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Commit 0573d11b authored by Eric Brower's avatar Eric Brower Committed by Jean Delvare
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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: default avatarEric Brower <ebrower@gmail.com>
Acked-by: default avatarDan Smolik <marvin@mydatex.cz>
Signed-off-by: default avatarJean Delvare <khali@linux-fr.org>
parent 8a56ce10

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

+31 −17
Original line number Diff line number Diff line
@@ -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

+6 −0
Original line number Diff line number Diff line
@@ -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 *);