Hello Oliver,

On 11/28/20 6:23 PM, Oliver Hartkopp wrote:

On 27.11.20 12:09, Jeroen Hofstee wrote:

quoted

Hi,

On 11/27/20 11:30 AM, Marc Kleine-Budde wrote:

quoted

On 11/27/20 10:59 AM, Jeroen Hofstee wrote:

quoted

Losing arbitration is normal in a CAN-bus network, it means that a
higher priority frame is being send and the pending message will be
retried later. Hence most driver only increment arbitration_lost, but
the sja1000 and sun4i driver also incremeant tx_error, causing errors
to be reported on a normal functioning CAN-bus. So stop counting them
as errors.

Sounds plausible.

quoted

For completeness, the Kvaser USB hybra also increments the tx_error
on arbitration lose, but it does so in single shot. Since in that
case the message is not retried, that behaviour is kept.

You mean only in one shot mode?

Yes, well at least the function is called 
kvaser_usb_hydra_one_shot_fail.

quoted

  What about one shot mode on the sja1000 cores?

That is a good question. I guess it will be counted as error by:

         if (isrc & IRQ_TI) {
             /* transmission buffer released */
             if (priv->can.ctrlmode & CAN_CTRLMODE_ONE_SHOT &&
                 !(status & SR_TCS)) {
                 stats->tx_errors++;
                 can_free_echo_skb(dev, 0);
             } else {
                 /* transmission complete */
                 stats->tx_bytes +=
                     priv->read_reg(priv, SJA1000_FI) & 0xf;
                 stats->tx_packets++;
                 can_get_echo_skb(dev, 0);
             }
             netif_wake_queue(dev);
             can_led_event(dev, CAN_LED_EVENT_TX);
         }

 From the datasheet, Transmit Interrupt:

"set; this bit is set whenever the transmit bufferstatus
changes from ‘0-to-1’ (released) and the TIE bit is set
within the interrupt enable register".

I cannot test it though, since I don't have a sja1000.

I have a PCAN-ExpressCard 34 here, which should make it in a test 
setup as it acts as a PCI attached SJA1000.

Will take a look at that arbitration lost behaviour on Monday. A 
really interesting detail!

Thanks, appreciated. I would be surprised if this path is not taken though.

With kind regards,

Jeroen