Re: [PATCH 4/4] can: flexcan: Disable error irq when in error passive

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

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On 08/14/2014 03:19 PM, Alexander Stein wrote:
> On Thursday 14 August 2014 13:18:47, Marc Kleine-Budde wrote:
>> On 08/12/2014 03:43 PM, Alexander Stein wrote:
>>> If the error irq is enabled and the hardware is trying to send a CAN
>>> message to an open bus it will receive a lot of acknowledge errors and
>>> generating lots of interrupts. So error interrupts are disabled when
>>> entering error passive and reenable them when leaving error passive.
>>> We can only leave error passive by receiving CAN frames in which case NAPI
>>> is scheduled anyway or by sending more CAN frames when send is possible
>>> again. But with the transition of error counters from 96 to 95 the flags
>>> TX_WRN and RX_WRN are gone again, so we need to remember the flags state
>>> to detect a change there.
>>
>> There are use cases where the error interrupts even when in passive mode
>> are essential. You have a use case, where you'd like to turn them off
>> completely. Have you had a look at the bus error limiting patches?
> 
> Do you mean "[PATCH v7] flexcan: add err_irq handler for flexcan" from Zhao Qiang?

No, sorry I assumes you were following the discussion with Matthias
Klein and Sebastian Andrzej Siewior [1].

I was talking about the patch from
http://comments.gmane.org/gmane.linux.can/4070

The idea behind this series is to not enable the bus error interrupt
right after it has served, but after a configurable delay, e.g. 100ms.
Even with an open or otherwise faulty but, you then receive just 10
error frames per second.

Marc

[1] http://thread.gmane.org/gmane.linux.can/6271
[2] http://thread.gmane.org/gmane.linux.can/6280

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