Documentation / arm / Samsung-S3C24XX / GPIO.txt
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Based on kernel version 3.9. Page generated on 2013-05-02 22:54 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-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. 102 103 104 PIN Numbers 105 ----------- 106 107 Each pin has an unique number associated with it in regs-gpio.h, 108 e.g. 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. 115 116 117 Configuring a pin 118 ----------------- 119 120 The following function allows the configuration of a given pin to 121 be changed. 122 123 void s3c_gpio_cfgpin(unsigned int pin, unsigned int function); 124 125 e.g.: 126 127 s3c_gpio_cfgpin(S3C2410_GPA(0), S3C_GPIO_SFN(1)); 128 s3c_gpio_cfgpin(S3C2410_GPE(8), S3C_GPIO_SFN(2)); 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. 132 133 134 Reading the current configuration 135 --------------------------------- 136 137 The current configuration of a pin can be read by using standard 138 gpiolib function: 139 140 s3c_gpio_getcfg(unsigned int pin); 141 142 The return value will be from the same set of values which can be 143 passed to s3c_gpio_cfgpin(). 144 145 146 Configuring a pull-up resistor 147 ------------------------------ 148 149 A large proportion of the GPIO pins on the S3C2410 can have weak 150 pull-up resistors enabled. This can be configured by the following 151 function: 152 153 void s3c_gpio_setpull(unsigned int pin, unsigned int to); 154 155 Where the to value is S3C_GPIO_PULL_NONE to set the pull-up off, 156 and S3C_GPIO_PULL_UP to enable the specified pull-up. Any other 157 values are currently undefined. 158 159 160 Getting and setting the state of a PIN 161 -------------------------------------- 162 163 These calls are now implemented by the relevant gpiolib calls, convert 164 your board or driver to use gpiolib. 165 166 167 Getting the IRQ number associated with a PIN 168 -------------------------------------------- 169 170 A standard gpiolib function can map the given pin number to an IRQ 171 number to pass to the IRQ system. 172 173 int gpio_to_irq(unsigned int pin); 174 175 Note, not all pins have an IRQ. 176 177 178 Author 179 ------- 180 181 Ben Dooks, 03 October 2004 182 Copyright 2004 Ben Dooks, Simtec Electronics
- [ Samsung-S3C24XX ]
- CPUfreq.txt
- DMA.txt
- EB2410ITX.txt
- GPIO.txt
- H1940.txt
- NAND.txt
- Overview.txt
- S3C2412.txt
- S3C2413.txt
- SMDK2440.txt
- Suspend.txt
- USB-Host.txt
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