[PATCH 7/7] can: m_can: workaround for transmit data less than 4 bytes
b29396 at freescale.com
Tue Nov 4 18:07:40 PST 2014
On Tue, Nov 04, 2014 at 02:13:30PM +0100, 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.
> Did inform the Bosch guys from this issue - or is it already in some errata sheet?
Good idea, will add it.
I will try if we can talk Bosch guys about this issue.
> >>+ * 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
> 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
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