Re: [PATCH 3.19-rc3] c_can: SIE disabled when berr-reporting is off to reduce irq flood

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 01/18/2015 07:52 PM, Viktor Babrian wrote:
> 
>> NACK. The transitions are important for some applications. I've an not
>> yet mainlined series that limits the bus errors. I'm going to port them
>> to the current kernel tomorrow. Can you test it?
> 
> This controller simply does not have a warn->pass state transition 
> interrupt. The only way to accurately (right on time) report this 
> transition is to switch on all error interrupts (ie the status interrupt) 
> that cause interrupt flood in some scenarios e.g. when frame is not acked 
> by other parties.
> If we don't turn on the status interrupt, the warn->pass state transition 
> can be detected later on a successful rx/tx event (or when entering bus 
> off etc).
> 
> I have learned that the warn->pass transition interrupt is also missing 
> from other controllers as well (like Flexcan). Interrupt flood caused by 
> enabling error interrupts regardless of the berr-reporting state is an 
> issue there too.
> 
> Also note that when the system is flooded by these error interrupts, 
> system performace degrades so much that serial terminal echo becomes 
> annoyingly long. When this happens, I wonder how usable the "accurate" 
> state transition reports are anyway.

As I said, they are vital to some applications. The bus error limiting
series will follow.

Marc

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