[OpenWrt-Devel] ar8216: question regarding ar8xxx_phy_config_aneg

[Heiner Kallweit]

On Fri, Nov 28, 2014 at 12:15 PM, Jonas Gorski <jogo at openwrt.org> wrote:

> On Fri, Nov 28, 2014 at 11:06 AM, Heiner Kallweit <hkallweit1 at gmail.com>
> wrote:
> > In my tests with AR8327 this callback was never called with an addr != 0.
> > Seems logical to me as it's called for the PHY attached to the net device
> > only.
> >
> > In most cases this is addr 0, just for AR8316 with port4_phy being set
> this
> > could be 4.
> >
> > This leads to two questions:
> >
> > 1. The current version of this function checks for "addr == 0" always,
> I'd
> > assume this is not correct for AR8316 and port4_phy being set.
> >
> > 2. As it seems to be called for the attached PHY addr only and in exactly
> > this case we do nothing: Can we simply replace this callback with a dummy
> > "return 0" ?
>
> Port4_phy being set means the switch operates in dual-mii mode.
>
> Most Atheros switches (including AR8327) support a dual-phy mode,
> where port 5 / phy 4 is split out from the rest of the switch and used
> as a single phy for a second ethernet mac. In these cases phy 4 is
> used like a standard phy, and the kernel needs to be able to configure
> autonegotiation or other features.
>
> Consequently you will only see the callback being called for addr != 0
> if the switch is in this mode and there is a second ethernet mac as
> the single wan port. I'm not sure if there are any OpenWrt supported
> devices with this setup with AR8327, but there are several examples
> for AR8316, e.g. the RouterStation Pro [1].
>
> The switch driver claiming phy 0 is technically wrong, as the
> connection to the switch isn't using phy 0, but uses a fixed (R)(G)MII
> connection that does not support autonegotiation. But there also is no
> other phy address on the MDIO bus which represents the cpu port, so we
> need this workaround for autodetection/-attachment.
>
> From the switch perspective port 0 / cpu port. Phy 0 actually belongs
> to the external port 1, therefore we stub it out for addr == 0.
>
>
> Jonas


Thanks a lot for the comprehensive explanation!

Heiner
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