IMX8MQ Ethernet RX CRC problems after upgrade from linux 4.14.98 to 5.4.24

[t_spil]

Hi,

We are using a variscite iMX8MQ board attached to a custom PCB, it's been running well with linux 4.14.98. Recently we tried tried to upgrade the linux kernel from 4.14.98 to 5.4.24 and yocto build system from sumo to zeus so we could use newer versions of some executables.

However after some testing we found that one of our applications had issues uploading data to the iMX8. Running ethtool -S eth0 showed that there were a lot of rx_crc_errors occurring. In the table below you can find a comparison between the software versions. We're running exactly the same test, on the same hardware with exactly the same source code for the application doing the data exchange.

Linux 4.14.98	Linux 5.4.24
rx_packets: 55659 rx_broadcast: 96 rx_multicast: 176 rx_crc_errors: 0	rx_packets: 5227 rx_broadcast: 52 rx_multicast: 59 rx_crc_errors: 3434

It clearly shows that some kind of problem has been introduced. I had a look at the changes in the source code of the ethernet driver fec_main.c, but nothing stood out that would explain this.

Do you know what the could have caused this regression? And is there some way to fix this.

Thanks,
Twan

[igorpadykov]

Hi Twan

one can check enet pad settings for both cases in pinctrl_fec1: fec1grp {

https://source.codeaurora.org/external/imx/linux-imx/tree/arch/arm64/boot/dts/freescale/imx8mq-evk.d...

https://github.com/varigit/linux-imx/blob/imx_5.4.24_2.1.0_var01/arch/arm64/boot/dts/freescale/imx8m...

also one can post issue on variscite wiki:

http://variwiki.com/index.php?title=DART-MX8M

Best regards
igor

[t_spil]

Hi Igor,

Those enet pad settings haven't changed between the 4.14 and 5.4 version. We have applied all changes that were made to the device tree blob in between the version.

Is there anything else you can think of?

Thanks,
Twan

[igorpadykov]

Hi Twan

when you say "upgrade the linux kernel from 4.14.98 to 5.4.24" what do you mean,

only changed some parts of software, leaving some unchanged ?

Suggest to rebuild all image from scratch including all software components:

uboot, linux e.t.c. following all versions compatbility as described in DART8M Release Notes :

https://variwiki.com/index.php?title=DART-MX8M_Release_Notes&release=RELEASE_ZEUS_V1.0_DART-MX8M

Best regards
igor

[t_spil]

Hi Igor,

For the upgrade we started from scratch following the guide that you linked. It differs between boards how many crc errors occur, for some boards it's over 50% of the packets. This makes even using scp to upload something to the board almost impossible with speeds of 10 kb/s over a wired local network connection. Some other boards only have 5% of the packets drop due to crc errors. But all of them have zero dropped packets due to crc errors on the sumo version.

Is there anything else that could be causing these issues?

Thanks,
Twan