drivers: mdio: mdio_nxp_enet: Link goes up and down sporadically

[decsny]

NXP ENET MDIO driver has a bug where interrupt is not cleared properly causing phy link to go up and down sporadically.

[yuecelm]

I tried the bugfix as a cherry pick on the 3.7.0 release. Tested on board mimxrt1050_evk. Unfortunately the link downs are still happening:

[00:05:11.926,000] <inf> eth_nxp_enet_mac: Link is down
[00:05:12.526,000] <inf> eth_nxp_enet_mac: Link is up
[00:05:12.526,000] <inf> phy_mc_ksz8081: PHY 0 is up
[00:05:12.526,000] <inf> phy_mc_ksz8081: PHY (0) Link speed 100 Mb, full duplex

what is strange that I dont observe the log "phy_mc_ksz8081: PHY 0 is down" here like when I really unplug the cable

[decsny]

I tried the bugfix as a cherry pick on the 3.7.0 release. Tested on board mimxrt1050_evk. Unfortunately the link downs are still happening:

[00:05:11.926,000] <inf> eth_nxp_enet_mac: Link is down
[00:05:12.526,000] <inf> eth_nxp_enet_mac: Link is up
[00:05:12.526,000] <inf> phy_mc_ksz8081: PHY 0 is up
[00:05:12.526,000] <inf> phy_mc_ksz8081: PHY (0) Link speed 100 Mb, full duplex

what is strange that I dont observe the log "phy_mc_ksz8081: PHY 0 is down" here like when I really unplug the cable

can you please provide how to reproduce

[yuecelm]

I tried to reproduce it with samples/net/cloud/aws_iot_mqtt, but no success yet. My application does also include 2 UARTs for Modbus and M-Bus sensors and a SDHC card (littlefs formatted). I can say that my application did not had this link down behavior with zephyr release 3.6.0 and the mcux ethernet driver. When I use release 3.7.0 and switch back to deprecated mcux ethernet driver, I dont observe the link down anymore (>1 day uptime without link down). I try next week again to reproduce the link down behavior with a minimal example.