Hi,
only one comment :
It is not anbsolutely necessary to disable bus error interrupt " a new
bus error in terrupt is not possible until the ecc register is read out
once".
only disabling reading of ecc in isr will disable new bei generation.
Best Regards
Steph
Wolfgang Grandegger wrote:
Hi Sebastian,
Sebastian Smolorz wrote:
Wolfgang Grandegger wrote:
Sebastian Smolorz wrote:
Last summer we had a discussion about the BEI issue on the
socketcan-ML.
Two additional handling policies popped up:
1. The interface could restart itself after an amount of BEIs, thus
taking responsibility from the user application.
2. The BEI could be completely disabled if no one is interested in this
type of error frame.
I tried to implement 2. for SJA1000, but re-enabling the BIE on the fly
does not work. :-(. The controller requires a re-start of the device to
get the bus error reporting back to work.
Oh, really? I wasn't aware of this.
Well, I got it working. Reading the ECC register after re-enabling the
bus error interrupts fixed the problem:
if (CAN_STATE_OPERATING(dev->state)) {
chip->write_reg(dev, SJA_IER, chip->ier); /* update on the fly */
chip->read_reg(dev, SJA_ECC);
}
Maybe it is time to think about the implementation of these policies as
more and more users seem to run into the BEI issue with a disconnected
bus. Wolfgang, Jan, what is your opinion?
Well, solution 2. with the limitations mentioned above is therefore less
attractive because it interrupts the CAN traffic.
True.
Back to our preferred solution 1. Attached is a patch for review
including some other fixes and suggestions accumulated over time:
* ksrc/drivers/can/*: To avoid unnecessary bus error interrupt
flooding, the option CONFIG_XENO_DRIVERS_CAN_BUS_ERR now allows to
enable bus error interrupts "on demand" only if an application is
interested in such errors. It is automatically selected for CAN
controllers supporting bus error interrupts like the SJA1000.
* include/rtdm/rtcan.h: Add some doc on bus-off and bus-error error
conditions and the restart policy.
* src/utils/can/rtcanconfig.c: Controller mode settings and doc
has been corrected.
The Socket-CAN implementation actually restarts the CAN controller
after a certain
amount of bus error interrupts (200 by default) which matches your first
policy above. But in RT-Socket-CAN, we do not automatically re-start the
device by purpose. Therefore I tend to just stop the device. It's then
up to the application to restart it. What do you think?
No fundamental objections but it would be best if an application would
be informed of this special situation e.g. through an error frame with
the meaning "controller was stopped because of a disconnected bus
after trying to send 200 times the same message".
A question pops up in this context: Why do we define CAN_ERR_RESTARTED
if we never do this? Only to be compatible with Socket-CAN? Then I
would propose to extend the documentation by pointing out that this
will not appear under RT-Socket-CAN.
Let's wait if solution 1. is sufficient. maybe we need 2. later as well.
Wolfgang.
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