Re: [PATCH 4/6] of: add API for changing parameters of fixed link

30.03.2015 19:06, Florian Fainelli пишет:

2015-03-30 7:39 GMT-07:00 Stas Sergeev [off-list ref]:

quoted

27.03.2015 20:15, Florian Fainelli пишет:

quoted

I think your concerns are valid, but I don't think there is going to be
any problem with the approach I suggested because there is a contract
that the fixed PHYs and regular PHYs need to

Hello Florian.

As promised, today I tried to resurrect my first implementation
and do things as you suggested: install the link_update callback
for mvneta privately.
I feel SGMII setup is very common and deserves the separate API,
not the per-driver handling, but in any case, I'd like to show
the implementation first, then discuss.

Unfortunately, it didn't work quite right.
The problem is that mvneta calls phy_disconnect() on .ndo_stop
callback. After that, phy->attached_dev becomes NULL, and so the
link_update callback gets called with net_dev==NULL! And crashs.
Of course I can easily work around that, but IMHO its a bug -
the one that actually gets fixed by the patches I posted previously.

I actually submitted some patches a while ago that allow you to
unregister the fixed_link_update callback before in case you need to,
precisely for that. Since this is specific to dealing with a fixed
PHY, it is the driver responsibility to know that is has registered a
fixed_link_update callback and then unregister it by passing a NULL
callback as the new callback.

Today I posted the patch that does exactly that.
But I already see the problem:
---
[   10.535424] mvneta f1030000.ethernet eth1: Link is Up - Unsupported (update phy.c)/Half - flow control off
---

Seems like if I register a callback after of_phy_connect()
(and unregister before disconnect), there is a small window
between connect and setting the callback. If someone at that
time will query phy, he'll get an undefined status (speed).
And before of_phy_connect() the phy_device pointer is not known
to register callback earlier. Of course I can see the possible
work-arounds, but I wonder if something better can be done
than using of_phy_find_device() and related magic right before
of_phy_connect() just for that.