From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dong Aisheng Subject: [PATCH V3 3/3] can: m_can: workaround for transmit data less than 4 bytes Date: Wed, 5 Nov 2014 21:16:33 +0800 Message-ID: <1415193393-30023-3-git-send-email-b29396@freescale.com> References: <1415193393-30023-1-git-send-email-b29396@freescale.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <1415193393-30023-1-git-send-email-b29396@freescale.com> Sender: netdev-owner@vger.kernel.org To: linux-can@vger.kernel.org Cc: mkl@pengutronix.de, wg@grandegger.com, varkabhadram@gmail.com, netdev@vger.kernel.org, socketcan@hartkopp.net, b29396@freescale.com, linux-arm-kernel@lists.infradead.org List-Id: linux-can.vger.kernel.org At least on the i.MX6SX TO1.2 with M_CAN IP version 3.0.1, 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 v2->v3: * add i.MX chip version in issue in commit message v1->v2: * 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 | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c index eee1533..567cd27 100644 --- a/drivers/net/can/m_can/m_can.c +++ b/drivers/net/can/m_can/m_can.c @@ -905,6 +905,16 @@ static void m_can_chip_config(struct net_device *dev) /* set bittiming params */ m_can_set_bittiming(dev); + /* At least on the i.MX6SX TO1.2 with M_CAN IP version 3.0.1, + * (CREL = 30130506) 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); } -- 1.9.1