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Juergen Beisert0c36ec32008-07-21 14:21:34 -07001/**
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 */
58struct 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 */
76static 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 */
92static 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
111static 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
135static 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
146static 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
172static 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
199static 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
213static 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 return -ENODEV;
222
223 /*
224 * bits_per_word cannot be configured in platform data
225 */
226 spi->bits_per_word = 16;
227
228 ret = spi_setup(spi);
229 if (ret < 0)
230 return ret;
231
232 ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
233 if (!ts)
234 return -ENOMEM;
235
236 mutex_init(&ts->lock);
237
238 dev_set_drvdata(&spi->dev, ts);
239
240 /* Power up the chip and disable IRQ output */
241 max7301_write(spi, 0x04, 0x01);
242
243 ts->spi = spi;
244
245 ts->chip.label = DRIVER_NAME,
246
247 ts->chip.direction_input = max7301_direction_input;
248 ts->chip.get = max7301_get;
249 ts->chip.direction_output = max7301_direction_output;
250 ts->chip.set = max7301_set;
251
252 ts->chip.base = pdata->base;
253 ts->chip.ngpio = PIN_NUMBER;
254 ts->chip.can_sleep = 1;
255 ts->chip.dev = &spi->dev;
256 ts->chip.owner = THIS_MODULE;
257
Juergen Beisert0c36ec32008-07-21 14:21:34 -0700258 /*
259 * tristate all pins in hardware and cache the
260 * register values for later use.
261 */
262 for (i = 1; i < 8; i++) {
263 int j;
264 /* 0xAA means input with internal pullup disabled */
265 max7301_write(spi, 0x08 + i, 0xAA);
266 ts->port_config[i] = 0xAA;
267 for (j = 0; j < 4; j++) {
Dmitry Baryshkovc557fa32008-10-15 22:03:11 -0700268 int offset = (i - 1) * 4 + j;
269 ret = max7301_direction_input(&ts->chip, offset);
Juergen Beisert0c36ec32008-07-21 14:21:34 -0700270 if (ret)
Dmitry Baryshkovc557fa32008-10-15 22:03:11 -0700271 goto exit_destroy;
Juergen Beisert0c36ec32008-07-21 14:21:34 -0700272 }
273 }
Dmitry Baryshkovc557fa32008-10-15 22:03:11 -0700274
275 ret = gpiochip_add(&ts->chip);
276 if (ret)
277 goto exit_destroy;
278
Juergen Beisert0c36ec32008-07-21 14:21:34 -0700279 return ret;
280
Juergen Beisert0c36ec32008-07-21 14:21:34 -0700281exit_destroy:
282 dev_set_drvdata(&spi->dev, NULL);
283 mutex_destroy(&ts->lock);
284 kfree(ts);
285 return ret;
286}
287
288static int max7301_remove(struct spi_device *spi)
289{
290 struct max7301 *ts;
291 int ret;
292
293 ts = dev_get_drvdata(&spi->dev);
294 if (ts == NULL)
295 return -ENODEV;
296
297 dev_set_drvdata(&spi->dev, NULL);
298
299 /* Power down the chip and disable IRQ output */
300 max7301_write(spi, 0x04, 0x00);
301
302 ret = gpiochip_remove(&ts->chip);
303 if (!ret) {
304 mutex_destroy(&ts->lock);
305 kfree(ts);
306 } else
307 dev_err(&spi->dev, "Failed to remove the GPIO controller: %d\n",
308 ret);
309
310 return ret;
311}
312
313static struct spi_driver max7301_driver = {
314 .driver = {
315 .name = DRIVER_NAME,
316 .owner = THIS_MODULE,
317 },
318 .probe = max7301_probe,
319 .remove = __devexit_p(max7301_remove),
320};
321
322static int __init max7301_init(void)
323{
324 return spi_register_driver(&max7301_driver);
325}
David Brownell673c0c02008-10-15 22:02:46 -0700326/* register after spi postcore initcall and before
327 * subsys initcalls that may rely on these GPIOs
328 */
329subsys_initcall(max7301_init);
Juergen Beisert0c36ec32008-07-21 14:21:34 -0700330
331static void __exit max7301_exit(void)
332{
333 spi_unregister_driver(&max7301_driver);
334}
Juergen Beisert0c36ec32008-07-21 14:21:34 -0700335module_exit(max7301_exit);
336
337MODULE_AUTHOR("Juergen Beisert");
338MODULE_LICENSE("GPL v2");
339MODULE_DESCRIPTION("MAX7301 SPI based GPIO-Expander");