Based on kernel version 4.16.1. Page generated on 2018-04-09 11:52 EST.
1 S3C24XX GPIO Control 2 ==================== 3 4 Introduction 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 implementation. 16 17 18 GPIOLIB 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 41 GPIOLIB conversion 42 ------------------ 43 44 If you need to convert your board or driver to use gpiolib from the phased 45 out s3c2410 API, then here are some notes on the process. 46 47 1) 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 54 2) 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 58 3) s3c2410_gpio_pullup() changes 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 68 4) 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 72 5) 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 77 6) s3c2410_gpio_getirq() should be directly replaceable with the 78 gpio_to_irq() call. 79 80 The s3c2410_gpio and gpio_ calls have always operated on the same gpio 81 numberspace, so there is no problem with converting the gpio numbering 82 between the calls. 83 84 85 Headers 86 ------- 87 88 See arch/arm/mach-s3c24xx/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 93 PIN Numbers 94 ----------- 95 96 Each pin has an unique number associated with it in regs-gpio.h, 97 e.g. S3C2410_GPA(0) or S3C2410_GPF(1). These defines are used to tell 98 the GPIO functions which pin is to be used. 99 100 With the conversion to gpiolib, there is no longer a direct conversion 101 from gpio pin number to register base address as in earlier kernels. This 102 is due to the number space required for newer SoCs where the later 103 GPIOs are not contiguous. 104 105 106 Configuring a pin 107 ----------------- 108 109 The following function allows the configuration of a given pin to 110 be changed. 111 112 void s3c_gpio_cfgpin(unsigned int pin, unsigned int function); 113 114 e.g.: 115 116 s3c_gpio_cfgpin(S3C2410_GPA(0), S3C_GPIO_SFN(1)); 117 s3c_gpio_cfgpin(S3C2410_GPE(8), S3C_GPIO_SFN(2)); 118 119 which would turn GPA(0) into the lowest Address line A0, and set 120 GPE(8) to be connected to the SDIO/MMC controller's SDDAT1 line. 121 122 123 Reading the current configuration 124 --------------------------------- 125 126 The current configuration of a pin can be read by using standard 127 gpiolib function: 128 129 s3c_gpio_getcfg(unsigned int pin); 130 131 The return value will be from the same set of values which can be 132 passed to s3c_gpio_cfgpin(). 133 134 135 Configuring a pull-up resistor 136 ------------------------------ 137 138 A large proportion of the GPIO pins on the S3C2410 can have weak 139 pull-up resistors enabled. This can be configured by the following 140 function: 141 142 void s3c_gpio_setpull(unsigned int pin, unsigned int to); 143 144 Where the to value is S3C_GPIO_PULL_NONE to set the pull-up off, 145 and S3C_GPIO_PULL_UP to enable the specified pull-up. Any other 146 values are currently undefined. 147 148 149 Getting and setting the state of a PIN 150 -------------------------------------- 151 152 These calls are now implemented by the relevant gpiolib calls, convert 153 your board or driver to use gpiolib. 154 155 156 Getting the IRQ number associated with a PIN 157 -------------------------------------------- 158 159 A standard gpiolib function can map the given pin number to an IRQ 160 number to pass to the IRQ system. 161 162 int gpio_to_irq(unsigned int pin); 163 164 Note, not all pins have an IRQ. 165 166 167 Author 168 ------- 169 170 Ben Dooks, 03 October 2004 171 Copyright 2004 Ben Dooks, Simtec Electronics