From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753243Ab0EJPax (ORCPT ); Mon, 10 May 2010 11:30:53 -0400 Received: from smtp.gentoo.org ([140.211.166.183]:49639 "EHLO smtp.gentoo.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752782Ab0EJPav (ORCPT ); Mon, 10 May 2010 11:30:51 -0400 From: Mike Frysinger To: linux-i2c@vger.kernel.org, Ben Dooks Cc: uclinux-dist-devel@blackfin.uclinux.org, linux-kernel@vger.kernel.org, Andrew Morton , Michael Hennerich Subject: [PATCH v2] i2c-bfin-twi: handle faulty slave devices better Date: Mon, 10 May 2010 11:33:44 -0400 Message-Id: <1273505624-30920-1-git-send-email-vapier@gentoo.org> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1273403087-3326-1-git-send-email-vapier@gentoo.org> References: <1273403087-3326-1-git-send-email-vapier@gentoo.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michael Hennerich Faulty slave devices might drive SDA low after a transfer finishes. So, when this scenario is detected, have the master generate up to 9 extra clocks until the SDA is properly released. Signed-off-by: Michael Hennerich Signed-off-by: Mike Frysinger --- v2 - fix typo in comment pointed out by Ben - use 9 clocks rather than 8 to cover a possible NACK pointed out by Michael drivers/i2c/busses/i2c-bfin-twi.c | 22 ++++++++++++++++++++++ 1 files changed, 22 insertions(+), 0 deletions(-) diff --git a/drivers/i2c/busses/i2c-bfin-twi.c b/drivers/i2c/busses/i2c-bfin-twi.c index fb26e5c..1ee9d5a 100644 --- a/drivers/i2c/busses/i2c-bfin-twi.c +++ b/drivers/i2c/busses/i2c-bfin-twi.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include @@ -159,6 +160,27 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface, if (mast_stat & BUFWRERR) dev_dbg(&iface->adap.dev, "Buffer Write Error\n"); + /* Faulty slave devices, may drive SDA low after a transfer + * finishes. To release the bus this code generates up to 9 + * extra clocks until SDA is released. + */ + + if (read_MASTER_STAT(iface) & SDASEN) { + int cnt = 9; + do { + write_MASTER_CTL(iface, SCLOVR); + udelay(6); + write_MASTER_CTL(iface, 0); + udelay(6); + } while ((read_MASTER_STAT(iface) & SDASEN) && cnt--); + + write_MASTER_CTL(iface, SDAOVR | SCLOVR); + udelay(6); + write_MASTER_CTL(iface, SDAOVR); + udelay(6); + write_MASTER_CTL(iface, 0); + } + /* If it is a quick transfer, only address without data, * not an err, return 1. */ -- 1.7.1