On Fri, Dec 5, 2014 at 1:38 PM, Harini Katakam <harinik@xxxxxxxxxx> wrote:
> 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@xxxxxxxxxx>
> Signed-off-by: Vishnu Motghare <vishnum@xxxxxxxxxx>
> ---
>
> v3:
> Add warning in case of unsupported transfer.
>
Reviewed-by: Rajeev Kumar <rajeevkumar.linux@xxxxxxxxx>
> 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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