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>

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;