From patchwork Wed Nov 5 07:58:44 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dong Aisheng X-Patchwork-Id: 406909 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 5D38B140098 for ; Wed, 5 Nov 2014 20:05:46 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753991AbaKEJFl (ORCPT ); Wed, 5 Nov 2014 04:05:41 -0500 Received: from mail-by2on0103.outbound.protection.outlook.com ([207.46.100.103]:16544 "EHLO na01-by2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753507AbaKEJFW (ORCPT ); Wed, 5 Nov 2014 04:05:22 -0500 Received: from BN3PR0301CA0007.namprd03.prod.outlook.com (25.160.180.145) by BLUPR03MB327.namprd03.prod.outlook.com (10.141.48.18) with Microsoft SMTP Server (TLS) id 15.1.11.9; Wed, 5 Nov 2014 09:05:18 +0000 Received: from BN1AFFO11FD035.protection.gbl (2a01:111:f400:7c10::181) by BN3PR0301CA0007.outlook.office365.com (2a01:111:e400:4000::17) with Microsoft SMTP Server (TLS) id 15.1.11.14 via Frontend Transport; Wed, 5 Nov 2014 09:05:18 +0000 Received: from tx30smr01.am.freescale.net (192.88.168.50) by BN1AFFO11FD035.mail.protection.outlook.com (10.58.52.159) with Microsoft SMTP Server (TLS) id 15.1.6.13 via Frontend Transport; Wed, 5 Nov 2014 09:05:18 +0000 Received: from shlinux2.ap.freescale.net (shlinux2.ap.freescale.net [10.192.224.44]) by tx30smr01.am.freescale.net (8.14.3/8.14.0) with ESMTP id sA5957Qs031871; Wed, 5 Nov 2014 02:05:15 -0700 From: Dong Aisheng To: CC: , , , , , , Subject: [PATCH V2 2/4] can: m_can: workaround for transmit data less than 4 bytes Date: Wed, 5 Nov 2014 15:58:44 +0800 Message-ID: <1415174326-6623-2-git-send-email-b29396@freescale.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1415174326-6623-1-git-send-email-b29396@freescale.com> References: <1415174326-6623-1-git-send-email-b29396@freescale.com> X-EOPAttributedMessage: 0 X-Forefront-Antispam-Report: CIP:192.88.168.50; CTRY:US; IPV:CAL; IPV:NLI; EFV:NLI; SFV:NSPM; SFS:(10019020)(6009001)(199003)(189002)(54534003)(76176999)(50986999)(229853001)(105606002)(92566001)(31966008)(102836001)(21056001)(64706001)(26826002)(99396003)(47776003)(106466001)(97736003)(95666004)(2351001)(4396001)(20776003)(50226001)(36756003)(107046002)(62966003)(110136001)(46102003)(93916002)(50466002)(88136002)(87936001)(87286001)(19580405001)(48376002)(92726001)(33646002)(44976005)(104166001)(120916001)(77156002)(104016003)(84676001)(6806004)(68736004)(19580395003)(89996001)(42262002); DIR:OUT; SFP:1102; SCL:1; SRVR:BLUPR03MB327; H:tx30smr01.am.freescale.net; FPR:; MLV:ovrnspm; PTR:InfoDomainNonexistent; A:1; MX:1; LANG:en; MIME-Version: 1.0 X-Microsoft-Antispam: UriScan:; X-Microsoft-Antispam: BCL:0;PCL:0;RULEID:;SRVR:BLUPR03MB327; X-Exchange-Antispam-Report-Test: UriScan:; X-Forefront-PRVS: 0386B406AA Received-SPF: Fail (protection.outlook.com: domain of freescale.com does not designate 192.88.168.50 as permitted sender) receiver=protection.outlook.com; client-ip=192.88.168.50; helo=tx30smr01.am.freescale.net; Authentication-Results: spf=fail (sender IP is 192.88.168.50) smtp.mailfrom=Aisheng.Dong@freescale.com; X-OriginatorOrg: freescale.com Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org At least on the i.MX6SX with M_CAN IP version 3.0.x, an issue with the Message RAM was discovered. Sending CAN frames with dlc less than 4 bytes will lead to bit errors, when the first 8 bytes of the Message RAM have not been initialized (i.e. written to). To work around this issue, the first 8 bytes are initialized in open() function. Without the workaround, we can easily see the following errors: root@imx6qdlsolo:~# ip link set can0 up type can bitrate 1000000 [ 66.882520] IPv6: ADDRCONF(NETDEV_CHANGE): can0: link becomes ready root@imx6qdlsolo:~# cansend can0 123#112233 [ 66.935640] m_can 20e8000.can can0: Bit Error Uncorrected Signed-off-by: Dong Aisheng --- ChangeLog since v1: * initialize the first 8 bytes of Tx Buffer of Message RAM in open() to workaround the issue --- drivers/net/can/m_can/m_can.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c index 664fe30..f47c200 100644 --- a/drivers/net/can/m_can/m_can.c +++ b/drivers/net/can/m_can/m_can.c @@ -902,6 +902,15 @@ static void m_can_chip_config(struct net_device *dev) /* set bittiming params */ m_can_set_bittiming(dev); + /* At least on the i.MX6SX with M_CAN IP version 3.0.x, an issue with + * the Message RAM was discovered. Sending CAN frames with dlc less + * than 4 bytes will lead to bit errors, when the first 8 bytes of + * the Message RAM have not been initialized (i.e. written to). + * To work around this issue, the first 8 bytes are initialized here. + */ + m_can_fifo_write(priv, 0, M_CAN_FIFO_DATA(0), 0x0); + m_can_fifo_write(priv, 0, M_CAN_FIFO_DATA(1), 0x0); + m_can_config_endisable(priv, false); }