Messages in this thread Patch in this message | | | From | Harini Katakam <> | Subject | [PATCH v3 2/2] i2c: cadence: Check for errata condition involving master receive | Date | Fri, 5 Dec 2014 13:38:04 +0530 |
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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 transfer following a read transfer, 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> ---
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 | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c index 5f5d4fa..3ea3b7a 100644 --- a/drivers/i2c/busses/i2c-cadence.c +++ b/drivers/i2c/busses/i2c-cadence.c @@ -541,6 +541,21 @@ 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 transfer if HOLD bit is set (repeated start), + * resulting in SW timeout. Hence, if a receive transfer is + * followed by any other transfer, 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, + "No support for repeated start when\t"); + dev_warn(adap->dev.parent, + "receive is followed by a transfer\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
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