1/*
2 * CBUS I2C driver for Nokia Internet Tablets.
3 *
4 * Copyright (C) 2004-2010 Nokia Corporation
5 *
6 * Based on code written by Juha Yrj��l��, David Weinehall, Mikko Ylinen and
7 * Felipe Balbi. Converted to I2C driver by Aaro Koskinen.
8 *
9 * This file is subject to the terms and conditions of the GNU General
10 * Public License. See the file "COPYING" in the main directory of this
11 * archive for more details.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 */
18
19#include <linux/io.h>
20#include <linux/i2c.h>
21#include <linux/slab.h>
22#include <linux/delay.h>
23#include <linux/errno.h>
24#include <linux/kernel.h>
25#include <linux/module.h>
26#include <linux/gpio/consumer.h>
27#include <linux/interrupt.h>
28#include <linux/platform_device.h>
29
30/*
31 * Bit counts are derived from Nokia implementation. These should be checked
32 * if other CBUS implementations appear.
33 */
34#define CBUS_ADDR_BITS	3
35#define CBUS_REG_BITS	5
36
37struct cbus_host {
38	spinlock_t	lock;		/* host lock */
39	struct device	*dev;
40	struct gpio_desc *clk;
41	struct gpio_desc *dat;
42	struct gpio_desc *sel;
43};
44
45/**
46 * cbus_send_bit - sends one bit over the bus
47 * @host: the host we're using
48 * @bit: one bit of information to send
49 */
50static void cbus_send_bit(struct cbus_host *host, unsigned bit)
51{
52	gpiod_set_value(host->dat, bit ? 1 : 0);
53	gpiod_set_value(host->clk, 1);
54	gpiod_set_value(host->clk, 0);
55}
56
57/**
58 * cbus_send_data - sends @len amount of data over the bus
59 * @host: the host we're using
60 * @data: the data to send
61 * @len: size of the transfer
62 */
63static void cbus_send_data(struct cbus_host *host, unsigned data, unsigned len)
64{
65	int i;
66
67	for (i = len; i > 0; i--)
68		cbus_send_bit(host, data & (1 << (i - 1)));
69}
70
71/**
72 * cbus_receive_bit - receives one bit from the bus
73 * @host: the host we're using
74 */
75static int cbus_receive_bit(struct cbus_host *host)
76{
77	int ret;
78
79	gpiod_set_value(host->clk, 1);
80	ret = gpiod_get_value(host->dat);
81	gpiod_set_value(host->clk, 0);
82	return ret;
83}
84
85/**
86 * cbus_receive_word - receives 16-bit word from the bus
87 * @host: the host we're using
88 */
89static int cbus_receive_word(struct cbus_host *host)
90{
91	int ret = 0;
92	int i;
93
94	for (i = 16; i > 0; i--) {
95		int bit = cbus_receive_bit(host);
96
97		if (bit < 0)
98			return bit;
99
100		if (bit)
101			ret |= 1 << (i - 1);
102	}
103	return ret;
104}
105
106/**
107 * cbus_transfer - transfers data over the bus
108 * @host: the host we're using
109 * @rw: read/write flag
110 * @dev: device address
111 * @reg: register address
112 * @data: if @rw == I2C_SBUS_WRITE data to send otherwise 0
113 */
114static int cbus_transfer(struct cbus_host *host, char rw, unsigned dev,
115			 unsigned reg, unsigned data)
116{
117	unsigned long flags;
118	int ret;
119
120	/* We don't want interrupts disturbing our transfer */
121	spin_lock_irqsave(&host->lock, flags);
122
123	/* Reset state and start of transfer, SEL stays down during transfer */
124	gpiod_set_value(host->sel, 0);
125
126	/* Set the DAT pin to output */
127	gpiod_direction_output(host->dat, 1);
128
129	/* Send the device address */
130	cbus_send_data(host, dev, CBUS_ADDR_BITS);
131
132	/* Send the rw flag */
133	cbus_send_bit(host, rw == I2C_SMBUS_READ);
134
135	/* Send the register address */
136	cbus_send_data(host, reg, CBUS_REG_BITS);
137
138	if (rw == I2C_SMBUS_WRITE) {
139		cbus_send_data(host, data, 16);
140		ret = 0;
141	} else {
142		ret = gpiod_direction_input(host->dat);
143		if (ret) {
144			dev_dbg(host->dev, "failed setting direction\n");
145			goto out;
146		}
147		gpiod_set_value(host->clk, 1);
148
149		ret = cbus_receive_word(host);
150		if (ret < 0) {
