Re: [PATCH net-next] net: phy: marvell: Ensure SGMII auto-negotiation is enabled for 88E1111

On Sat, 2021-02-13 at 01:09 +0000, Russell King - ARM Linux admin wrote:

On Fri, Feb 12, 2021 at 06:26:29PM -0600, Robert Hancock wrote:

quoted

When 88E111 is operating in SGMII mode, auto-negotiation should be enabled

88E1111.

yup..

quoted

on the SGMII side so that the link will come up properly with PCSes which
normally have auto-negotiation enabled. This is normally the case when the
PHY defaults to SGMII mode at power-up, however if we switched it from some
other mode like 1000BaseX, as may happen in some SFP module situations,
it may not be.

Do you actually have a module where this applies?

I have modules that do come up in 1000base-X mode, but do switch to
SGMII mode with AN just fine. So I'm wondering what the difference is.

I saw this with a Finisar FCLF8520P2BTL, which defaults to 1000Base-X with
host-side auto-negotiation disabled. So presumably the auto-negotiation
disabled state carries over when it is switched to SGMII mode. I previously
wrote a patch ("net: phy: marvell: add special handling of Finisar modules with
88E1111") which enabled auto-negotiation for 1000Base-X mode, but we are trying
to switch over to using SGMII with these now.

-- 
Robert Hancock
Senior Hardware Designer, Calian Advanced Technologies
www.calian.com