Re: [PATCH net v3] net: phy: mediatek-ge: disable EEE on the MT7530 PHY

On Fri, Sep 04, 2026 at 11:28:00PM +0300, Vladislav Karmanov wrote:

The MT7530 internal GE PHY advertises EEE by hardware default, but its
EEE support is defective: with EEE advertised, some link partners fail
to establish a stable link. On a 2-pair (4-wire) cable where both ends
advertise gigabit, 1000BASE-T training cannot succeed, and instead of
falling back to 100 Mbps the port loops, so no link or DHCP lease is
ever obtained. MediaTek confirms the hardware is the root cause (Landen
Chao, 2021): "EEE of the 10-year-old MT7530 internal gephy has many IOT
problems, so it is recommended to disable its EEE."

mtk_gephy_config_init() used to clear the EEE advertisement early, but
commit af3b4b0e59de ("net: phy: mediatek-ge: do not disable EEE
advertisement") removed that on the rationale that the DSA subdriver
already performs an early disable. That holds for MT7531, whose
mt7531_setup() clears MDIO_AN_EEE_ADV on each switch PHY, but not for
the MT7530 PHY: neither the MT7621 integrated switch nor the dedicated
MT7530 IC ever had such a loop, so removing it left those boards
without any working early EEE disable and the link flapping came back.

Since the broken hardware is the PHY, fix it in the PHY driver so it
covers all users of this PHY, integrated in a switch or standalone:

  - clear MDIO_AN_EEE_ADV in probe(), before anything can negotiate
    EEE with the link partner;
  - call phy_disable_eee() so phylib does not write the advertisement
    back on later renegotiations and userspace cannot re-enable EEE.

Auto-negotiation then falls back to a stable 100 Mbps link instead of
looping at gigabit. Tested on ASUS RT-AX53U (MT7621): with a 2-pair
cable on the WAN port, a single clean 100 Mbps link comes up and a
DHCP lease is obtained, where the unpatched driver loops.

Fixes: af3b4b0e59de ("net: phy: mediatek-ge: do not disable EEE advertisement")
Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Vladislav Karmanov <redacted>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew