1 /**
2 * drivers/gpio/max7301.c
3 *
4 * Copyright (C) 2006 Juergen Beisert, Pengutronix
5 * Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * The Maxim's MAX7301 device is an SPI driven GPIO expander. There are
12 * 28 GPIOs. 8 of them can trigger an interrupt. See datasheet for more
13 * details
14 * Note:
15 * - DIN must be stable at the rising edge of clock.
16 * - when writing:
17 * - always clock in 16 clocks at once
18 * - at DIN: D15 first, D0 last
19 * - D0..D7 = databyte, D8..D14 = commandbyte
20 * - D15 = low -> write command
21 * - when reading
22 * - always clock in 16 clocks at once
23 * - at DIN: D15 first, D0 last
24 * - D0..D7 = dummy, D8..D14 = register address
25 * - D15 = high -> read command
26 * - raise CS and assert it again
27 * - always clock in 16 clocks at once
28 * - at DOUT: D15 first, D0 last
29 * - D0..D7 contains the data from the first cycle
30 *
31 * The driver exports a standard gpiochip interface
32 */
33
34 #include <linux/init.h>
35 #include <linux/platform_device.h>
36 #include <linux/mutex.h>
37 #include <linux/spi/spi.h>
38 #include <linux/spi/max7301.h>
39 #include <linux/gpio.h>
40
41 #define DRIVER_NAME "max7301"
42
43 /*
44 * Pin configurations, see MAX7301 datasheet page 6
45 */
46 #define PIN_CONFIG_MASK 0x03
47 #define PIN_CONFIG_IN_PULLUP 0x03
48 #define PIN_CONFIG_IN_WO_PULLUP 0x02
49 #define PIN_CONFIG_OUT 0x01
50
51 #define PIN_NUMBER 28
52
53
54 /*
55 * Some registers must be read back to modify.
56 * To save time we cache them here in memory
57 */
58 struct max7301 {
59 struct mutex lock;
60 u8 port_config[8]; /* field 0 is unused */
61 u32 out_level; /* cached output levels */
62 struct gpio_chip chip;
63 struct spi_device *spi;
64 };
65
66 /**
67 * max7301_write - Write a new register content
68 * @spi: The SPI device
69 * @reg: Register offset
70 * @val: Value to write
71 *
72 * A write to the MAX7301 means one message with one transfer
73 *
74 * Returns 0 if successful or a negative value on error
75 */
max7301_write(struct spi_device * spi,unsigned int reg,unsigned int val)76 static int max7301_write(struct spi_device *spi, unsigned int reg, unsigned int val)
77 {
78 u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);
79 return spi_write(spi, (const u8 *)&word, sizeof(word));
80 }
81
82 /**
83 * max7301_read - Read back register content
84 * @spi: The SPI device
85 * @reg: Register offset
86 *
87 * A read from the MAX7301 means two transfers; here, one message each
88 *
89 * Returns positive 8 bit value from device if successful or a
90 * negative value on error
91 */
max7301_read(struct spi_device * spi,unsigned int reg)92 static int max7301_read(struct spi_device *spi, unsigned int reg)
93 {
94 int ret;
95 u16 word;
96
97 word = 0x8000 | (reg << 8);
98 ret = spi_write(spi, (const u8 *)&word, sizeof(word));
99 if (ret)
100 return ret;
101 /*
102 * This relies on the fact, that a transfer with NULL tx_buf shifts out
103 * zero bytes (=NOOP for MAX7301)
104 */
105 ret = spi_read(spi, (u8 *)&word, sizeof(word));
106 if (ret)
107 return ret;
108 return word & 0xff;
109 }
110
max7301_direction_input(struct gpio_chip * chip,unsigned offset)111 static int max7301_direction_input(struct gpio_chip *chip, unsigned offset)
112 {
113 struct max7301 *ts = container_of(chip, struct max7301, chip);
114 u8 *config;
115 int ret;
116
117 /* First 4 pins are unused in the controller */
118 offset += 4;
119
120 config = &ts->port_config[offset >> 2];
121
122 mutex_lock(&ts->lock);
123
124 /* Standard GPIO API doesn't support pull-ups, has to be extended.
125 * Hard-coding no pollup for now. */
126 *config = (*config & ~(3 << (offset & 3))) | (1 << (offset & 3));
127
128 ret = max7301_write(ts->spi, 0x08 + (offset >> 2), *config);
129
130 mutex_unlock(&ts->lock);
131
132 return ret;
133 }
134
__max7301_set(struct max7301 * ts,unsigned offset,int value)135 static int __max7301_set(struct max7301 *ts, unsigned offset, int value)
136 {
137 if (value) {
138 ts->out_level |= 1 << offset;
139 return max7301_write(ts->spi, 0x20 + offset, 0x01);
140 } else {
141 ts->out_level &= ~(1 << offset);
142 return max7301_write(ts->spi, 0x20 + offset, 0x00);
143 }
144 }
145
max7301_direction_output(struct gpio_chip * chip,unsigned offset,int value)146 static int max7301_direction_output(struct gpio_chip *chip, unsigned offset,
147 int value)
148 {
149 struct max7301 *ts = container_of(chip, struct max7301, chip);
150 u8 *config;
151 int ret;
152
153 /* First 4 pins are unused in the controller */
154 offset += 4;
155
156 config = &ts->port_config[offset >> 2];
157
158 mutex_lock(&ts->lock);
159
160 *config = (*config & ~(3 << (offset & 3))) | (1 << (offset & 3));
161
162 ret = __max7301_set(ts, offset, value);
163
164 if (!ret)
165 ret = max7301_write(ts->spi, 0x08 + (offset >> 2), *config);
166
167 mutex_unlock(&ts->lock);
168
169 return ret;
170 }
171
max7301_get(struct gpio_chip * chip,unsigned offset)172 static int max7301_get(struct gpio_chip *chip, unsigned offset)
173 {
174 struct max7301 *ts = container_of(chip, struct max7301, chip);
175 int config, level = -EINVAL;
176
177 /* First 4 pins are unused in the controller */
178 offset += 4;
179
180 mutex_lock(&ts->lock);
181
182 config = (ts->port_config[offset >> 2] >> ((offset & 3) * 2)) & 3;
183
184 switch (config) {
185 case 1:
186 /* Output: return cached level */
187 level = !!(ts->out_level & (1 << offset));
188 break;
189 case 2:
190 case 3:
191 /* Input: read out */
192 level = max7301_read(ts->spi, 0x20 + offset) & 0x01;
193 }
194 mutex_unlock(&ts->lock);
195
196 return level;
197 }
198
max7301_set(struct gpio_chip * chip,unsigned offset,int value)199 static void max7301_set(struct gpio_chip *chip, unsigned offset, int value)
200 {
201 struct max7301 *ts = container_of(chip, struct max7301, chip);
202
203 /* First 4 pins are unused in the controller */
204 offset += 4;
205
206 mutex_lock(&ts->lock);
207
208 __max7301_set(ts, offset, value);
209
210 mutex_unlock(&ts->lock);
211 }
212
max7301_probe(struct spi_device * spi)213 static int __devinit max7301_probe(struct spi_device *spi)
214 {
215 struct max7301 *ts;
216 struct max7301_platform_data *pdata;
217 int i, ret;
218
219 pdata = spi->dev.platform_data;
220 if (!pdata || !pdata->base) {
221 dev_dbg(&spi->dev, "incorrect or missing platform data\n");
222 return -EINVAL;
223 }
224
225 /*
226 * bits_per_word cannot be configured in platform data
227 */
228 spi->bits_per_word = 16;
229
230 ret = spi_setup(spi);
231 if (ret < 0)
232 return ret;
233
234 ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
235 if (!ts)
236 return -ENOMEM;
237
238 mutex_init(&ts->lock);
239
240 dev_set_drvdata(&spi->dev, ts);
241
242 /* Power up the chip and disable IRQ output */
243 max7301_write(spi, 0x04, 0x01);
244
245 ts->spi = spi;
246
247 ts->chip.label = DRIVER_NAME,
248
249 ts->chip.direction_input = max7301_direction_input;
250 ts->chip.get = max7301_get;
251 ts->chip.direction_output = max7301_direction_output;
252 ts->chip.set = max7301_set;
253
254 ts->chip.base = pdata->base;
255 ts->chip.ngpio = PIN_NUMBER;
256 ts->chip.can_sleep = 1;
257 ts->chip.dev = &spi->dev;
258 ts->chip.owner = THIS_MODULE;
259
260 /*
261 * tristate all pins in hardware and cache the
262 * register values for later use.
263 */
264 for (i = 1; i < 8; i++) {
265 int j;
266 /* 0xAA means input with internal pullup disabled */
267 max7301_write(spi, 0x08 + i, 0xAA);
268 ts->port_config[i] = 0xAA;
269 for (j = 0; j < 4; j++) {
270 int offset = (i - 1) * 4 + j;
271 ret = max7301_direction_input(&ts->chip, offset);
272 if (ret)
273 goto exit_destroy;
274 }
275 }
276
277 ret = gpiochip_add(&ts->chip);
278 if (ret)
279 goto exit_destroy;
280
281 return ret;
282
283 exit_destroy:
284 dev_set_drvdata(&spi->dev, NULL);
285 mutex_destroy(&ts->lock);
286 kfree(ts);
287 return ret;
288 }
289
max7301_remove(struct spi_device * spi)290 static int max7301_remove(struct spi_device *spi)
291 {
292 struct max7301 *ts;
293 int ret;
294
295 ts = dev_get_drvdata(&spi->dev);
296 if (ts == NULL)
297 return -ENODEV;
298
299 dev_set_drvdata(&spi->dev, NULL);
300
301 /* Power down the chip and disable IRQ output */
302 max7301_write(spi, 0x04, 0x00);
303
304 ret = gpiochip_remove(&ts->chip);
305 if (!ret) {
306 mutex_destroy(&ts->lock);
307 kfree(ts);
308 } else
309 dev_err(&spi->dev, "Failed to remove the GPIO controller: %d\n",
310 ret);
311
312 return ret;
313 }
314
315 static struct spi_driver max7301_driver = {
316 .driver = {
317 .name = DRIVER_NAME,
318 .owner = THIS_MODULE,
319 },
320 .probe = max7301_probe,
321 .remove = __devexit_p(max7301_remove),
322 };
323
max7301_init(void)324 static int __init max7301_init(void)
325 {
326 return spi_register_driver(&max7301_driver);
327 }
328 /* register after spi postcore initcall and before
329 * subsys initcalls that may rely on these GPIOs
330 */
331 subsys_initcall(max7301_init);
332
max7301_exit(void)333 static void __exit max7301_exit(void)
334 {
335 spi_unregister_driver(&max7301_driver);
336 }
337 module_exit(max7301_exit);
338
339 MODULE_AUTHOR("Juergen Beisert");
340 MODULE_LICENSE("GPL v2");
341 MODULE_DESCRIPTION("MAX7301 SPI based GPIO-Expander");
342