Re: [PATCH v5 2/5] can: kvaser_usb: Consolidate and unify state change handling

Ahmed S. Darwish
2015-01-21T15:36:52Z

On Wed, Jan 21, 2015 at 03:00:15PM +0000, Andri Yngvason wrote:
> Quoting Ahmed S. Darwish (2015-01-21 14:43:23)
> > Hi!

...

> > <-- Unplug the cable -->
> >
> > (000.009106) can0 20000080 [8] 00 00 00 00 00 00 08 00 ERRORFRAME
> > bus-error
> > error-counter-tx-rx{{8}{0}}
> > (000.001872) can0 20000080 [8] 00 00 00 00 00 00 10 00 ERRORFRAME
> > bus-error
> > error-counter-tx-rx{{16}{0}}
> [...]
> > error-counter-tx-rx{{80}{0}}
> > (000.001910) can0 20000080 [8] 00 00 00 00 00 00 58 00 ERRORFRAME
> > bus-error
> > error-counter-tx-rx{{88}{0}}
> > (000.001753) can0 20000084 [8] 00 08 00 00 00 00 60 00 ERRORFRAME
> > controller-problem{tx-error-warning}
> Good.
> > bus-error
> > error-counter-tx-rx{{96}{0}}

Nice.

> > (000.001720) can0 20000080 [8] 00 00 00 00 00 00 68 00 ERRORFRAME
> > bus-error
> > error-counter-tx-rx{{104}{0}}
> > (000.001876) can0 20000080 [8] 00 00 00 00 00 00 70 00 ERRORFRAME
> > bus-error
> > error-counter-tx-rx{{112}{0}}
> > (000.001749) can0 20000080 [8] 00 00 00 00 00 00 78 00 ERRORFRAME
> > bus-error
> > error-counter-tx-rx{{120}{0}}
> > (000.001771) can0 20000084 [8] 00 20 00 00 00 00 80 00 ERRORFRAME
> > controller-problem{tx-error-passive}
> Also good.
> > bus-error
> > error-counter-tx-rx{{128}{0}}

Also nice :-)

> > (000.001868) can0 20000080 [8] 00 00 00 00 00 00 80 00 ERRORFRAME
> > bus-error
> > error-counter-tx-rx{{128}{0}}
> > (000.001982) can0 20000080 [8] 00 00 00 00 00 00 80 00 ERRORFRAME
> > bus-error
> > error-counter-tx-rx{{128}{0}}
> >
> > (( Then a continous flood, exactly similar to the above packet, appears.
> > Unfortunately this flooding is a firmware problem. ))
> >
> > <-- Replug the cable, after a good amount of time -->
> >
> Where are the reverse state transitions?
> >

Hmmm...

[ ... ]
>
> Reverse state transitions are missing from the logs. See comments above.
>

When the device is on the _receiving_ end, and I unplug the CAN cable after
introducing some noise to the level of reaching WARNING or PASSIVE, I
receive a BUS_ERROR event with the rxerr count reset back to 0 or 1. In
that case, the driver correctly transitions back the state to ERROR_ACTIVE
and candump produces something similar to:

(000.000362) can0 2000008C [8] 00 40 40 00 00 00 00 01 ERRORFRAME
controller-problem{}
protocol-violation{{back-to-error-active}{}}
bus-error
error-counter-tx-rx{{0}{1}}

which is, AFAIK, the correct behaviour from the driver side.

Meanwhile, when the device is on the _sending_ end and I re-plug the CAN
cable again. Sometimes I receive events with txerr reset to 0 or 1, and
the driver correctly reverts back to ERROR_ACTIVE in that case. But on
another times like the quoted case above, I don't receive any events
resetting txerr back -- only data packets on the bus.

So, What can the driver do given the above?

Thanks,
Darwish

P.S. just in case, I'll also re-check now if the driver unintentionally
drops any important events resetting the txerr count back after a CAN
cable replug -- preventing the code from returning to ERROR_ACTIVE in
the process.