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

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Date:	Wed, 21 Jan 2015 17:13:45 +0100
From:	Wolfgang Grandegger <wg@...ndegger.com>
To:	"Ahmed S. Darwish" <darwish.07@...il.com>
Cc:	Andri Yngvason <andri.yngvason@...el.com>,
	Olivier Sobrie <olivier@...rie.be>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Linux-CAN <linux-can@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 2/5] can: kvaser_usb: Consolidate and unify state change handling

On Wed, 21 Jan 2015 10:36:47 -0500, "Ahmed S. Darwish"
<darwish.07@...il.com> wrote:
> 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  

For a bus-errors I would also expcect some more information in the
data[2..3] fields. But these are always zero.

>> >  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.

Well, the firmware seems to report *only* bus-errors via
CMD_CAN_ERROR_EVENT
messages, also carrying the new state, but no CMD_CHIP_STATE_EVENT just
for
the state changes.

> So, What can the driver do given the above?

Little if the notification does not come.

Wolfgang.

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