From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751016AbaHVTGj (ORCPT ); Fri, 22 Aug 2014 15:06:39 -0400 Received: from 132.79-246-81.adsl-static.isp.belgacom.be ([81.246.79.132]:44324 "EHLO viper.mind.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750879AbaHVTGi (ORCPT ); Fri, 22 Aug 2014 15:06:38 -0400 From: "Arnout Vandecappelle (Essensium/Mind)" To: Samuel Ortiz , Lee Jones , Mark Brown , linux-kernel@vger.kernel.org Cc: Laxman Dewangan , David Brown , "Arnout Vandecappelle (Essensium/Mind)" Subject: [PATCH v2] tps65910: Work around silicon erratum SWCZ010 Date: Fri, 22 Aug 2014 17:30:56 +0200 Message-Id: <1408721456-8101-1-git-send-email-arnout@mind.be> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1408709666-5927-1-git-send-email-arnout@mind.be> References: <1408709666-5927-1-git-send-email-arnout@mind.be> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>From http://www.ti.com/lit/pdf/SWCZ010 : Glitch on SDA-SCL not managed correctly by the I2C IP Impact: The standard specifies that the I2C transfer should restart on a start event in all cases. The current design does not support two consecutive Start conditions. This can cause the first real access after such a glitch to be corrupted. Description: An unexpected glitch on SDA and SCL can generate a wrong start event. In the current design, the SCL line must toggle two times to detect a new start event and completely restart the I2C access; hence the real start event is not detected in the case of a single SCL toggle. Workaround: Repeat I2C access. A simpler workaround is to make a dummy transfer just before the first access to the tps65910 chip. This can be done unconditionally. Signed-off-by: Arnout Vandecappelle (Essensium/Mind) --- This patch is based on v3.17-rc1. Build-tested with omap2plus_defconfig. Runtime tested based on v3.4.97 with a custom config. v2: use dummy transfer instead of retrying (Laxman Dewangan) --- drivers/mfd/tps65910.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/mfd/tps65910.c b/drivers/mfd/tps65910.c index f243e75..7612d89 100644 --- a/drivers/mfd/tps65910.c +++ b/drivers/mfd/tps65910.c @@ -486,6 +486,11 @@ static int tps65910_i2c_probe(struct i2c_client *i2c, tps65910->i2c_client = i2c; tps65910->id = chip_id; + /* Work around silicon erratum SWCZ010: the tps65910 may miss the + * first I2C transfer. So issue a dummy transfer before the first + * real transfer. + */ + i2c_master_send(i2c, "", 1); tps65910->regmap = devm_regmap_init_i2c(i2c, &tps65910_regmap_config); if (IS_ERR(tps65910->regmap)) { ret = PTR_ERR(tps65910->regmap); -- 2.1.0