summaryrefslogtreecommitdiff
path: root/drivers/i2c
diff options
context:
space:
mode:
authorHarini Katakam <harinik@xilinx.com>2015-01-14 00:04:59 +0530
committerWolfram Sang <wsa@the-dreams.de>2015-01-14 11:36:58 +0100
commit8a86c3aee0cfec09b35159da9d925157f3e4f2cc (patch)
tree5c9612020efa6cb0d27c744291a0135451013d1d /drivers/i2c
parentef2829144dc995d8263dbec3b057a29541e789b4 (diff)
i2c: cadence: Check for errata condition involving master receive
Cadence I2C controller has the following bugs: - completion indication is not given to the driver at the end of a read/receive transfer with HOLD bit set. - Invalid read transaction are generated on the bus when HW timeout condition occurs with HOLD bit set. As a result of the above, if a set of messages to be transferred with repeated start includes any message following a read message, completion is never indicated and timeout occurs. Hence a check is implemented to return -EOPNOTSUPP for such sequences. Signed-off-by: Harini Katakam <harinik@xilinx.com> Signed-off-by: Vishnu Motghare <vishnum@xilinx.com> [wsa: fixed some whitespaces] Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/busses/i2c-cadence.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
index 871cb58aaa06..7d7a14cdadfb 100644
--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -545,6 +545,20 @@ static int cdns_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
* processed with a repeated start.
*/
if (num > 1) {
+ /*
+ * This controller does not give completion interrupt after a
+ * master receive message if HOLD bit is set (repeated start),
+ * resulting in SW timeout. Hence, if a receive message is
+ * followed by any other message, an error is returned
+ * indicating that this sequence is not supported.
+ */
+ for (count = 0; count < num - 1; count++) {
+ if (msgs[count].flags & I2C_M_RD) {
+ dev_warn(adap->dev.parent,
+ "Can't do repeated start after a receive message\n");
+ return -EOPNOTSUPP;
+ }
+ }
id->bus_hold_flag = 1;
reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
reg |= CDNS_I2C_CR_HOLD;