Hi Wolfgang, On 03/09/2017 09:45 AM, Wolfgang Grandegger wrote: > Hello Akshay, > > Am 09.03.2017 um 13:34 schrieb Akshay Bhat: >> >> 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. > >> 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 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
