Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753234AbaLEIdZ (ORCPT ); Fri, 5 Dec 2014 03:33:25 -0500 Received: from mail-ie0-f169.google.com ([209.85.223.169]:50674 "EHLO mail-ie0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753158AbaLEIdW (ORCPT ); Fri, 5 Dec 2014 03:33:22 -0500 MIME-Version: 1.0 In-Reply-To: <1417766884-8383-3-git-send-email-harinik@xilinx.com> References: <1417766884-8383-1-git-send-email-harinik@xilinx.com> <1417766884-8383-3-git-send-email-harinik@xilinx.com> Date: Fri, 5 Dec 2014 14:03:21 +0530 Message-ID: Subject: Re: [PATCH v3 2/2] i2c: cadence: Check for errata condition involving master receive From: rajeev kumar To: Harini Katakam Cc: wsa@the-dreams.de, mark.rutland@arm.com, michal.simek@xilinx.com, soren.brinkmann@xilinx.com, "linux-arm-kernel@lists.infradead.org" , linux-i2c@vger.kernel.org, "linux-kernel@vger.kernel.org" , Harini Katakam , Vishnu Motghare Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 5, 2014 at 1:38 PM, Harini Katakam 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 > Signed-off-by: Vishnu Motghare > --- > > v3: > Add warning in case of unsupported transfer. > Reviewed-by: Rajeev Kumar > 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 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-i2c" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/