Hi Wolfgang,

On 03/09/2017 09:45 AM, Wolfgang Grandegger wrote:

Hello Akshay,

Am 09.03.2017 um 13:34 schrieb Akshay Bhat:

quoted

Hi Wolfgang,

Good question. I have not worked with MPC251x but the HI-311x performs
much better because HI-3110 features:
8 message FIFO (as opposed to 2 buffers on MPC2510)
20 MHz SPI interface (as opposed to 2.5 MHz on MPC2510)

As for the real world test results:

With RT patch applied to the kernel running on a i.MX6 Dual processor
(worst case interrupt latency of 50us as reported by cyclictest), there
are ZERO packet drops.
Tested with Kvaser Leaf sending 100 burst messages (back to back) every
40ms at a 1M CAN bit rate. 10 million messages were sent by the Kvaser
leaf and received successfully by the HI-311x driver.

This corresponds to a bus load of approx. 50%, I think?

The usecase I tested above was more like ~30% (data payload length was
randomized) but I did test with 50% bus load as well without any dropped
messages.

quoted

Even without the RT patch, I was able to get the packet drop to zero but
this was by moving the CAN/SPI IRQ threads to CPU1 instead of CPU0.

Vanilla Linux is more critical here due to higher latencies. With 2500
Messages per sec the RX FIFO (8 Messages) fills up within 3.2 ms... and
in a burst even quicker. That's already heavy load.

I agree with Vanilla Linux is more critical due to higher latencies,
however if the frequency governor is set to performance and CAN/SPI
threads are moved to another CPU (if that is an option) with SCHED_FIFO
setting, the driver is able to keep up even at high bit rates / bursts.

I understand SPI based CAN controllers are not ideal choice but for
users that do not have any other option, I feel this controller/driver
meets their need :)

Thanks,
Akshay