Hi, I have added socketcan (trunk rev. 1033 from 8/11/2009) to a Linux board
support package for an ARM9-based processor running at 208 MHz. The Linux
kernel version is 2.6.27.8. The environment has busybox and no suitable
netlink interface (ip command doesn't allow setting CAN properties) so I can
use the sysfs interface only. The CAN bitrate is 250 kbps and I am using
max. clock at the SPI interface to the MCP2515 (10 MHz). We are using the
CAN RAW driver.
In principle the setup works, but we appear to be dropping CAN packets at
the driver level. We have added several filters in the application level CAN
driver, and these filters appear to work under nominal message traffic
loads, but when we increase the message traffic on the CAN bus, the
controller driver appears to drop packets.
Here is the code snippet for the software filters that we have added in the
application level driver:
rfilter[0].can_id = 0x41;
rfilter[0].can_mask = 0xFF;
rfilter[1].can_id = 0xFFF1D8;
rfilter[1].can_mask = 0xFFFFFF;
rfilter[2].can_id = 0xFFF2D8;
rfilter[2].can_mask = 0xFFFFFF;
rfilter[3].can_id = 0xEAFF00;
rfilter[3].can_mask = 0xFFFF00;
setsockopt(canSocket, SOL_CAN_RAW, CAN_RAW_FILTER, &rfilter,
sizeof(rfilter));
We do a non-blocking (flags = MSG_DONTWAIT) call to recvfrom() at a 10 msec
update rate. We are generating the following msgs at the given rates:
0x18EA1D41 (filter[0]) at once per 5 secs rate.
0x18FEF341 (filter[0]) at once per second rate.
0x18FFF1D8 (filter[1]) at once per 100msecs rate.
We are additionally broadcasting messages that do not pass any filters to
make up a 300 messages per second traffic load.
We have broadcast and dropped the following messages, apparently at the
controller driver level, over a run of approx. 16 minutes and 30 seconds:
0x18EA1D41 - broadcast 183 times received at app driver 180
0x18FEF341 - broadcast 997 times received at app driver 982
0x18FFF1D8 - broadcast 9460 times received at app driver 9290
Can someone give me any hints on how to troubleshoot this? Is there any
debug output available that could help? Right now I don't even know at which
level the frames are dropped.
Thanks,
Chris
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