[PATCH 7/7] can: m_can: workaround for transmit data less than 4 bytes
From: mkl@pengutronix.de (Marc Kleine-Budde)
Date: 2014-11-04 13:28:52
Also in:
linux-can, netdev
On 11/04/2014 02:13 PM, Oliver Hartkopp wrote:
On 04.11.2014 11:33, Marc Kleine-Budde wrote:quoted
On 11/04/2014 10:27 AM, Dong Aisheng wrote:quoted
quoted
+ /* We meet an IC issue that we have to write the full 8At least on the *insert SoC name here*, 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.Yes. Also put the current IP revision (3.0.x) into the comment.
Good idea - also add the SoC's mask revision.
Did inform the Bosch guys from this issue - or is it already in some errata sheet?quoted
quoted
+ * bytes (whatever value for the second word) in Message RAM to + * avoid bit error for transmit data less than 4 bytes at the first + * time. By initializing the first 8 bytes of tx buffer before using + * it can avoid such issue. + */ + 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); }Can you trigger the issue when sending CAN-FD frames with dlc > 8 && dlc < 64?Just a nitpick: DLC can just be 0 .. 15
Correct, I was talking about the length
and the length (struct canfd_frame.len) can be from 0 .. 64 See: http://lxr.free-electrons.com/source/include/uapi/linux/can.h#L83 That's the reason for all these helpers http://lxr.free-electrons.com/source/drivers/net/can/dev.c#L36 that hide the evil "DLC" from userspace now and make 'len' a usable loop variable as we were able to use the former dlc for classic CAN :-)
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