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@xxxxxxxxxx>
Signed-off-by: Vishnu Motghare <vishnum@xxxxxxxxxx>
---
v6:
- Correct if condition - add braces to include both statements.
- Modify comments and warning message.
v5:
Make warning grepable in driver.
v4:
Use single dev_warn and make message grep-able.
v3:
Add warning in case of unsupported transfer.
v2:
Dont defeteature repeated start. Just check for unsupported conditions in the
driver and return error.
---
drivers/i2c/busses/i2c-cadence.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
index 5f5d4fa..c7be4fb 100644
--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -541,6 +541,19 @@ 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;
--
1.7.9.5
--
To unsubscribe from this list: send the line "unsubscribe linux-i2c" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
