From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756095AbaHVMOz (ORCPT ); Fri, 22 Aug 2014 08:14:55 -0400 Received: from 132.79-246-81.adsl-static.isp.belgacom.be ([81.246.79.132]:42683 "EHLO viper.mind.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754517AbaHVMOy (ORCPT ); Fri, 22 Aug 2014 08:14:54 -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] tps65910: Work around silicon erratum SWCZ010 Date: Fri, 22 Aug 2014 14:14:26 +0200 Message-Id: <1408709666-5927-1-git-send-email-arnout@mind.be> X-Mailer: git-send-email 2.1.0 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. The first access to the tps65910 that we do is when loading the regmap in the probe function. If there has been a glitch during boot and the erratum is triggered, then the regmap loading will fail with -REMOTEIO since the I2C transfer is not ACKed by the tps65910. A simple retry will work around it, because a subsequent I2C start condition is detected properly by the tps65910. 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. --- drivers/mfd/tps65910.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/mfd/tps65910.c b/drivers/mfd/tps65910.c index f243e75..cc1ca33 100644 --- a/drivers/mfd/tps65910.c +++ b/drivers/mfd/tps65910.c @@ -487,8 +487,18 @@ static int tps65910_i2c_probe(struct i2c_client *i2c, tps65910->id = chip_id; tps65910->regmap = devm_regmap_init_i2c(i2c, &tps65910_regmap_config); - if (IS_ERR(tps65910->regmap)) { + if (IS_ERR(tps65910->regmap)) ret = PTR_ERR(tps65910->regmap); + if (ret == -EREMOTEIO) { + dev_warn(&i2c->dev, "regmap initialization failed, possibly due to erratum SWCZ010; trying again\n"); + tps65910->regmap = regmap_init_i2c(i2c, + &tps65910_regmap_config); + if (IS_ERR(tps65910->regmap)) + ret = PTR_ERR(tps65910->regmap); + else + ret = 0; + } + if (ret) { dev_err(&i2c->dev, "regmap initialization failed: %d\n", ret); return ret; } -- 2.1.0