Patchwork [1/1] i2c-cpm: Fix to takeback i2c bus master-ship after a collision

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Submitter sachin surendran
Date Nov. 25, 2012, 10:20 p.m.
Message ID <1353882001-30744-1-git-send-email-sachin.surendran@gmail.com>
Download mbox | patch
Permalink /patch/201596/
State Accepted, archived
Commit a16d8aa4726a944ffc1616689ae34ff6a902faba
Delegated to: Scott Wood
Headers show

Comments

sachin surendran - Nov. 25, 2012, 10:20 p.m.
From: Sachin Surendran <sachin.surendran@alliedtelesis.co.nz>

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(+)

Patch

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);