6  * Author: Guenter Roeck <linux@roeck-us.net>
11  *  Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
12  *  Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
23 #include <linux/i2c-mux.h>
36  * single-channel I2C bus multiplexer.
40  * that only one of the masters is instantiated at any given time.
68 #define ARB2_TIMEOUT	(HZ / 4)	/* 250 ms until acquisition failure */
97  * as they will try to lock the adapter a second time.
101 	struct i2c_adapter *adap = client->adapter;  in pca9541_reg_write()
104 	return __i2c_smbus_xfer(adap, client->addr, client->flags,  in pca9541_reg_write()
111  * as they will try to lock adapter a second time.
115 	struct i2c_adapter *adap = client->adapter;  in pca9541_reg_read()
119 	ret = __i2c_smbus_xfer(adap, client->addr, client->flags,  in pca9541_reg_read()
142  * Arbitration is defined as a two-step process. A bus master can only activate
144  * This multi-step process ensures that access contention is resolved
149  * ----------------------------------------------------
150  * off	-		yes		wait for arbitration timeout or
154  * on	yes		-		done
155  * on	no		-		wait for arbitration timeout or
159  * request ownership at the same time. In this case, one master will turn on
196 		    || time_is_before_eq_jiffies(data->arb_timeout)) {  in pca9541_arbitrate()
205 			data->select_timeout = SELECT_DELAY_SHORT;  in pca9541_arbitrate()
209 			 * Set extra long timeout to give it time to acquire it.  in pca9541_arbitrate()
211 			data->select_timeout = SELECT_DELAY_LONG * 2;  in pca9541_arbitrate()
215 		 * Bus is on, and we own it. We are done with acquisition.  in pca9541_arbitrate()
230 		data->select_timeout = SELECT_DELAY_LONG;  in pca9541_arbitrate()
231 		if (time_is_before_eq_jiffies(data->arb_timeout)) {  in pca9541_arbitrate()
232 			/* Time is up, take the bus and reset it. */  in pca9541_arbitrate()
252 	struct i2c_client *client = data->client;  in pca9541_select_chan()
255 		/* give up after this time */  in pca9541_select_chan()
257 	data->arb_timeout = jiffies + ARB_TIMEOUT;  in pca9541_select_chan()
258 		/* force bus ownership after this time */  in pca9541_select_chan()
265 		if (data->select_timeout == SELECT_DELAY_SHORT)  in pca9541_select_chan()
266 			udelay(data->select_timeout);  in pca9541_select_chan()
268 			msleep(data->select_timeout / 1000);  in pca9541_select_chan()
271 	return -ETIMEDOUT;  in pca9541_select_chan()
277 	struct i2c_client *client = data->client;  in pca9541_release_chan()
288 	struct i2c_adapter *adap = client->adapter;  in pca9541_probe()
294 		return -ENODEV;  in pca9541_probe()
306 	muxc = i2c_mux_alloc(adap, &client->dev, 1, sizeof(*data),  in pca9541_probe()
310 		return -ENOMEM;  in pca9541_probe()
313 	data->client = client;  in pca9541_probe()
321 	dev_info(&client->dev, "registered master selector for I2C %s\n",  in pca9541_probe()
322 		 client->name);  in pca9541_probe()
346 MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");