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author | Harini Katakam <harinik@xilinx.com> | 2015-01-13 19:34:59 +0100 |
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committer | Wolfram Sang <wsa@the-dreams.de> | 2015-01-14 11:36:58 +0100 |
commit | 8a86c3aee0cfec09b35159da9d925157f3e4f2cc (patch) | |
tree | 5c9612020efa6cb0d27c744291a0135451013d1d /drivers/i2c | |
parent | dt-bindings: use isil prefix for Intersil in I2C trivial-devices.txt (diff) | |
download | linux-8a86c3aee0cfec09b35159da9d925157f3e4f2cc.tar.xz linux-8a86c3aee0cfec09b35159da9d925157f3e4f2cc.zip |
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.c | 14 |
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; |