Re: flexcan napi poll and error frames

[Andri Yngvason <andri.yngvason@marel.com>]

On fös 24.okt 2014 10:43, Wolfgang Grandegger wrote:
> On Fri, 24 Oct 2014 10:26:11 +0000, Andri Yngvason
> <andri.yngvason@marel.com> wrote:
>> Hi,
>>
>> I was running some tests on my patches when I noticed the following:
>> If I have 2 flexcan devices on the bus, each sending to the bus using
>> cangen,and then I disconnect the cable to one of them, that device
>> will enter"error-warning" state, but it will not continue on to
>> "error-passive" as itshould.
>>
>> However, when I reconnect the cable, I get the "error-passive" message
>> followed by an "error-warning" and eventually "back-to-error-active".
> Yes, I think I observed that behaviour as well as you can see here:
> https://gitorious.org/linux-can/wg-linux-can-next/commit/bd3acb12dbb9551541d28ae8766c154d3cf6ed57.patch
Good to know.
>> Notice the time differences:
>> root@(none):~# candump -td -e can0,0~0,#FFFFFFFFFF
>>  (000.000000)  can0  20000004   [8]  00 08 00 00 00 00 00 00  
> ERRORFRAME
>>         controller-problem{tx-error-warning}
>>  (006.493209)  can0  20000004   [8]  00 40 00 00 00 00 00 00  
> ERRORFRAME
>>         controller-problem{back-to-error-active}
>>  (002.701331)  can0  20000004   [8]  00 08 00 00 00 00 00 00  
> ERRORFRAME
>>         controller-problem{tx-error-warning}
>>  (006.498567)  can0  20000004   [8]  00 20 00 00 00 00 00 00  
> ERRORFRAME
>>         controller-problem{tx-error-passive}
>>  (000.013915)  can0  20000004   [8]  00 08 00 00 00 00 00 00  
> ERRORFRAME
>>         controller-problem{tx-error-warning}
>>  (001.990695)  can0  20000004   [8]  00 40 00 00 00 00 00 00  
> ERRORFRAME
>>         controller-problem{back-to-error-active}
>>
>>
>> I suspect that the problem is that the driver doesn't receive any
>> interruptsother than the one for "error-passive" and so things
>> won't "weigh" enoughfor napi. There seems to be some truth in this
>> conjecture, because when Itried setting the napi weight to 1, the
>> message got through.
> Hm, why should it depend on NAPI. It does not delay messages for
> a long time. I think the problem is that the state change is not
> signalled my an interrupt but some time later when another event
> (message) occurs.
>  
Perhaps, but how do you explain that the message got through when I
set the weight to 1?
>> Another thing that I found peculiar was that I had to be sending on
>> both devices for the error states to change to anything other than
>> "error-warning".
> Well, the error reporting on the SJA1000 is perfect... on all other
> CAN controllers it's more or less worse.
>
Should we just ignore this problem then? I'd rather like to figure
out if this is problem with the controller or not. Do you remember
if you've had this problem with flexcan?

Andri.