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 <jdelvare@suse.de>.
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/device.h>
39 #include <linux/gpio/consumer.h>
40 #include <linux/i2c.h>
41 #include <linux/i2c-mux.h>
42 #include <linux/i2c/pca954x.h>
43 #include <linux/module.h>
44 #include <linux/of.h>
45 #include <linux/pm.h>
46 #include <linux/slab.h>
47 
48 #define PCA954X_MAX_NCHANS 8
49 
50 enum pca_type {
51 	pca_9540,
52 	pca_9542,
53 	pca_9543,
54 	pca_9544,
55 	pca_9545,
56 	pca_9546,
57 	pca_9547,
58 	pca_9548,
59 };
60 
61 struct pca954x {
62 	enum pca_type type;
63 
64 	u8 last_chan;		/* last register value */
65 	u8 deselect;
66 	struct i2c_client *client;
67 };
68 
69 struct chip_desc {
70 	u8 nchans;
71 	u8 enable;	/* used for muxes only */
72 	enum muxtype {
73 		pca954x_ismux = 0,
74 		pca954x_isswi
75 	} muxtype;
76 };
77 
78 /* Provide specs for the PCA954x types we know about */
79 static const struct chip_desc chips[] = {
80 	[pca_9540] = {
81 		.nchans = 2,
82 		.enable = 0x4,
83 		.muxtype = pca954x_ismux,
84 	},
85 	[pca_9543] = {
86 		.nchans = 2,
87 		.muxtype = pca954x_isswi,
88 	},
89 	[pca_9544] = {
90 		.nchans = 4,
91 		.enable = 0x4,
92 		.muxtype = pca954x_ismux,
93 	},
94 	[pca_9545] = {
95 		.nchans = 4,
96 		.muxtype = pca954x_isswi,
97 	},
98 	[pca_9547] = {
99 		.nchans = 8,
100 		.enable = 0x8,
101 		.muxtype = pca954x_ismux,
102 	},
103 	[pca_9548] = {
104 		.nchans = 8,
105 		.muxtype = pca954x_isswi,
106 	},
107 };
108 
109 static const struct i2c_device_id pca954x_id[] = {
110 	{ "pca9540", pca_9540 },
111 	{ "pca9542", pca_9540 },
112 	{ "pca9543", pca_9543 },
113 	{ "pca9544", pca_9544 },
114 	{ "pca9545", pca_9545 },
115 	{ "pca9546", pca_9545 },
116 	{ "pca9547", pca_9547 },
117 	{ "pca9548", pca_9548 },
118 	{ }
119 };
120 MODULE_DEVICE_TABLE(i2c, pca954x_id);
121 
122 /* Write to mux register. Don't use i2c_transfer()/i2c_smbus_xfer()
123    for this as they will try to lock adapter a second time */
124 static int pca954x_reg_write(struct i2c_adapter *adap,
125 			     struct i2c_client *client, u8 val)
126 {
127 	int ret = -ENODEV;
128 
129 	if (adap->algo->master_xfer) {
130 		struct i2c_msg msg;
131 		char buf[1];
132 
133 		msg.addr = client->addr;
134 		msg.flags = 0;
135 		msg.len = 1;
136 		buf[0] = val;
137 		msg.buf = buf;
138 		ret = __i2c_transfer(adap, &msg, 1);
139 	} else {
140 		union i2c_smbus_data data;
141 		ret = adap->algo->smbus_xfer(adap, client->addr,
142 					     client->flags,
143 					     I2C_SMBUS_WRITE,
144 					     val, I2C_SMBUS_BYTE, &data);
145 	}
146 
147 	return ret;
148 }
149 
150 static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan)
151 {
152 	struct pca954x *data = i2c_mux_priv(muxc);
153 	struct i2c_client *client = data->client;
154 	const struct chip_desc *chip = &chips[data->type];
155 	u8 regval;
156 	int ret = 0;
157 
158 	/* we make switches look like muxes, not sure how to be smarter */
159 	if (chip->muxtype == pca954x_ismux)
160 		regval = chan | chip->enable;
161 	else
162 		regval = 1 << chan;
163 
164 	/* Only select the channel if its different from the last channel */
165 	if (data->last_chan != regval) {
166 		ret = pca954x_reg_write(muxc->parent, client, regval);
167 		data->last_chan = regval;
168 	}
169 
170 	return ret;
171 }
172 
173 static int pca954x_deselect_mux(struct i2c_mux_core *muxc, u32 chan)
174 {
175 	struct pca954x *data = i2c_mux_priv(muxc);
176 	struct i2c_client *client = data->client;
177 
178 	if (!(data->deselect & (1 << chan)))
179 		return 0;
180 
181 	/* Deselect active channel */
182 	data->last_chan = 0;
183 	return pca954x_reg_write(muxc->parent, client, data->last_chan);
184 }
185 
186 /*
187  * I2C init/probing/exit functions
188  */
