CAN messages being lost on i.MX25 with flexcan - continued (was CAN messages being lost on i.MX25 with flexcan - 2012-04-19)

[Martin Kozusky <mkozusky@kkmicro.cz>]

Hello,
after more than year I'm back with CAN fifo overrun problems on i.MX25 board.
(it was good enough earlier, if some frames were lost, but not this time)

I have 2 flexcan interfaces, each receiving around 1100 msgs/s (situation is a little better if I use just one iface, but I need both)
I just configure them and then run:

I=0; while [ $I -le 20 ]; do dd if=/dev/zero of=/mnt/mmcblk0p1/test bs=512 count=200; sync; sleep 1; I=$(($I+1)); done
(simulate writing to SDcard with 100KB blocks in 1 sec intervals)

and start sending data from another device.

I am not running any other program (like candump etc) to read from CAN.

this is what is shown after I finish sending 35777 packets (both interfaces now connected to same bus so they should receive same data) with ip -d -s link show can0/1

2: can0: <NOARP,ECHO> mtu 16 qdisc pfifo_fast state DOWN qlen 10
     link/can
     can <LISTEN-ONLY> state STOPPED (berr-counter tx 0 rx 0) restart-ms 0
     bitrate 250000 sample-point 0.857
     tq 285 prop-seg 5 phase-seg1 6 phase-seg2 2 sjw 1
     flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
     clock 66500000
     re-started bus-errors arbit-lost error-warn error-pass bus-off
     0          0          0          1          1          0
     RX: bytes  packets  errors  dropped overrun mcast
     151769     19000    1699    0       1699    0
     TX: bytes  packets  errors  dropped carrier collsns
     0          0        0       0       0       0
root@vmx25 /opt/waytracer$ /root/utils/ip -d -s link show can1
3: can1: <NOARP,ECHO> mtu 16 qdisc pfifo_fast state DOWN qlen 10
     link/can
     can state STOPPED (berr-counter tx 0 rx 0) restart-ms 0
     bitrate 250000 sample-point 0.857
     tq 285 prop-seg 5 phase-seg1 6 phase-seg2 2 sjw 1
     flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
     clock 66500000
     re-started bus-errors arbit-lost error-warn error-pass bus-off
     0          0          0          0          0          0
     RX: bytes  packets  errors  dropped overrun mcast
     157377     19696    2664    0       2664    0
     TX: bytes  packets  errors  dropped carrier collsns
     0          0        0       0       0       0


With just one iface used:

2: can0: <NOARP,ECHO> mtu 16 qdisc pfifo_fast state DOWN qlen 10
     link/can
     can <LISTEN-ONLY> state STOPPED (berr-counter tx 0 rx 0) restart-ms 0
     bitrate 250000 sample-point 0.857
     tq 285 prop-seg 5 phase-seg1 6 phase-seg2 2 sjw 1
     flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
     clock 66500000
     re-started bus-errors arbit-lost error-warn error-pass bus-off
     0          0          0          1          1          0
     RX: bytes  packets  errors  dropped overrun mcast
     233277     29201    1483    0       1483    0
     TX: bytes  packets  errors  dropped carrier collsns
     0          0        0       0       0       0


Too many packets are lost.

I tried to play with FLEXCAN_NAPI_WEIGHT (quota for napi) and that didn't hepl too much, if I put it too high then the system response was slow and packets still lost, also tried to change priority of CAN interrupts with (don't know if correctly)
   // imx_irq_set_priority(43,14);
   // imx_irq_set_priority(44,14);

But it didn't help either.


Does anybody have any idea how not to lose any packets? :)


Thanks,
Martin