netdev - Re: [PATCH net-next v3 02/10] net: mvpp2: phylink support

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Message-ID: <20180831141123.GM30658@n2100.armlinux.org.uk>
Date:   Fri, 31 Aug 2018 15:11:23 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Antoine Tenart <antoine.tenart@...tlin.com>
Cc:     davem@...emloft.net, kishon@...com, gregory.clement@...tlin.com,
        andrew@...n.ch, jason@...edaemon.net,
        sebastian.hesselbarth@...il.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com,
        maxime.chevallier@...tlin.com, miquel.raynal@...tlin.com,
        nadavh@...vell.com, stefanc@...vell.com, ymarkman@...vell.com,
        mw@...ihalf.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH net-next v3 02/10] net: mvpp2: phylink support

On Fri, Aug 31, 2018 at 03:36:51PM +0200, Antoine Tenart wrote:
> With the above code remove one case did not worked anymore: when the
> port is configured as a fixed-link because the SFP cage can't be
> described and used (on the 7040-db and 8040-db boards). In such cases
> phylink is called, mac_config() is called, but link_up() is never
> called. I'm not sure this is actually an issue in phylink, but the PPv2
> driver should probably take care of this weird case itself (by calling
> explicitly link_up()). What do you think?

Fixed link should work:

- when a fixed link is configured, link_config.link is set true.
- when phylink_start() is called, mac_config() will be called to do the
  initial setup, and a resolve is triggered.
- phylink_resolve() will read the fixed link state, which in the case
  of no GPIO, will inherit link_config.link.
  - you will then see another mac_config() call.

Now what happens depends whether you've set the netdev's carrier state
in the driver - if you haven't, the netdev's carrier state should be
off.  Since the state mismatches the link_state.link (which will be
true), you will get a mac_link_up() call.

mvneta ensures this state by always calling netif_carrier_off() in
mvneta_open(), maybe that ought to be in phylink_start() as that's the
state that phylink expects when phylink_start() has been called.  So,
maybe it's a phylink bug.

Can you see any down-sides to moving the netif_carrier_off() in
mvneta_open() to phylink_start() ?

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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