[PATCH] i2c-cpm: Fix to takeback i2c bus master-ship after a collision

From: sachin surendran <sachin.surendran@gmail.com>
To: linuxppc-dev@lists.ozlabs.org, jochen@scram.de
Subject: [PATCH] i2c-cpm: Fix to takeback i2c bus master-ship after a collision
Date: Wed, 31 Oct 2012 16:00:26 +1300	[thread overview]
Message-ID: <CABCb4NUJ0uJA5Z9vdgLndvpLrnK=m5xaeiHZxAwHKFU2DroaFw@mail.gmail.com> (raw)

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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 <sachin.surendran@alliedtelesis.co.nz>
---
 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);

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