 88 See arch/arm/mach-s3c2410/include/mach/regs-gpio.h for the list 89 of GPIO pins, and the configuration values for them. This 90 is included by using #include <mach/regs-gpio.h> 91 92 The GPIO management functions are defined in the hardware 93 header arch/arm/mach-s3c2410/include/mach/hardware.h which can be 94 included by #include <mach/hardware.h> 95 96 A useful amount of documentation can be found in the hardware 97 header on how the GPIO functions (and others) work. 98 99 Whilst a number of these functions do make some checks on what 100 is passed to them, for speed of use, they may not always ensure 101 that the user supplied data to them is correct. 102 103 104PIN Numbers 105----------- 106 107 Each pin has an unique number associated with it in regs-gpio.h, 108 eg S3C2410_GPA(0) or S3C2410_GPF(1). These defines are used to tell 109 the GPIO functions which pin is to be used. 110 111 With the conversion to gpiolib, there is no longer a direct conversion 112 from gpio pin number to register base address as in earlier kernels. This 113 is due to the number space required for newer SoCs where the later 114 GPIOs are not contiguous. 115 116 117Configuring a pin 118----------------- 119 120 The following function allows the configuration of a given pin to 121 be changed. 122 123 void s3c2410_gpio_cfgpin(unsigned int pin, unsigned int function); 124 125 Eg: 126 127 s3c2410_gpio_cfgpin(S3C2410_GPA(0), S3C2410_GPA0_ADDR0); 128 s3c2410_gpio_cfgpin(S3C2410_GPE(8), S3C2410_GPE8_SDDAT1); 129 130 which would turn GPA(0) into the lowest Address line A0, and set 131 GPE(8) to be connected to the SDIO/MMC controller's SDDAT1 line. 132 133 The s3c_gpio_cfgpin() call is a functional replacement for this call. 134 135 136Reading the current configuration 137--------------------------------- 138 139 The current configuration of a pin can be read by using: 140 141 s3c2410_gpio_getcfg(unsigned int pin); 142 143 The return value will be from the same set of values which can be 144 passed to s3c2410_gpio_cfgpin(). 145 146 The s3c_gpio_getcfg() call should be a functional replacement for 147 this call. 148 149 150Configuring a pull-up resistor 151------------------------------ 152 153 A large proportion of the GPIO pins on the S3C2410 can have weak 154 pull-up resistors enabled. This can be configured by the following 155 function: 156 157 void s3c2410_gpio_pullup(unsigned int pin, unsigned int to); 158 159 Where the to value is zero to set the pull-up off, and 1 to enable 160 the specified pull-up. Any other values are currently undefined. 161 162 The s3c_gpio_setpull() offers similar functionality, but with the 163 ability to encode whether the pull is up or down. Currently there 164 is no 'just on' state, so up or down must be selected. 165 166 167Getting the state of a PIN 168-------------------------- 169 170 The state of a pin can be read by using the function: 171 172 unsigned int s3c2410_gpio_getpin(unsigned int pin); 173 174 This will return either zero or non-zero. Do not count on this 175 function returning 1 if the pin is set. 176 177 This call is now implemented by the relevant gpiolib calls, convert 178 your board or driver to use gpiolib. 179 180 181Setting the state of a PIN 182-------------------------- 183 184 The value an pin is outputing can be modified by using the following: 185 186 void s3c2410_gpio_setpin(unsigned int pin, unsigned int to); 187 188 Which sets the given pin to the value. Use 0 to write 0, and 1 to 189 set the output to 1. 190 191 This call is now implemented by the relevant gpiolib calls, convert 192 your board or driver to use gpiolib. 193 194 195Getting the IRQ number associated with a PIN 196-------------------------------------------- 197 198 The following function can map the given pin number to an IRQ 199 number to pass to the IRQ system. 200 201 int s3c2410_gpio_getirq(unsigned int pin); 202 203 Note, not all pins have an IRQ. 204 205 This call is now implemented by the relevant gpiolib calls, convert 206 your board or driver to use gpiolib. 207 208 209Authour 210------- 211 212 213Ben Dooks, 03 October 2004 214Copyright 2004 Ben Dooks, Simtec Electronics 215