Hi Oliver,
On 8/29/22 15:53, Oliver Hartkopp wrote:
Hi Jacob,
On 29.08.22 15:20, Jacob Kroon wrote:
Hi Wolfgang and Marc,
On 8/29/22 11:14, Jacob Kroon wrote:
On 8/26/22 13:24, Jacob Kroon wrote:
On 8/25/22 15:25, Jacob Kroon wrote:
Hi,
I am using a CM-ITC board
(https://www.compulab.com/products/computer-on-modules/cm-itc/)
with an application that uses the CAN interface. After a while of
successfully sending packets, sendto() starts returning ENOBUFS. I
wait a whole second and try to send, several retries, but I get
ENOBUFS every time. I'm using kernel 5.15.59, and I've tried both
the pch_can and c_can_pci driver, but both show the same error.
In the console I see several of:
can0: can_put_echo_skb: BUG! echo_skb 0 is occupied
I've also tried to increase the txqueuelen to 1000, as suggested here
https://stackoverflow.com/questions/40424433/write-no-buffer-space-available-socket-can-linux-can
but I think that if I increase the queuelen the threads just block
forever in sendto() (sockets are opened in blocking mode)
If I bring down the interface with
ifconfig can0 down
ifconfig can0 up
the transmitting does get unblocked.
Is there anything I can do to debug this further ? Any other ideas ?
First I get the print:
can_put_echo_skb: BUG! echo_skb 0 is occupied!
then netif_stop_queue() is called from here:
https://github.com/torvalds/linux/blob/master/drivers/net/can/c_can/c_can_main.c#L469
and then there is no call to netif_start_queue(), so the bus hangs.
Switching back to the pch_can driver. I'm guessing here but it would
seem that the driver is not receiving the TX interrupt for
'PCH_TX_OBJ_END' that would wake up the netif queue, since with the
changes below I can't reproduce the hang, although I'm still seeing a
lot of "echo_skb <x> is occupied!":
diff --git a/drivers/net/can/pch_can.c b/drivers/net/can/pch_can.c
index 964c8a09226a..75ad2272d9b2 100644
--- a/drivers/net/can/pch_can.c
+++ b/drivers/net/can/pch_can.c
@@ -719,8 +720,7 @@ static void pch_can_tx_complete(struct
net_device *ndev, u32 int_stat)
PCH_IF_MCONT_DLC);
stats->tx_bytes += dlc;
stats->tx_packets++;
- if (int_stat == PCH_TX_OBJ_END)
- netif_wake_queue(ndev);
+ netif_wake_queue(ndev);
}
Is there a recommended driver for the Intel EG20T PCH CAN controller ?
pch_can or c_can_pci ?
I'm very happy that you show up with this question!
AFAIK the PCH_CAN driver was contributed by some OKI developers on
behalf of Intel to support their EG20T platform. This driver has not
been worked on for years now.
Later the C_CAN driver got its PCI support which should have made the
PCH_CAN driver obsolete as they are both using the C_CAN IP core.
So my suggestion would be to work with the well maintained c_can_pci and
mark the pch_can obsolete in the Linux kernel.
Ok.
IIRC Marc is very experienced with the C_CAN driver but he is still on
vacation this week.
Regarding your problem:
"BUG! echo_skb 0 is occupied" should never show up but I wonder if you
probably have another CAN specific problem with your setup.
Did you set up a CAN network with at least two CAN nodes, identical
bitrate settings and 2x120 Ohms (== 60 Ohms) termination between CAN_L
and CAN_H?
I have double checked that both endpoints of the network are terminated
with 120Ohm resistors, and when I check CAN_H/CAN_L in an oscilloscope
they look ok, and within the spec. voltage levels.
Do you have another CAN node which can be attached to the EG20T setup
(e.g. some ECU or an USB CAN adapter)?
Yes I do have a CAN analyser from Microchip. I guess I can record all
traffic with the analyzer, and compare it to what I see with "candump
can0" on the host. Or do you have some other suggestion ?
Thanks for responding,
Jacob
