Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935196AbbDIKEx (ORCPT ); Thu, 9 Apr 2015 06:04:53 -0400 Received: from mail.kernel.org ([198.145.29.136]:40967 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932889AbbDIIvK (ORCPT ); Thu, 9 Apr 2015 04:51:10 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Grygorii Strashko , Wolfram Sang , Zefan Li Subject: [PATCH 3.4 028/176] i2c: davinci: generate STP always when NACK is received Date: Thu, 9 Apr 2015 16:44:36 +0800 Message-Id: <1428569224-23820-28-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1428569028-23762-1-git-send-email-lizf@kernel.org> References: <1428569028-23762-1-git-send-email-lizf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2871 Lines: 71 From: Grygorii Strashko 3.4.107-rc1 review patch. If anyone has any objections, please let me know. ------------------ 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: Zefan Li --- drivers/i2c/busses/i2c-davinci.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c index 79b4bcb..1837fe6 100644 --- 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 *adap, struct i2c_msg *msg, int stop) 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; -- 1.9.1 -- 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/