151			dev_dbg(host->dev, "failed receiving data\n");
152			goto out;
153		}
154	}
155
156	/* Indicate end of transfer, SEL goes up until next transfer */
157	gpiod_set_value(host->sel, 1);
158	gpiod_set_value(host->clk, 1);
159	gpiod_set_value(host->clk, 0);
160
161out:
162	spin_unlock_irqrestore(&host->lock, flags);
163
164	return ret;
165}
166
167static int cbus_i2c_smbus_xfer(struct i2c_adapter	*adapter,
168			       u16			addr,
169			       unsigned short		flags,
170			       char			read_write,
171			       u8			command,
172			       int			size,
173			       union i2c_smbus_data	*data)
174{
175	struct cbus_host *chost = i2c_get_adapdata(adapter);
176	int ret;
177
178	if (size != I2C_SMBUS_WORD_DATA)
179		return -EINVAL;
180
181	ret = cbus_transfer(chost, read_write == I2C_SMBUS_READ, addr,
182			    command, data->word);
183	if (ret < 0)
184		return ret;
185
186	if (read_write == I2C_SMBUS_READ)
187		data->word = ret;
188
189	return 0;
190}
191
192static u32 cbus_i2c_func(struct i2c_adapter *adapter)
193{
194	return I2C_FUNC_SMBUS_READ_WORD_DATA | I2C_FUNC_SMBUS_WRITE_WORD_DATA;
195}
196
197static const struct i2c_algorithm cbus_i2c_algo = {
198	.smbus_xfer		= cbus_i2c_smbus_xfer,
199	.smbus_xfer_atomic	= cbus_i2c_smbus_xfer,
200	.functionality		= cbus_i2c_func,
201};
202
203static void cbus_i2c_remove(struct platform_device *pdev)
204{
205	struct i2c_adapter *adapter = platform_get_drvdata(pdev);
206
207	i2c_del_adapter(adapter);
208}
209
210static int cbus_i2c_probe(struct platform_device *pdev)
211{
212	struct i2c_adapter *adapter;
213	struct cbus_host *chost;
214
215	adapter = devm_kzalloc(&pdev->dev, sizeof(struct i2c_adapter),
216			       GFP_KERNEL);
217	if (!adapter)
218		return -ENOMEM;
219
220	chost = devm_kzalloc(&pdev->dev, sizeof(*chost), GFP_KERNEL);
221	if (!chost)
222		return -ENOMEM;
223
224	if (gpiod_count(&pdev->dev, NULL) != 3)
225		return -ENODEV;
226	chost->clk = devm_gpiod_get_index(&pdev->dev, NULL, 0, GPIOD_OUT_LOW);
227	if (IS_ERR(chost->clk))
228		return PTR_ERR(chost->clk);
229	chost->dat = devm_gpiod_get_index(&pdev->dev, NULL, 1, GPIOD_IN);
230	if (IS_ERR(chost->dat))
231		return PTR_ERR(chost->dat);
232	chost->sel = devm_gpiod_get_index(&pdev->dev, NULL, 2, GPIOD_OUT_HIGH);
233	if (IS_ERR(chost->sel))
234		return PTR_ERR(chost->sel);
235	gpiod_set_consumer_name(chost->clk, "CBUS clk");
236	gpiod_set_consumer_name(chost->dat, "CBUS dat");
237	gpiod_set_consumer_name(chost->sel, "CBUS sel");
238
239	adapter->owner		= THIS_MODULE;
240	adapter->class		= I2C_CLASS_HWMON;
241	adapter->dev.parent	= &pdev->dev;
242	adapter->dev.of_node	= pdev->dev.of_node;
243	adapter->nr		= pdev->id;
244	adapter->timeout	= HZ;
245	adapter->algo		= &cbus_i2c_algo;
246	strscpy(adapter->name, "CBUS I2C adapter", sizeof(adapter->name));
247
248	spin_lock_init(&chost->lock);
249	chost->dev = &pdev->dev;
250
251	i2c_set_adapdata(adapter, chost);
252	platform_set_drvdata(pdev, adapter);
253
254	return i2c_add_numbered_adapter(adapter);
255}
256
257#if defined(CONFIG_OF)
258static const struct of_device_id i2c_cbus_dt_ids[] = {
259	{ .compatible = "i2c-cbus-gpio", },
260	{ }
261};
262MODULE_DEVICE_TABLE(of, i2c_cbus_dt_ids);
263#endif
264
265static struct platform_driver cbus_i2c_driver = {
266	.probe	= cbus_i2c_probe,
267	.remove_new = cbus_i2c_remove,
268	.driver	= {
269		.name	= "i2c-cbus-gpio",
270		.of_match_table = of_match_ptr(i2c_cbus_dt_ids),
271	},
272};
273module_platform_driver(cbus_i2c_driver);
274
275MODULE_ALIAS("platform:i2c-cbus-gpio");
276MODULE_DESCRIPTION("CBUS I2C driver");
277MODULE_AUTHOR("Juha Yrj��l��");
278MODULE_AUTHOR("David Weinehall");
279MODULE_AUTHOR("Mikko Ylinen");
280MODULE_AUTHOR("Felipe Balbi");
281MODULE_AUTHOR("Aaro Koskinen <aaro.koskinen@iki.fi>");
282MODULE_LICENSE("GPL");
283