Re: [PATCH] net: fec: fix enet_out clock handling

Lothar Waßmann
2015-11-30T05:37:02Z

Hi,

> On Fri, Nov 27, 2015 at 02:39:10PM +0100, Lothar Waßmann wrote:
> > When ENET_OUT is being used as reference clock for an external PHY,
> > the clock must not be disabled while the PHY is active. Otherwise the
> > PHY may lose its internal state and require a reset to become
> > functional again.
> >
> > A symptom for this bug is a network interface that constantly toggles
> > between UP and DOWN state:
> > fec 800f0000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
> > fec 800f0000.ethernet eth0: Link is Down
> > fec 800f0000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
> > fec 800f0000.ethernet eth0: Link is Down
>
> Hi Lothar
>
> When does this up/down happen? During normal operation when the link
> is administrative up?
>
If booting with NFSROOT the rootfs cannot be mounted, because when the
interface is brought up the PHY starts toggling the link state.

> When did this start happening? Did it happen before
> 8fff755e9f8d net: fec: Ensure clocks are enabled while using mdio bus
>
No. The behaviour started exactly with this commit.

Lothar Waßmann