Re: flexcan napi poll and error frames

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

On fös 24.okt 2014 16:36, Steffen Rose wrote:
> Hello,
>
> Am Freitag, 24. Oktober 2014, 16:04:56 schrieben Sie:
>>> We can do little if the CAN controller does not notify the Software
>>>> via interrupt.
>>> Yes, that's why I wanted to figure out if it's a controller problem or
>>> not.
>>> Turns out it's a controller problem, but perhaps we can work around it?
>>> E.g. if we check esr for state changes every time someone transmits a
>>> frame, both of these problems would go away. Would it be unacceptable
>>> overhead to do so?
>> I've just confirmed that this "fix" works, but only if berr-reporting is
>> enabled.
> Is this workaround working in case of an open CAN Bus?
> (Ack error situation)
Yes
> The flexcan can generate an error interrupt after every CAN bus error. But in 
> case of an error situation the interrupt load would be very high (e.g. short 
> circuit of the CAN).
>
That's what berr-reporting does, right? Considering that when the bus is
flooded with errors, things are in a pretty bad shape anyway, I think it's
not really going to contribute much to the over-all mess to just leave the
error interrupts on all the time. It's far worse if the user doesn't get
the correct error state.

Anyway, defensive measures can be taken. When the bus has reached
error-passive, the driver is not going to need those interrupts any more
so it could turn off the interrupts until the bus goes to bus-off or back
down to warning or active; except when berr-reporting is enabled.

--
Andri