Hi Russell,

On Mon, Mar 19, 2018 at 11:12:05AM +0000, Russell King - ARM Linux wrote:

On Mon, Mar 19, 2018 at 09:52:52AM +0100, Antoine Tenart wrote:

quoted

Anyway, the reason to use in-band negotiation was also to avoid using
fixed-link. It would work but always report the link is up, which for
the user isn't a great experience as we have a way to detect this.

What would you suggest to achieve this in a reasonable way?

The intention of this test in phylink_of_phy_connect() is to avoid
failing when there is no requirement for a PHY to be present (such as
a fixed link, or an 802.3z link.)  However, with 10G PHYs such as the
3310, we need the PHY so we can read the speed from it, and so know
whether to downgrade the MAC to SGMII mode, or having downgraded the
MAC, upgrade it back to 10G mode when the PHY switches to 10G.

I'm guessing that you're wanting this for the DB boards, but I don't
see why.  Do they not have PHYs?

You guessed right, that's exactly my use case. The DB boards (7k and 8k)
have 10G interfaces without PHYs. I could describe them as fixed-link
(it works), but it would be better not to require a PHY in
phylink_of_phy_connect() for such interfaces.

That's why I used in-band AN, which is wrong, but we still probably
need to add a check to allow such setups. I'm all ears for suggestions
as I do not have the full picture of all the supported modes and their
requirements.

Thanks!
Antoine

-- 
Antoine Ténart, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com