From patchwork Sun Nov 25 22:20:01 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [1/1] i2c-cpm: Fix to takeback i2c bus master-ship after a collision From: sachin surendran X-Patchwork-Id: 201596 Message-Id: <1353882001-30744-1-git-send-email-sachin.surendran@gmail.com> To: galak@kernel.crashing.org, jochen@scram.de Cc: Sachin Surendran , sachin.surendran@gmail.com, linuxppc-dev@lists.ozlabs.org Date: Mon, 26 Nov 2012 11:20:01 +1300 From: Sachin Surendran In case of collision on i2c bus the controller which lost bus mastership stays as a slave for all subsequent transfers. This results in the i2c controller never writing to the bus for future transactions, resulting in i2c transfer timeouts. This fix checks for a collision on last I2C transaction and sets the I2COM_MASTER bit for the new transaction. Signed-off-by: Sachin Surendran --- drivers/i2c/busses/i2c-cpm.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/i2c/busses/i2c-cpm.c b/drivers/i2c/busses/i2c-cpm.c index c1e1096..bb94c6d 100644 --- a/drivers/i2c/busses/i2c-cpm.c +++ b/drivers/i2c/busses/i2c-cpm.c @@ -338,6 +338,14 @@ static int cpm_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) tptr = 0; rptr = 0; + /* + * If there was a collision in the last i2c transaction, + * Set I2COM_MASTER as it was cleared during collision. + */ + if (in_be16(&tbdf->cbd_sc) & BD_SC_CL) { + out_8(&cpm->i2c_reg->i2com, I2COM_MASTER); + } + while (tptr < num) { pmsg = &msgs[tptr]; dev_dbg(&adap->dev, "R: %d T: %d\n", rptr, tptr);