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1 | S3C2410 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 | ||
d192baea BD |
15 | See Documentation/arm/Samsung/GPIO.txt for the core implemetation. |
16 | ||
1da177e4 | 17 | |
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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 | ||
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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() | |
f47c32f3 BD |
39 | |
40 | ||
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41 | GPIOLIB conversion |
42 | ------------------ | |
43 | ||
44 | If you need to convert your board or driver to use gpiolib from the exiting | |
45 | 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() 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 | ||
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 replacable 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 | ||
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85 | Headers |
86 | ------- | |
87 | ||
a09e64fb | 88 | See arch/arm/mach-s3c2410/include/mach/regs-gpio.h for the list |
1da177e4 | 89 | of GPIO pins, and the configuration values for them. This |
a09e64fb | 90 | is included by using #include <mach/regs-gpio.h> |
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91 | |
92 | The GPIO management functions are defined in the hardware | |
a09e64fb RK |
93 | header arch/arm/mach-s3c2410/include/mach/hardware.h which can be |
94 | included by #include <mach/hardware.h> | |
1da177e4 | 95 | |
3f6dee9b | 96 | A useful amount of documentation can be found in the hardware |
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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, | |
070276d5 | 108 | eg S3C2410_GPA(0) or S3C2410_GPF(1). These defines are used to tell |
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109 | the GPIO functions which pin is to be used. |
110 | ||
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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 | ||
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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 s3c2410_gpio_cfgpin(unsigned int pin, unsigned int function); | |
124 | ||
125 | Eg: | |
126 | ||
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127 | s3c2410_gpio_cfgpin(S3C2410_GPA(0), S3C2410_GPA0_ADDR0); |
128 | s3c2410_gpio_cfgpin(S3C2410_GPE(8), S3C2410_GPE8_SDDAT1); | |
1da177e4 | 129 | |
070276d5 BD |
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. | |
1da177e4 | 132 | |
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133 | The s3c_gpio_cfgpin() call is a functional replacement for this call. |
134 | ||
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135 | |
136 | Reading 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 | ||
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146 | The s3c_gpio_getcfg() call should be a functional replacement for |
147 | this call. | |
148 | ||
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149 | |
150 | Configuring 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 | ||
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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 | ||
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166 | |
167 | Getting 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 | ||
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177 | This call is now implemented by the relevant gpiolib calls, convert |
178 | your board or driver to use gpiolib. | |
179 | ||
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180 | |
181 | Setting 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 | ||
70f5c9a4 BD |
191 | This call is now implemented by the relevant gpiolib calls, convert |
192 | your board or driver to use gpiolib. | |
193 | ||
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194 | |
195 | Getting 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 | ||
70f5c9a4 BD |
205 | This call is now implemented by the relevant gpiolib calls, convert |
206 | your board or driver to use gpiolib. | |
207 | ||
1da177e4 LT |
208 | |
209 | Authour | |
210 | ------- | |
211 | ||
212 | ||
213 | Ben Dooks, 03 October 2004 | |
50f430e3 | 214 | Copyright 2004 Ben Dooks, Simtec Electronics |