FDCAN not working properly

[JYune]

I am trying to enable FDCAN on STM32MP157C. I modified Linux Kernel (STM32MP15-Ecosystem-v2.0.0) and U-Boot, following the steps explained in the Developer Package guide. I get these messages, which are suggesting I setup everything correctly.

root@stm32mp1:~# dmesg | grep m_can
[ 3.032730] m_can_platform 4400e000.can: m_can device registered (irq=51, version=32)
[ 44.537911] m_can_platform 4400e000.can can0: bitrate error 0.3%
[ 44.542503] m_can_platform 4400e000.can can0: bitrate error 0.3%

root@stm32mp1:/sys/kernel/debug/pinctrl/soc:pin-controller@50002000# cat pinconf-pins | grep CAN
pin 11 (PA11): alternate 9 (FDCAN1_RX) - push pull - floating - low speed
pin 12 (PA12): alternate 9 (FDCAN1_TX) - push pull - floating - low speed

The board seems to pass the internal loopback test as well (https://wiki.st.com/stm32mpu/wiki/How_to_send_or_receive_CAN_data#Hardware_self-test).

The problem is that I cannot get anything on the physical ports. What could have gone wrong?

[Olivier GALLIEN]

Hi @JYune​ 

We have a known bug with CAN we have already identified and pending to integrate :

You can find a version of patch here : https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b0342b87cad88894a989604df549e88ff47fb513

Olivier

[NBhat.1]

Hi Olivier,

I'm having the exact same problem as described in this issue. I'm testing FDCAN on our custom board based on STM32MP153C using Ecosystem v2.1.0 . Internal CAN loopback works fine but nothing on the physical pins. I also tried the kernel patch you suggested above but it didn't make any difference. I've also removed the "sleep" mode for the CAN pins and from m_can1 node from the kernel DT, but still no data on FDCAN1_TX pin when I try sending some data out. Am I missing something? Thanks.

[JYune]

@NBhat.1​ I disabled loopback and was able to get physical signals.

[NBhat.1]

Thanks @JYune​  I got it working with the above patch.