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1 /**
2  * Copyright (C) 2006 Juergen Beisert, Pengutronix
3  * Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
4  * Copyright (C) 2009 Wolfram Sang, Pengutronix
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  * The Maxim MAX7300/1 device is an I2C/SPI driven GPIO expander. There are
11  * 28 GPIOs. 8 of them can trigger an interrupt. See datasheet for more
12  * details
13  * Note:
14  * - DIN must be stable at the rising edge of clock.
15  * - when writing:
16  *   - always clock in 16 clocks at once
17  *   - at DIN: D15 first, D0 last
18  *   - D0..D7 = databyte, D8..D14 = commandbyte
19  *   - D15 = low -> write command
20  * - when reading
21  *   - always clock in 16 clocks at once
22  *   - at DIN: D15 first, D0 last
23  *   - D0..D7 = dummy, D8..D14 = register address
24  *   - D15 = high -> read command
25  *   - raise CS and assert it again
26  *   - always clock in 16 clocks at once
27  *   - at DOUT: D15 first, D0 last
28  *   - D0..D7 contains the data from the first cycle
29  *
30  * The driver exports a standard gpiochip interface
31  */
32 
33 #include <linux/module.h>
34 #include <linux/init.h>
35 #include <linux/platform_device.h>
36 #include <linux/mutex.h>
37 #include <linux/spi/max7301.h>
38 #include <linux/gpio.h>
39 #include <linux/slab.h>
40 
41 /*
42  * Pin configurations, see MAX7301 datasheet page 6
43  */
44 #define PIN_CONFIG_MASK 0x03
45 #define PIN_CONFIG_IN_PULLUP 0x03
46 #define PIN_CONFIG_IN_WO_PULLUP 0x02
47 #define PIN_CONFIG_OUT 0x01
48 
49 #define PIN_NUMBER 28
50 
max7301_direction_input(struct gpio_chip * chip,unsigned offset)51 static int max7301_direction_input(struct gpio_chip *chip, unsigned offset)
52 {
53 	struct max7301 *ts = gpiochip_get_data(chip);
54 	u8 *config;
55 	u8 offset_bits, pin_config;
56 	int ret;
57 
58 	/* First 4 pins are unused in the controller */
59 	offset += 4;
60 	offset_bits = (offset & 3) << 1;
61 
62 	config = &ts->port_config[offset >> 2];
63 
64 	if (ts->input_pullup_active & BIT(offset))
65 		pin_config = PIN_CONFIG_IN_PULLUP;
66 	else
67 		pin_config = PIN_CONFIG_IN_WO_PULLUP;
68 
69 	mutex_lock(&ts->lock);
70 
71 	*config = (*config & ~(PIN_CONFIG_MASK << offset_bits))
72 			   | (pin_config << offset_bits);
73 
74 	ret = ts->write(ts->dev, 0x08 + (offset >> 2), *config);
75 
76 	mutex_unlock(&ts->lock);
77 
78 	return ret;
79 }
80 
__max7301_set(struct max7301 * ts,unsigned offset,int value)81 static int __max7301_set(struct max7301 *ts, unsigned offset, int value)
82 {
83 	if (value) {
84 		ts->out_level |= 1 << offset;
85 		return ts->write(ts->dev, 0x20 + offset, 0x01);
86 	} else {
87 		ts->out_level &= ~(1 << offset);
88 		return ts->write(ts->dev, 0x20 + offset, 0x00);
89 	}
90 }
91 
max7301_direction_output(struct gpio_chip * chip,unsigned offset,int value)92 static int max7301_direction_output(struct gpio_chip *chip, unsigned offset,
93 				    int value)
94 {
95 	struct max7301 *ts = gpiochip_get_data(chip);
96 	u8 *config;
97 	u8 offset_bits;
98 	int ret;
99 
100 	/* First 4 pins are unused in the controller */
101 	offset += 4;
102 	offset_bits = (offset & 3) << 1;
103 
104 	config = &ts->port_config[offset >> 2];
105 
106 	mutex_lock(&ts->lock);
107 
108 	*config = (*config & ~(PIN_CONFIG_MASK << offset_bits))
109 			   | (PIN_CONFIG_OUT << offset_bits);
110 
111 	ret = __max7301_set(ts, offset, value);
112 
113 	if (!ret)
114 		ret = ts->write(ts->dev, 0x08 + (offset >> 2), *config);
115 
116 	mutex_unlock(&ts->lock);
117 
