Dual SJA1000 can controllers on SMP system.

[Mirza Krak <mirza.krak@hostmobility.com>]

Dear Sirs.

I am running a 3.1.10 kernel on Nvidia Tegra 2 CPU (Dual Core). Not 
vanilla kernel (Linux4Tegra).

We are using dual can controllers connected on th external data bus on 
our custom hardware. The can controllers are SJA1000.

Driver that is used is vanilla sja1000 driver (sja1000.c)

Now to the issue at hand. Will try my best to explain our scenario and 
issue:
     1. The two can controllers are connected with each other with a 
loop-back.
     2. What we are attempting is to send data on both controllers in 
two separate processes. We are using following command "cansequence can0 
-p &" and "cansequence can1 -p &". With a bit-rate configured to 1 Mbit/s.
     3. What we see when we attempt the above is that one of the 
controllers stop sending and the software buffer gets filled up. When it 
stops varies but usually after a few packets are sent.

After some digging we came to this conclusion. The two cansequence 
processes end up on different CPU cores. The process that ends up in 
CPU1 is the one that always stops transmitting.

Workarounds that we have seen that works is
     1. Disable dual core with kernel argument "maxcpus=1".
     2. Forcing the cansequence processes to CPU0 with "taskset" command.

My question to you is if anyone has tested the SJA1000 driver on an SMP 
system or anything similar.
-- 
Med Vänliga Hälsningar / Best Regards
Mirza

*******************************************************************
Mirza Krak
Host Mobility AB
mirza.krak@hostmobility.com
Anders Personsgatan 12, 416 64 Göteborg
Sweden
www.hostmobility.com <http://www.hostmobility.com>
Direct: +46 31 31 32 704
Phone: +46 31 31 32 700
Fax: +46 31 80 67 51
Mobile: +46 730 28 06 22
*******************************************************************