Currently, the i2c-algo-pca driver does nothing if the chip enters state 0x30 (Data byte in I2CDAT has been transmitted; NOT ACK has been received). Thus, the i2c bus connected to the controller gets stuck afterwards.
I have seen this kind of error on a custom board in certain load situations most probably caused by interference or noise. A possible reaction is to let the controller generate a STOP condition. This is documented in the controller data sheet and the same is done for other NACK states as well. Further, state 0x38 isn't handled completely, either. Try to do another START in this case like the manual says. As this couldn't be tested, I've added a comment to try to reset the chip if the START doesn't help as suggested by Wolfram Sang. Signed-off-by: Enrik Berkhan <[email protected]> --- drivers/i2c/algos/i2c-algo-pca.c | 7 +++++++ 1 file changed, 7 insertions(+) Index: drivers/i2c/algos/i2c-algo-pca.c =================================================================== --- drivers/i2c/algos/i2c-algo-pca.c.orig 2009-04-07 11:23:08.000000000 +0200 +++ drivers/i2c/algos/i2c-algo-pca.c 2009-04-09 11:10:11.000000000 +0200 @@ -270,10 +270,17 @@ static int pca_xfer(struct i2c_adapter * case 0x30: /* Data byte in I2CDAT has been transmitted; NOT ACK has been received */ DEB2("NOT ACK received after data byte\n"); + pca_stop(adap); goto out; case 0x38: /* Arbitration lost during SLA+W, SLA+R or data bytes */ DEB2("Arbitration lost\n"); + /* + * The manual says to send another start + * condition in this case. If this won't be + * sufficient, try pca_reset() instead. + */ + pca_start(adap); goto out; case 0x58: /* Data byte has been received; NOT ACK has been returned */ -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
