[etherlab-dev] EoE patchs and questions

[Graeme Foot]

Hi,

I've been setting up my system to use EoE (Ethernet over EtherCAT) with an RTAI user space application.

I've updated my master to revision 33b922ec1871 (default branch) and applied the gavinl (Gavin Lambert) patch set 20171108.
Linux 2.6.32.11
RTAI 3.8.1


Firstly I have a bit of a different use case for my EoE.  The current implementation auto creates and removes the eoe interfaces as the EoE capable slaves are configured and removed.  This means the interface is not available until the slave is scanned, and is not available if it is removed.  The eoe interface is also temporarily destroyed on a bus rescan.  In my use case I want to bridge the eoe interface to a real Ethernet interface.  So I want the eoe interface to always exists whether the slave is plugged in or not.

So the first patch does a few things:
1) adds explicit eoe_addif and eoe_delif tool functions so that you can manually add/remove an eoe iface without the slave existing
2) no longer deletes and eoe iface if the slave disappears
3) will relink a slave to an eoe iface when it is configured
4) will let you configure eoe ifaces via the sysconfig/ethercat config file
5) will let you turn off auto creation of eoe ifaces via the sysconfig/ethercat config file
6) no longer keeps slaves with EoE capability in OP mode when the master is deactivated

The above is made possible by using the netif_carrier_on() and netif_carrier_off() functions of the iface.  (The same as having a normal network interface up, but not plugged in.)

The other thing the patch does is fix a race condition bug in the eoe iface code.  The current implementation uses a struct list_head queue with a semaphore to protect it between the iface tx callback and the ethercat thread.  Sleeps are not allowed in the ifaces tx callback as it is in an interrupt context.  To fix this I have changed the queue to a ring buffer so that it no longer needs a lock.

FYI, when the race condition occurred I was getting:
BUG: scheduling while atomic
Call Trace:
[<c0146aa2>] ? ktime_get_real+0x0/0x29
[<c0146987>] ? ktime_get+0x0/0x88

Florian you may be interested in this patch, especially the bug fix part.


The second patch is so that I can run the EoE pump without callbacks.  As I am using a user space RTAI application I cannot use callbacks as they would need to call back from a kernel context to the user space context.  Instead I am running a thread in my application that makes calls into EtherCAT in a similar fashion to the masters EoE thread.  I have created two functions (ecrt_master_eoe_is_open() and ecrt_master_eoe_process()) to call without application locks as the locks only need to be around the ecrt_master_receive() and ecrt_master_send_ext() calls.


Now for the question.  I have been hammering my test rig pretty hard with various communications (pings with multiple fragments multiple times a second from both directions, SDO calls to the EoE slave without a pause approx. 100 per second).  Every now and then (after around 10 to 30 minutes with the above tests) the receive mailbox (SM1) of the EoE slave stops responding (slave to master).  CoE reads to the slave also fail.  The transmit mailbox still continues to function.  The RX SM1 status register continually returns a zero value.  I have found that if I send the command below the receive mailbox starts to function again (until it doesn't):

  ethercat reg_write -p3 0x808 -tuint64 0

Has anyone else come across this?  At the moment I suspecting a Slave firmware bug (EL6614).  Does anyone have any other ideas?


Regards,
Graeme Foot.



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