1 /*
2  * I2C multiplexer
3  *
4  * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
5  * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
6  *
7  * This module supports the PCA954x series of I2C multiplexer/switch chips
8  * made by Philips Semiconductors.
9  * This includes the:
10  *	 PCA9540, PCA9542, PCA9543, PCA9544, PCA9545, PCA9546, PCA9547
11  *	 and PCA9548.
12  *
13  * These chips are all controlled via the I2C bus itself, and all have a
14  * single 8-bit register. The upstream "parent" bus fans out to two,
15  * four, or eight downstream busses or channels; which of these
16  * are selected is determined by the chip type and register contents. A
17  * mux can select only one sub-bus at a time; a switch can select any
18  * combination simultaneously.
19  *
20  * Based on:
21  *	pca954x.c from Kumar Gala <galak@kernel.crashing.org>
22  * Copyright (C) 2006
23  *
24  * Based on:
25  *	pca954x.c from Ken Harrenstien
26  * Copyright (C) 2004 Google, Inc. (Ken Harrenstien)
27  *
28  * Based on:
29  *	i2c-virtual_cb.c from Brian Kuschak <bkuschak@yahoo.com>
30  * and
31  *	pca9540.c from Jean Delvare <khali@linux-fr.org>.
32  *
33  * This file is licensed under the terms of the GNU General Public
34  * License version 2. This program is licensed "as is" without any
35  * warranty of any kind, whether express or implied.
36  */
37 
38 #include <linux/module.h>
39 #include <linux/init.h>
40 #include <linux/slab.h>
41 #include <linux/device.h>
42 #include <linux/i2c.h>
43 #include <linux/i2c-mux.h>
44 
45 #include <linux/i2c/pca954x.h>
46 
47 #define PCA954X_MAX_NCHANS 8
48 
49 enum pca_type {
50 	pca_9540,
51 	pca_9542,
52 	pca_9543,
53 	pca_9544,
54 	pca_9545,
55 	pca_9546,
56 	pca_9547,
57 	pca_9548,
58 };
59 
60 struct pca954x {
61 	enum pca_type type;
62 	struct i2c_adapter *virt_adaps[PCA954X_MAX_NCHANS];
63 
64 	u8 last_chan;		/* last register value */
65 };
66 
67 struct chip_desc {
68 	u8 nchans;
69 	u8 enable;	/* used for muxes only */
70 	enum muxtype {
71 		pca954x_ismux = 0,
72 		pca954x_isswi
73 	} muxtype;
74 };
75 
76 /* Provide specs for the PCA954x types we know about */
77 static const struct chip_desc chips[] = {
78 	[pca_9540] = {
79 		.nchans = 2,
80 		.enable = 0x4,
81 		.muxtype = pca954x_ismux,
82 	},
83 	[pca_9543] = {
84 		.nchans = 2,
85 		.muxtype = pca954x_isswi,
86 	},
87 	[pca_9544] = {
88 		.nchans = 4,
89 		.enable = 0x4,
90 		.muxtype = pca954x_ismux,
91 	},
92 	[pca_9545] = {
93 		.nchans = 4,
94 		.muxtype = pca954x_isswi,
95 	},
96 	[pca_9547] = {
97 		.nchans = 8,
98 		.enable = 0x8,
99 		.muxtype = pca954x_ismux,
100 	},
101 	[pca_9548] = {
102 		.nchans = 8,
103 		.muxtype = pca954x_isswi,
104 	},
105 };
106 
107 static const struct i2c_device_id pca954x_id[] = {
108 	{ "pca9540", pca_9540 },
109 	{ "pca9542", pca_9540 },
110 	{ "pca9543", pca_9543 },
111 	{ "pca9544", pca_9544 },
112 	{ "pca9545", pca_9545 },
113 	{ "pca9546", pca_9545 },
114 	{ "pca9547", pca_9547 },
115 	{ "pca9548", pca_9548 },
116 	{ }
117 };
118 MODULE_DEVICE_TABLE(i2c, pca954x_id);
119 
120 /* Write to mux register. Don't use i2c_transfer()/i2c_smbus_xfer()
121    for this as they will try to lock adapter a second time */
122 static int pca954x_reg_write(struct i2c_adapter *adap,
123 			     struct i2c_client *client, u8 val)
124 {
125 	int ret = -ENODEV;
126 
127 	if (adap->algo->master_xfer) {
128 		struct i2c_msg msg;
129 		char buf[1];
130 
131 		msg.addr = client->addr;
132 		msg.flags = 0;
133 		msg.len = 1;
134 		buf[0] = val;
135 		msg.buf = buf;
136 		ret = adap->algo->master_xfer(adap, &msg, 1);
137 	} else {
138 		union i2c_smbus_data data;
139 		ret = adap->algo->smbus_xfer(adap, client->addr,
140 					     client->flags,
141 					     I2C_SMBUS_WRITE,
142 					     val, I2C_SMBUS_BYTE, &data);
143 	}
144 
145 	return ret;
146 }
147 
148 static int pca954x_select_chan(struct i2c_adapter *adap,
149 			       void *client, u32 chan)
150 {
151 	struct pca954x *data = i2c_get_clientdata(client);
