Re: [PATCH v1] net: phy: fix auto-negotiation stall due to unavailable interrupt

[David Miller]

From: Alexander Kochetkov <al.kochet@xxxxxxxxx>
Date: Thu, 20 Apr 2017 14:00:04 +0300

> The Ethernet link on an interrupt driven PHY was not coming up if the Ethernet
> cable was plugged before the Ethernet interface was brought up.
> 
> The patch trigger PHY state machine to update link state if PHY was requested to
> do auto-negotiation and auto-negotiation complete flag already set.
> 
> During power-up cycle the PHY do auto-negotiation, generate interrupt and set
> auto-negotiation complete flag. Interrupt is handled by PHY state machine but
> doesn't update link state because PHY is in PHY_READY state. After some time
> MAC bring up, start and request PHY to do auto-negotiation. If there are no new
> settings to advertise genphy_config_aneg() doesn't start PHY auto-negotiation.
> PHY continue to stay in auto-negotiation complete state and doesn't fire
> interrupt. At the same time PHY state machine expect that PHY started
> auto-negotiation and is waiting for interrupt from PHY and it won't get it.
> 
> Signed-off-by: Alexander Kochetkov <al.kochet@xxxxxxxxx>
> Cc: stable <stable@xxxxxxxxxxxxxxx> # v4.9+

So... what are we doing here?

My understanding is that this should fix the same problem that commit
99f81afc139c6edd14d77a91ee91685a414a1c66 ("phy: micrel: Disable auto
negotiation on startup") fixed and that this micrel commit should thus
be reverted to improve MAC startup times which regressed.

Florian, any guidance?