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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: Eric Brower <ebrower@gmail.com>
Acked-by: Dan Smolik <marvin@mydatex.cz>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
This commit is contained in:
Eric Brower 2008-07-14 22:38:31 +02:00 committed by Jean Delvare
parent 8a56ce1033
commit 0573d11b2b
2 changed files with 37 additions and 17 deletions
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48
drivers/i2c/algos/i2c-algo-pcf.c
View File

@ -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

6
include/linux/i2c-algo-pcf.h
View File

@ -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 *);