118 	return ret;
119 }
120 
max7301_get(struct gpio_chip * chip,unsigned offset)121 static int max7301_get(struct gpio_chip *chip, unsigned offset)
122 {
123 	struct max7301 *ts = gpiochip_get_data(chip);
124 	int config, level = -EINVAL;
125 
126 	/* First 4 pins are unused in the controller */
127 	offset += 4;
128 
129 	mutex_lock(&ts->lock);
130 
131 	config = (ts->port_config[offset >> 2] >> ((offset & 3) << 1))
132 			& PIN_CONFIG_MASK;
133 
134 	switch (config) {
135 	case PIN_CONFIG_OUT:
136 		/* Output: return cached level */
137 		level =  !!(ts->out_level & (1 << offset));
138 		break;
139 	case PIN_CONFIG_IN_WO_PULLUP:
140 	case PIN_CONFIG_IN_PULLUP:
141 		/* Input: read out */
142 		level = ts->read(ts->dev, 0x20 + offset) & 0x01;
143 	}
144 	mutex_unlock(&ts->lock);
145 
146 	return level;
147 }
148 
max7301_set(struct gpio_chip * chip,unsigned offset,int value)149 static void max7301_set(struct gpio_chip *chip, unsigned offset, int value)
150 {
151 	struct max7301 *ts = gpiochip_get_data(chip);
152 
153 	/* First 4 pins are unused in the controller */
154 	offset += 4;
155 
156 	mutex_lock(&ts->lock);
157 
158 	__max7301_set(ts, offset, value);
159 
160 	mutex_unlock(&ts->lock);
161 }
162 
__max730x_probe(struct max7301 * ts)163 int __max730x_probe(struct max7301 *ts)
164 {
165 	struct device *dev = ts->dev;
166 	struct max7301_platform_data *pdata;
167 	int i, ret;
168 
169 	pdata = dev_get_platdata(dev);
170 
171 	mutex_init(&ts->lock);
172 	dev_set_drvdata(dev, ts);
173 
174 	/* Power up the chip and disable IRQ output */
175 	ts->write(dev, 0x04, 0x01);
176 
177 	if (pdata) {
178 		ts->input_pullup_active = pdata->input_pullup_active;
179 		ts->chip.base = pdata->base;
180 	} else {
181 		ts->chip.base = -1;
182 	}
183 	ts->chip.label = dev->driver->name;
184 
185 	ts->chip.direction_input = max7301_direction_input;
186 	ts->chip.get = max7301_get;
187 	ts->chip.direction_output = max7301_direction_output;
188 	ts->chip.set = max7301_set;
189 
190 	ts->chip.ngpio = PIN_NUMBER;
191 	ts->chip.can_sleep = true;
192 	ts->chip.parent = dev;
193 	ts->chip.owner = THIS_MODULE;
194 
195 	ret = gpiochip_add_data(&ts->chip, ts);
196 	if (ret)
197 		goto exit_destroy;
198 
199 	/*
200 	 * initialize pullups according to platform data and cache the
201 	 * register values for later use.
202 	 */
203 	for (i = 1; i < 8; i++) {
204 		int j;
205 		/*
206 		 * initialize port_config with "0xAA", which means
207 		 * input with internal pullup disabled. This is needed
208 		 * to avoid writing zeros (in the inner for loop),
209 		 * which is not allowed according to the datasheet.
210 		 */
211 		ts->port_config[i] = 0xAA;
212 		for (j = 0; j < 4; j++) {
213 			int offset = (i - 1) * 4 + j;
214 			ret = max7301_direction_input(&ts->chip, offset);
215 			if (ret)
216 				goto exit_destroy;
217 		}
218 	}
219 
220 	return ret;
221 
222 exit_destroy:
223 	mutex_destroy(&ts->lock);
224 	return ret;
225 }
226 EXPORT_SYMBOL_GPL(__max730x_probe);
227 
__max730x_remove(struct device * dev)228 int __max730x_remove(struct device *dev)
229 {
230 	struct max7301 *ts = dev_get_drvdata(dev);
231 
232 	if (ts == NULL)
233 		return -ENODEV;
234 
235 	/* Power down the chip and disable IRQ output */
236 	ts->write(dev, 0x04, 0x00);
237 	gpiochip_remove(&ts->chip);
238 	mutex_destroy(&ts->lock);
239 	return 0;
240 }
241 EXPORT_SYMBOL_GPL(__max730x_remove);
242 
243 MODULE_AUTHOR("Juergen Beisert, Wolfram Sang");
244 MODULE_LICENSE("GPL v2");
245 MODULE_DESCRIPTION("MAX730x GPIO-Expanders, generic parts");
246