From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dong Aisheng 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> References: <1415174326-6623-1-git-send-email-b29396@freescale.com> Mime-Version: 1.0 Content-Type: text/plain Cc: , , , , , , To: Return-path: In-Reply-To: <1415174326-6623-1-git-send-email-b29396@freescale.com> Sender: linux-can-owner@vger.kernel.org List-Id: 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); } -- 1.9.1