BeagleBone Black Ethernet PHY issues

[Geert Uytterhoeven]

Hi all,

During the last few months, booting kernels on BeagleBone Black
sometimes fails with:

    +SMSC LAN8710/LAN8720 4a101000.mdio:00: probe with driver SMSC
LAN8710/LAN8720 failed with error -5
     davinci_mdio 4a101000.mdio: phy[0]: device 4a101000.mdio:00,
driver SMSC LAN8710/LAN8720
     soc_device_match(cpsw_soc_devices): no match
     cpsw-switch 4a100000.switch: initialized cpsw ale version 1.4
     ...
     am335x-phy-driver 47401300.usb-phy: dummy supplies not allowed
for exclusive requests (id=vbus)
    +cpsw-125mhz-clkctrl:0014:0: failed to disable
     am335x-phy-driver 47401b00.usb-phy: using DT
'/ocp/target-module at 47400000/usb-phy at 1b00' for 'reset' GPIO lookup
     ...
     cpsw-switch 4a100000.switch: starting ndev. mode: dual_mac
    -SMSC LAN8710/LAN8720 4a101000.mdio:00: attached PHY driver
(mii_bus:phy_addr=4a101000.mdio:00, irq=POLL)
    -cpsw-switch 4a100000.switch eth0: Link is Up - 100Mbps/Full -
flow control off
    -Sending DHCP requests ., OK
    -IP-Config: Complete:
    -[...]
    +cpsw-switch 4a100000.switch: phy
"/ocp/interconnect at 4a000000/segment at 0/target-module at 100000/switch at 0/mdio at 1000/ethernet-phy at 0"
not found on slave 0
    +[HANG]

Adding debug prints to smsc_phy_probe() makes the issue go away, so it
must be timing related.

Adding specific debug prints in the failure case gives:

    SMSC LAN8710/LAN8720 4a101000.mdio:00: genphy_read_abilities:2859:
phy_read(MII_BMSR) failed -EIO
    SMSC LAN8710/LAN8720 4a101000.mdio:00: phy_probe:3613:
genphy_read_abilities() failed -EIO
    SMSC LAN8710/LAN8720 4a101000.mdio:00: probe with driver SMSC
LAN8710/LAN8720 failed with error -5

and later:

    Generic PHY 4a101000.mdio:00: genphy_read_abilities:2859:
phy_read(MII_BMSR) failed -EIO
    Generic PHY 4a101000.mdio:00: phy_probe:3609:
genphy_read_abilities failed -EIO
    cpsw-switch 4a100000.switch: phy
"/ocp/interconnect at 4a000000/segment at 0/target-module at 100000/switch at 0/mdio at 1000/ethernet-phy at 0"
not found on slave 0

Adding debug prints to __mdiobus_read() and davinci_mdio_read() gives:

    mdio_bus 4a101000.mdio: davinci_mdio_read:444:
readl(&data->regs->user[0].access) = 0x3a0ffff
    mdio_bus 4a101000.mdio: __mdiobus_read:900: davinci_mdio_read failed -EIO

but this is a different (and unimportant?) early failure from
smsc_phy_config_intr(), and that debug print actually makes the issue go
away, too.

Ignoring the early failure reveals that phy_read(MII_BMSR) failed due
to:

    mdio_bus 4a101000.mdio: davinci_mdio_read:446:
readl(&data->regs->user[0].access) = 0x20ffff

Anyone with a clue?
Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds