From mboxrd@z Thu Jan 1 00:00:00 1970 From: wsa@the-dreams.de (Wolfram Sang) Date: Tue, 13 Jan 2015 12:35:38 +0100 Subject: [PATCH v5 2/2] i2c: cadence: Check for errata condition involving master receive In-Reply-To: <1418357907-4215-3-git-send-email-harinik@xilinx.com> References: <1418357907-4215-1-git-send-email-harinik@xilinx.com> <1418357907-4215-3-git-send-email-harinik@xilinx.com> Message-ID: <20150113113538.GB7660@katana> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org > @@ -541,6 +541,18 @@ 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 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; Have you ever tested this code? There is a huge bug in it :( Also, in the comment, use "message" instead of "transfer". One transfer consists of multiple messages. Maybe the warning can be simplified, too: "can't do repeated start after read messages". -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: