summaryrefslogtreecommitdiffstats
path: root/drivers/i2c/busses/i2c-cbus-gpio.c
blob: bdf040fd8675c268510d496cc7d89bbbe1a0d8ae (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
/*
 * CBUS I2C driver for Nokia Internet Tablets.
 *
 * Copyright (C) 2004-2010 Nokia Corporation
 *
 * Based on code written by Juha Yrjölä, David Weinehall, Mikko Ylinen and
 * Felipe Balbi. Converted to I2C driver by Aaro Koskinen.
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License. See the file "COPYING" in the main directory of this
 * archive for more details.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 */

#include <linux/io.h>
#include <linux/i2c.h>
#include <linux/gpio.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_gpio.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/platform_data/i2c-cbus-gpio.h>

/*
 * Bit counts are derived from Nokia implementation. These should be checked
 * if other CBUS implementations appear.
 */
#define CBUS_ADDR_BITS	3
#define CBUS_REG_BITS	5

struct cbus_host {
	spinlock_t	lock;		/* host lock */
	struct device	*dev;
	int		clk_gpio;
	int		dat_gpio;
	int		sel_gpio;
};

/**
 * cbus_send_bit - sends one bit over the bus
 * @host: the host we're using
 * @bit: one bit of information to send
 */
static void cbus_send_bit(struct cbus_host *host, unsigned bit)
{
	gpio_set_value(host->dat_gpio, bit ? 1 : 0);
	gpio_set_value(host->clk_gpio, 1);
	gpio_set_value(host->clk_gpio, 0);
}

/**
 * cbus_send_data - sends @len amount of data over the bus
 * @host: the host we're using
 * @data: the data to send
 * @len: size of the transfer
 */
static void cbus_send_data(struct cbus_host *host, unsigned data, unsigned len)
{
	int i;

	for (i = len; i > 0; i--)
		cbus_send_bit(host, data & (1 << (i - 1)));
}

/**
 * cbus_receive_bit - receives one bit from the bus
 * @host: the host we're using
 */
static int cbus_receive_bit(struct cbus_host *host)
{
	int ret;

	gpio_set_value(host->clk_gpio, 1);
	ret = gpio_get_value(host->dat_gpio);
	gpio_set_value(host->clk_gpio, 0);
	return ret;
}

/**
 * cbus_receive_word - receives 16-bit word from the bus
 * @host: the host we're using
 */
static int cbus_receive_word(struct cbus_host *host)
{
	int ret = 0;
	int i;

	for (i = 16; i > 0; i--) {
		int bit = cbus_receive_bit(host);

		if (bit < 0)
			return bit;

		if (bit)
			ret |= 1 << (i - 1);
	}
	return ret;
}

/**
 * cbus_transfer - transfers data over the bus
 * @host: the host we're using
 * @rw: read/write flag
 * @dev: device address
 * @reg: register address
 * @data: if @rw == I2C_SBUS_WRITE data to send otherwise 0
 */
static int cbus_transfer(struct cbus_host *host, char rw, unsigned dev,
			 unsigned reg, unsigned data)
{
	unsigned long flags;
	int ret;

	/* We don't want interrupts disturbing our transfer */
	spin_lock_irqsave(&host->lock, flags);

	/* Reset state and start of transfer, SEL stays down during transfer */
	gpio_set_value(host->sel_gpio, 0);

	/* Set the DAT pin to output */
	gpio_direction_output(host->dat_gpio, 1);

	/* Send the device address */
	cbus_send_data(host, dev, CBUS_ADDR_BITS);

	/* Send the rw flag */
	cbus_send_bit(host, rw == I2C_SMBUS_READ);

	/* Send the register address */
	cbus_send_data(host, reg, CBUS_REG_BITS);

	if (rw == I2C_SMBUS_WRITE) {
		cbus_send_data(host, data, 16);
		ret = 0;
	} else {
		ret = gpio_direction_input(host->dat_gpio);
		if (ret) {
			dev_dbg(host->dev, "failed setting direction\n");
			goto out;
		}
		gpio_set_value(host->clk_gpio, 1);

		ret = cbus_receive_word(host);
		if (ret < 0) {
			dev_dbg(host->dev, "failed receiving data\n");
			goto out;
		}
	}

	/* Indicate end of transfer, SEL goes up until next transfer */
	gpio_set_value(host->sel_gpio, 1);
	gpio_set_value(host->clk_gpio, 1);
	gpio_set_value(host->clk_gpio, 0);

out:
	spin_unlock_irqrestore(&host->lock, flags);

	return ret;
}

static int cbus_i2c_smbus_xfer(struct i2c_adapter	*adapter,
			       u16			addr,
			       unsigned short		flags,
			       char			read_write,
			       u8			command,
			       int			size,
			       union i2c_smbus_data	*data)
{
	struct cbus_host *chost = i2c_get_adapdata(adapter);
	int ret;

	if (size != I2C_SMBUS_WORD_DATA)
		return -EINVAL;

	ret = cbus_transfer(chost, read_write == I2C_SMBUS_READ, addr,
			    command, data->word);
	if (ret < 0)
		return ret;

	if (read_write == I2C_SMBUS_READ)
		data->word = ret;

	return 0;
}

static u32 cbus_i2c_func(struct i2c_adapter *adapter)
{
	return I2C_FUNC_SMBUS_READ_WORD_DATA | I2C_FUNC_SMBUS_WRITE_WORD_DATA;
}

static const struct i2c_algorithm cbus_i2c_algo = {
	.smbus_xfer	= cbus_i2c_smbus_xfer,
	.functionality	= cbus_i2c_func,
};

static int cbus_i2c_remove(struct platform_device *pdev)
{
	struct i2c_adapter *adapter = platform_get_drvdata(pdev);

	i2c_del_adapter(adapter);

	return 0;
}

static int cbus_i2c_probe(struct platform_device *pdev)
{
	struct i2c_adapter *adapter;
	struct cbus_host *chost;
	int ret;

	adapter = devm_kzalloc(&pdev->dev, sizeof(struct i2c_adapter),
			       GFP_KERNEL);
	if (!adapter)
		return -ENOMEM;

	chost = devm_kzalloc(&pdev->dev, sizeof(*chost), GFP_KERNEL);
	if (!chost)
		return -ENOMEM;

	if (pdev->dev.of_node) {
		struct device_node *dnode = pdev->dev.of_node;
		if (of_gpio_count(dnode) != 3)
			return -ENODEV;
		chost->clk_gpio = of_get_gpio(dnode, 0);
		chost->dat_gpio = of_get_gpio(dnode, 1);
		chost->sel_gpio = of_get_gpio(dnode, 2);
	} else if (dev_get_platdata(&pdev->dev)) {
		struct i2c_cbus_platform_data *pdata =
			dev_get_platdata(&pdev->dev);
		chost->clk_gpio = pdata->clk_gpio;
		chost->dat_gpio = pdata->dat_gpio;
		chost->sel_gpio = pdata->sel_gpio;
	} else {
		return -ENODEV;
	}

	adapter->owner		= THIS_MODULE;
	adapter->class		= I2C_CLASS_HWMON;
	adapter->dev.parent	= &pdev->dev;
	adapter->dev.of_node	= pdev->dev.of_node;
	adapter->nr		= pdev->id;
	adapter->timeout	= HZ;
	adapter->algo		= &cbus_i2c_algo;
	strlcpy(adapter->name, "CBUS I2C adapter", sizeof(adapter->name));

	spin_lock_init(&chost->lock);
	chost->dev = &pdev->dev;

	ret = devm_gpio_request_one(&pdev->dev, chost->clk_gpio,
				    GPIOF_OUT_INIT_LOW, "CBUS clk");
	if (ret)
		return ret;

	ret = devm_gpio_request_one(&pdev->dev, chost->dat_gpio, GPIOF_IN,
				    "CBUS data");
	if (ret)
		return ret;

	ret = devm_gpio_request_one(&pdev->dev, chost->sel_gpio,
				    GPIOF_OUT_INIT_HIGH, "CBUS sel");
	if (ret)
		return ret;

	i2c_set_adapdata(adapter, chost);
	platform_set_drvdata(pdev, adapter);

	return i2c_add_numbered_adapter(adapter);
}

#if defined(CONFIG_OF)
static const struct of_device_id i2c_cbus_dt_ids[] = {
	{ .compatible = "i2c-cbus-gpio", },
	{ }
};
MODULE_DEVICE_TABLE(of, i2c_cbus_dt_ids);
#endif

static struct platform_driver cbus_i2c_driver = {
	.probe	= cbus_i2c_probe,
	.remove	= cbus_i2c_remove,
	.driver	= {
		.owner	= THIS_MODULE,
		.name	= "i2c-cbus-gpio",
		.of_match_table = of_match_ptr(i2c_cbus_dt_ids),
	},
};
module_platform_driver(cbus_i2c_driver);

MODULE_ALIAS("platform:i2c-cbus-gpio");
MODULE_DESCRIPTION("CBUS I2C driver");
MODULE_AUTHOR("Juha Yrjölä");
MODULE_AUTHOR("David Weinehall");
MODULE_AUTHOR("Mikko Ylinen");
MODULE_AUTHOR("Felipe Balbi");
MODULE_AUTHOR("Aaro Koskinen <aaro.koskinen@iki.fi>");
MODULE_LICENSE("GPL");