152 	const struct chip_desc *chip = &chips[data->type];
153 	u8 regval;
154 	int ret = 0;
155 
156 	/* we make switches look like muxes, not sure how to be smarter */
157 	if (chip->muxtype == pca954x_ismux)
158 		regval = chan | chip->enable;
159 	else
160 		regval = 1 << chan;
161 
162 	/* Only select the channel if its different from the last channel */
163 	if (data->last_chan != regval) {
164 		ret = pca954x_reg_write(adap, client, regval);
165 		data->last_chan = regval;
166 	}
167 
168 	return ret;
169 }
170 
171 static int pca954x_deselect_mux(struct i2c_adapter *adap,
172 				void *client, u32 chan)
173 {
174 	struct pca954x *data = i2c_get_clientdata(client);
175 
176 	/* Deselect active channel */
177 	data->last_chan = 0;
178 	return pca954x_reg_write(adap, client, data->last_chan);
179 }
180 
181 /*
182  * I2C init/probing/exit functions
183  */
184 static int pca954x_probe(struct i2c_client *client,
185 			 const struct i2c_device_id *id)
186 {
187 	struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
188 	struct pca954x_platform_data *pdata = dev_get_platdata(&client->dev);
189 	int num, force, class;
190 	struct pca954x *data;
191 	int ret = -ENODEV;
192 
193 	if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE))
194 		goto err;
195 
196 	data = kzalloc(sizeof(struct pca954x), GFP_KERNEL);
197 	if (!data) {
198 		ret = -ENOMEM;
199 		goto err;
200 	}
201 
202 	i2c_set_clientdata(client, data);
203 
204 	/* Write the mux register at addr to verify
205 	 * that the mux is in fact present. This also
206 	 * initializes the mux to disconnected state.
207 	 */
208 	if (i2c_smbus_write_byte(client, 0) < 0) {
209 		dev_warn(&client->dev, "probe failed\n");
210 		goto exit_free;
211 	}
212 
213 	data->type = id->driver_data;
214 	data->last_chan = 0;		   /* force the first selection */
215 
216 	/* Now create an adapter for each channel */
217 	for (num = 0; num < chips[data->type].nchans; num++) {
218 		force = 0;			  /* dynamic adap number */
219 		class = 0;			  /* no class by default */
220 		if (pdata) {
221 			if (num < pdata->num_modes) {
222 				/* force static number */
223 				force = pdata->modes[num].adap_id;
224 				class = pdata->modes[num].class;
225 			} else
226 				/* discard unconfigured channels */
227 				break;
228 		}
229 
230 		data->virt_adaps[num] =
231 			i2c_add_mux_adapter(adap, &client->dev, client,
232 				force, num, class, pca954x_select_chan,
233 				(pdata && pdata->modes[num].deselect_on_exit)
234 					? pca954x_deselect_mux : NULL);
235 
236 		if (data->virt_adaps[num] == NULL) {
237 			ret = -ENODEV;
238 			dev_err(&client->dev,
239 				"failed to register multiplexed adapter"
240 				" %d as bus %d\n", num, force);
241 			goto virt_reg_failed;
242 		}
243 	}
244 
245 	dev_info(&client->dev,
246 		 "registered %d multiplexed busses for I2C %s %s\n",
247 		 num, chips[data->type].muxtype == pca954x_ismux
248 				? "mux" : "switch", client->name);
249 
250 	return 0;
251 
252 virt_reg_failed:
253 	for (num--; num >= 0; num--)
254 		i2c_del_mux_adapter(data->virt_adaps[num]);
255 exit_free:
256 	kfree(data);
257 err:
258 	return ret;
259 }
260 
261 static int pca954x_remove(struct i2c_client *client)
262 {
263 	struct pca954x *data = i2c_get_clientdata(client);
264 	const struct chip_desc *chip = &chips[data->type];
265 	int i;
266 
267 	for (i = 0; i < chip->nchans; ++i)
268 		if (data->virt_adaps[i]) {
269 			i2c_del_mux_adapter(data->virt_adaps[i]);
270 			data->virt_adaps[i] = NULL;
271 		}
272 
273 	kfree(data);
274 	return 0;
275 }
276 
277 static struct i2c_driver pca954x_driver = {
278 	.driver		= {
279 		.name	= "pca954x",
280 		.owner	= THIS_MODULE,
281 	},
282 	.probe		= pca954x_probe,
283 	.remove		= pca954x_remove,
284 	.id_table	= pca954x_id,
285 };
286 
287 module_i2c_driver(pca954x_driver);
288 
289 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
290 MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
291 MODULE_LICENSE("GPL v2");
292