i2c-algo-pcf: Multi-master lost-arbitration improvement

Improve lost-arbitration handling of PCF8584.  This is necessary for
support of a currently out-of-kernel driver for Sun Microsystems E250
environmental management; perhaps others.

Signed-off-by: Eric Brower <ebrower@gmail.com>
Acked-by: Dan Smolik <marvin@mydatex.cz>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

drivers/i2c/algos/i2c-algo-pcf.c

@@ -78,6 +78,36 @@ static void i2c_stop(struct i2c_algo_pcf_data *adap)
 	set_pcf(adap, 1, I2C_PCF_STOP);
 }
 
+static void handle_lab(struct i2c_algo_pcf_data *adap, const int *status)
+{
+	DEB2(printk(KERN_INFO
+		"i2c-algo-pcf.o: lost arbitration (CSR 0x%02x)\n",
+		 *status));
+
+	/* Cleanup from LAB -- reset and enable ESO.
+	 * This resets the PCF8584; since we've lost the bus, no
+	 * further attempts should be made by callers to clean up
+	 * (no i2c_stop() etc.)
+	 */
+	set_pcf(adap, 1, I2C_PCF_PIN);
+	set_pcf(adap, 1, I2C_PCF_ESO);
+
+	/* We pause for a time period sufficient for any running
+	 * I2C transaction to complete -- the arbitration logic won't
+	 * work properly until the next START is seen.
+	 * It is assumed the bus driver or client has set a proper value.
+	 *
+	 * REVISIT: should probably use msleep instead of mdelay if we
+	 * know we can sleep.
+	 */
+	if (adap->lab_mdelay)
+		mdelay(adap->lab_mdelay);
+
+	DEB2(printk(KERN_INFO
+		"i2c-algo-pcf.o: reset LAB condition (CSR 0x%02x)\n",
+		get_pcf(adap, 1)));
+}
+
 static int wait_for_bb(struct i2c_algo_pcf_data *adap) {
 
 	int timeout = DEF_TIMEOUT;
@@ -109,23 +139,7 @@ static int wait_for_pin(struct i2c_algo_pcf_data *adap, int *status) {
 		*status = get_pcf(adap, 1);
 	}
 	if (*status & I2C_PCF_LAB) {
-		DEB2(printk(KERN_INFO 
-			"i2c-algo-pcf.o: lost arbitration (CSR 0x%02x)\n",
-			 *status));
-		/* Cleanup from LAB-- reset and enable ESO.
-		 * This resets the PCF8584; since we've lost the bus, no
-		 * further attempts should be made by callers to clean up 
-		 * (no i2c_stop() etc.)
-		 */
-		set_pcf(adap, 1, I2C_PCF_PIN);
-		set_pcf(adap, 1, I2C_PCF_ESO);
-		/* TODO: we should pause for a time period sufficient for any
-		 * running I2C transaction to complete-- the arbitration
-		 * logic won't work properly until the next START is seen.
-		 */
-		DEB2(printk(KERN_INFO 
-			"i2c-algo-pcf.o: reset LAB condition (CSR 0x%02x)\n", 
-			get_pcf(adap,1)));
+		handle_lab(adap, status);
 		return(-EINTR);
 	}
 #endif

include/linux/i2c-algo-pcf.h

@@ -36,6 +36,12 @@ struct i2c_algo_pcf_data {
 	/* local settings */
 	int udelay;
 	int timeout;
+
+	/* Multi-master lost arbitration back-off delay (msecs)
+	 * This should be set by the bus adapter or knowledgable client
+	 * if bus is multi-mastered, else zero
+	 */
+	unsigned long lab_mdelay;
 };
 
 int i2c_pcf_add_bus(struct i2c_adapter *);