[PATCH 7/7] can: m_can: workaround for transmit data less than 4 bytes
mkl at pengutronix.de
Tue Nov 4 05:28:52 PST 2014
On 11/04/2014 02:13 PM, Oliver Hartkopp wrote:
> On 04.11.2014 11:33, Marc Kleine-Budde wrote:
>> On 11/04/2014 10:27 AM, Dong Aisheng wrote:
>>> + /* We meet an IC issue that we have to write the full 8
>> At 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?
>>> + * bytes (whatever value for the second word) in Message RAM to
>>> + * avoid bit error for transmit data less than 4 bytes at the
>>> + * 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
> That's the reason for all these helpers
> 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 :-)
Pengutronix e.K. | Marc Kleine-Budde |
Industrial Linux Solutions | Phone: +49-231-2826-924 |
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