On 11/11/19 10:48 AM, Joakim Zhang wrote: > I came across a strange phenomenon about wake up in Flexcan driver with > v5.4 kernel, I connected two i.MX7D-SDB board. > > I found that CAN frame which try to wake up the system will not be > received at another side in order. Like below case: > > Sender: cangen can0 -vv > can0 4D9 [8] 89 72 0C 5F C8 15 2D 3A > can0 0AA [8] B7 DC 14 61 7F A0 8E 40 > can0 304 [8] 42 5C D7 3B D6 1D 36 56 > can0 0D9 [7] B0 C3 1B 7B 9B 3A 19 > can0 66B [8] 8A B0 D9 56 00 46 76 48 > can0 22D [8] 44 4B FD 53 B2 D3 A5 33 > can0 47E [8] B9 6B 72 0B 4C 15 96 72 > can0 54C [3] 3F BE 8F > can0 7C1 [8] EE A7 B4 11 6C 80 8F 7D > can0 5D6 [5] EB 20 1E 3E DB > can0 794 [8] B1 56 9E 13 6D 88 CE 52 > can0 584 [1] 08 > > > > Receiver: candump can0 & > can0 0AA [8] B7 DC 14 61 7F A0 8E 40 > can0 304 [8] 42 5C D7 3B D6 1D 36 56 > can0 0D9 [7] B0 C3 1B 7B 9B 3A 19 > can0 66B [8] 8A B0 D9 56 00 46 76 48 > can0 22D [8] 44 4B FD 53 B2 D3 A5 33 > can0 4D9 [8] 89 72 0C 5F C8 15 2D 3A > can0 47E [8] B9 6B 72 0B 4C 15 96 72 > can0 54C [3] 3F BE 8F > can0 7C1 [8] EE A7 B4 11 6C 80 8F 7D > can0 5D6 [5] EB 20 1E 3E DB > can0 794 [8] B1 56 9E 13 6D 88 CE 52 > can0 584 [1] 08 > > You can see that wake up frame(can0 4D9 [8] 89 72 0C 5F C8 15 2D 3A) > will be received at 6^th , it’s hard to understand. - What did you do before wakeup? - Clean reboot? - ifdown/ifup? - sending other packets? - Does this happen on every wakeup? - Is the wake up frame always "received" as 6th frame? - Is the situation the same, if you add some delay between the frames, using the "cangen -g option"? - How big can you make the -g until the frames are received in order again? The reception path works like this: In the interrupt handler the rx-offload reads all mailboxes based on the iflag register. It iterates over all set mailboxes, starting with the first. All mailboxes are read including the rx-timestamp, sorted and added into a queue. At the end of the IRQ handler the queue is added to the per device queue thats read in the NAPI and pushed into the networking stack. Maybe something with the timestamp of the first packet is wrong, as the counter is only 16 bits wide, it will overflow quite often. Maybe you can trace_printk the mailbox number, timestamp and can_id in mailbox_read() and analyse output after wakeup. Feel free to post the output of the tracer here. regards, Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
Attachment:
signature.asc
Description: OpenPGP digital signature
