From mboxrd@z Thu Jan 1 00:00:00 1970 From: harinik@xilinx.com (Harini Katakam) Date: Wed, 3 Dec 2014 18:05:26 +0530 Subject: [PATCH v2 3/3] i2c: cadence: Check for errata condition involving master receive In-Reply-To: <1417610126-7957-1-git-send-email-harinik@xilinx.com> References: <1417610126-7957-1-git-send-email-harinik@xilinx.com> Message-ID: <1417610126-7957-4-git-send-email-harinik@xilinx.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 Signed-off-by: Vishnu Motghare --- v2: Dont defeteature repeated start. Just check for unsupported conditions in the driver and return error. --- drivers/i2c/busses/i2c-cadence.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c index 67077c2..f5437e2 100644 --- a/drivers/i2c/busses/i2c-cadence.c +++ b/drivers/i2c/busses/i2c-cadence.c @@ -522,6 +522,17 @@ 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) + return -EOPNOTSUPP; + } id->bus_hold_flag = 1; reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET); reg |= CDNS_I2C_CR_HOLD; -- 1.7.9.5