From 8a86c3aee0cfec09b35159da9d925157f3e4f2cc Mon Sep 17 00:00:00 2001 From: Harini Katakam Date: Wed, 14 Jan 2015 00:04:59 +0530 Subject: [PATCH] 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 Signed-off-by: Vishnu Motghare [wsa: fixed some whitespaces] Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-cadence.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) 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;