189 static int pca954x_probe(struct i2c_client *client,
190 			 const struct i2c_device_id *id)
191 {
192 	struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
193 	struct pca954x_platform_data *pdata = dev_get_platdata(&client->dev);
194 	struct device_node *of_node = client->dev.of_node;
195 	bool idle_disconnect_dt;
196 	struct gpio_desc *gpio;
197 	int num, force, class;
198 	struct i2c_mux_core *muxc;
199 	struct pca954x *data;
200 	int ret;
201 
202 	if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE))
203 		return -ENODEV;
204 
205 	muxc = i2c_mux_alloc(adap, &client->dev,
206 			     PCA954X_MAX_NCHANS, sizeof(*data), 0,
207 			     pca954x_select_chan, pca954x_deselect_mux);
208 	if (!muxc)
209 		return -ENOMEM;
210 	data = i2c_mux_priv(muxc);
211 
212 	i2c_set_clientdata(client, muxc);
213 	data->client = client;
214 
215 	/* Get the mux out of reset if a reset GPIO is specified. */
216 	gpio = devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_LOW);
217 	if (IS_ERR(gpio))
218 		return PTR_ERR(gpio);
219 
220 	/* Write the mux register at addr to verify
221 	 * that the mux is in fact present. This also
222 	 * initializes the mux to disconnected state.
223 	 */
224 	if (i2c_smbus_write_byte(client, 0) < 0) {
225 		dev_warn(&client->dev, "probe failed\n");
226 		return -ENODEV;
227 	}
228 
229 	data->type = id->driver_data;
230 	data->last_chan = 0;		   /* force the first selection */
231 
232 	idle_disconnect_dt = of_node &&
233 		of_property_read_bool(of_node, "i2c-mux-idle-disconnect");
234 
235 	/* Now create an adapter for each channel */
236 	for (num = 0; num < chips[data->type].nchans; num++) {
237 		bool idle_disconnect_pd = false;
238 
239 		force = 0;			  /* dynamic adap number */
240 		class = 0;			  /* no class by default */
241 		if (pdata) {
242 			if (num < pdata->num_modes) {
243 				/* force static number */
244 				force = pdata->modes[num].adap_id;
245 				class = pdata->modes[num].class;
246 			} else
247 				/* discard unconfigured channels */
248 				break;
249 			idle_disconnect_pd = pdata->modes[num].deselect_on_exit;
250 			data->deselect |= (idle_disconnect_pd
251 					   || idle_disconnect_dt) << num;
252 		}
253 
254 		ret = i2c_mux_add_adapter(muxc, force, num, class);
255 
256 		if (ret) {
257 			dev_err(&client->dev,
258 				"failed to register multiplexed adapter"
259 				" %d as bus %d\n", num, force);
260 			goto virt_reg_failed;
261 		}
262 	}
263 
264 	dev_info(&client->dev,
265 		 "registered %d multiplexed busses for I2C %s %s\n",
266 		 num, chips[data->type].muxtype == pca954x_ismux
267 				? "mux" : "switch", client->name);
268 
269 	return 0;
270 
271 virt_reg_failed:
272 	i2c_mux_del_adapters(muxc);
273 	return ret;
274 }
275 
276 static int pca954x_remove(struct i2c_client *client)
277 {
278 	struct i2c_mux_core *muxc = i2c_get_clientdata(client);
279 
280 	i2c_mux_del_adapters(muxc);
281 	return 0;
282 }
283 
284 #ifdef CONFIG_PM_SLEEP
285 static int pca954x_resume(struct device *dev)
286 {
287 	struct i2c_client *client = to_i2c_client(dev);
288 	struct i2c_mux_core *muxc = i2c_get_clientdata(client);
289 	struct pca954x *data = i2c_mux_priv(muxc);
290 
291 	data->last_chan = 0;
292 	return i2c_smbus_write_byte(client, 0);
293 }
294 #endif
295 
296 static SIMPLE_DEV_PM_OPS(pca954x_pm, NULL, pca954x_resume);
297 
298 static struct i2c_driver pca954x_driver = {
299 	.driver		= {
300 		.name	= "pca954x",
301 		.pm	= &pca954x_pm,
302 	},
303 	.probe		= pca954x_probe,
304 	.remove		= pca954x_remove,
305 	.id_table	= pca954x_id,
306 };
307 
308 module_i2c_driver(pca954x_driver);
309 
310 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
311 MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
312 MODULE_LICENSE("GPL v2");
313