Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752363AbaL2BQj (ORCPT ); Sun, 28 Dec 2014 20:16:39 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33152 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751861AbaL2BMN (ORCPT ); Sun, 28 Dec 2014 20:12:13 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Uwe Kleine-=?UTF-8?Q?K=C3=B6nig?=" , "Wolfram Sang" , "Hein Tibosch" , "Grygorii Strashko" Date: Mon, 29 Dec 2014 02:11:31 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 06/27] i2c: davinci: generate STP always when NACK is received In-Reply-To: X-SA-Exim-Connect-IP: 46.189.28.191 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.66-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Grygorii Strashko commit 9ea359f7314132cbcb5a502d2d8ef095be1f45e4 upstream. According to I2C specification the NACK should be handled as follows: "When SDA remains HIGH during this ninth clock pulse, this is defined as the Not Acknowledge signal. The master can then generate either a STOP condition to abort the transfer, or a repeated START condition to start a new transfer." [I2C spec Rev. 6, 3.1.6: http://www.nxp.com/documents/user_manual/UM10204.pdf] Currently the Davinci i2c driver interrupts the transfer on receipt of a NACK but fails to send a STOP in some situations and so makes the bus stuck until next I2C IP reset (idle/enable). For example, the issue will happen during SMBus read transfer which consists from two i2c messages write command/address and read data: S Slave Address Wr A Command Code A Sr Slave Address Rd A D1..Dn A P <--- write -----------------------> <--- read ---------------------> The I2C client device will send NACK if it can't recognize "Command Code" and it's expected from I2C master to generate STP in this case. But now, Davinci i2C driver will just exit with -EREMOTEIO and STP will not be generated. Hence, fix it by generating Stop condition (STP) always when NACK is received. This patch fixes Davinci I2C in the same way it was done for OMAP I2C commit cda2109a26eb ("i2c: omap: query STP always when NACK is received"). Reviewed-by: Uwe Kleine-König Reported-by: Hein Tibosch Signed-off-by: Grygorii Strashko Signed-off-by: Wolfram Sang Signed-off-by: Ben Hutchings --- drivers/i2c/busses/i2c-davinci.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) --- a/drivers/i2c/busses/i2c-davinci.c +++ b/drivers/i2c/busses/i2c-davinci.c @@ -416,11 +416,9 @@ i2c_davinci_xfer_msg(struct i2c_adapter if (dev->cmd_err & DAVINCI_I2C_STR_NACK) { if (msg->flags & I2C_M_IGNORE_NAK) return msg->len; - if (stop) { - w = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG); - w |= DAVINCI_I2C_MDR_STP; - davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, w); - } + w = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG); + w |= DAVINCI_I2C_MDR_STP; + davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, w); return -EREMOTEIO; } return -EIO; -- 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/