Hi Russell,

On Fri, Aug 31, 2018 at 03:11:23PM +0100, Russell King - ARM Linux wrote:

On Fri, Aug 31, 2018 at 03:36:51PM +0200, Antoine Tenart wrote:

quoted

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.

OK, that makes sense. Thanks for the explanations.

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() ?

I removed most of my previous fix, and called netif_carrier_off() just
before phylink_start() in PPv2. I worked, and it seemed to me all cases
were working fine.

As calling netif_carrier_off() seems to be a phylink assumption, I would
agree to call it directly from within phylink_start(). But I don't have
the full picture here.

If such a solution is OK for you, and if no one raises an issue in the
next days, I can send a series to add a netif_carrier_off() call, fix
PPv2, and remove mvneta's call to netif_carrier_off() in mvneta_open().

Thanks!
Antoine

-- 
Antoine T?nart, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com