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

Lothar Waßmann
2015-11-30T06:56:17Z

Hi,

> From: Lothar Waßmann <LW@KARO-electronics.de> Sent: Friday, November 27, 2015 9:39 PM
> > To: Andrew Lunn; David S. Miller; Estevam Fabio-R49496; Kevin Hao; Lothar
> > Waßmann; Lucas Stach; Duan Fugang-B38611; Philippe Reynes; Russell King;
> > Uwe Kleine-König; linux-kernel@vger.kernel.org; netdev@vger.kernel.org;
> > Stefan Agner
> > Subject: [PATCH] net: fec: fix enet_out clock handling
> >
> > 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 [...]
> >
> > Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
> > ---
> > drivers/net/ethernet/freescale/fec_main.c | 34 +++++++++++++------------
> > ------
> > 1 file changed, 14 insertions(+), 20 deletions(-)
> >
>
> When MAC is not ready with clocks disabled, it is not necessary to supply clock for PHY. In fact, PHY also is not ready, why does it need clock ?
> For your problem, you must add PHY reset in your dts file to resolve your problem.
>
The phy-reset-gpio property is set in the DTB. But fec_reset_phy()
which asserts the RESET is only called from within the probe() function.
It should probably be called from fec_restart() instead?

Lothar Waßmann