From patchwork Wed Sep 12 06:42:11 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ludovic Desroches X-Patchwork-Id: 1441141 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork1.kernel.org Received: from merlin.infradead.org (unknown [205.233.59.134]) by patchwork1.kernel.org (Postfix) with ESMTP id E54C53FC71 for ; Wed, 12 Sep 2012 06:52:00 +0000 (UTC) Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1TBgfB-000538-8j; Wed, 12 Sep 2012 06:43:05 +0000 Received: from eusmtp01.atmel.com ([212.144.249.242]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1TBgey-0004za-NY for linux-arm-kernel@lists.infradead.org; Wed, 12 Sep 2012 06:42:53 +0000 Received: from ibiza.corp.atmel.com (10.161.101.13) by eusmtp01.atmel.com (10.161.101.30) with Microsoft SMTP Server id 14.2.318.1; Wed, 12 Sep 2012 08:44:30 +0200 From: To: , , Subject: [PATCH v3 2/8] i2c: at91: add warning about transmission issues for some devices Date: Wed, 12 Sep 2012 08:42:11 +0200 Message-ID: <1347432137-25058-3-git-send-email-ludovic.desroches@atmel.com> X-Mailer: git-send-email 1.7.11.3 In-Reply-To: <1347432137-25058-1-git-send-email-ludovic.desroches@atmel.com> References: <1347432137-25058-1-git-send-email-ludovic.desroches@atmel.com> MIME-Version: 1.0 X-Spam-Note: CRM114 invocation failed X-Spam-Score: -2.3 (--) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-2.3 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 SPF_PASS SPF: sender matches SPF record -0.3 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Cc: plagnioj@jcrosoft.com, n.voss@weinmann.de, nicolas.ferre@atmel.com, w.sang@pengutronix.de, Ludovic Desroches X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: Ludovic Desroches Some devices don't have clock streching in transmission mode. It can lead to premature stop sendings if the latency to write data in the transmission register is too long. In this case, prefer the i2c-gpio driver. Signed-off-by: Ludovic Desroches Acked-by: Nikolaus Voss Acked-by: Nicolas Ferre --- drivers/i2c/busses/Kconfig | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig index d9c4918..da77c37 100644 --- a/drivers/i2c/busses/Kconfig +++ b/drivers/i2c/busses/Kconfig @@ -300,6 +300,12 @@ config I2C_AT91 to support combined I2C messages. Use the i2c-gpio driver unless your system can cope with this limitation. + Caution! at91rm9200, at91sam9261, at91sam9260, at91sam9263 devices + don't have clock stretching in transmission mode. For that reason, + you can encounter underrun issues causing premature stop sendings if + the latency to fill the transmission register is too long. If you + are facing this situation, use the i2c-gpio driver. + config I2C_AU1550 tristate "Au1550/Au1200/Au1300 SMBus interface" depends on MIPS_ALCHEMY