Merge branch 'ethtool-allow-nesting-of-begin-and-complete-callbacks'

Michal Kubecek says:

====================
ethtool: allow nesting of begin() and complete() callbacks

The ethtool ioctl interface used to guarantee that ethtool_ops callbacks
were always called in a block between calls to ->begin() and ->complete()
(if these are defined) and that this whole block was executed with RTNL
lock held:

	rtnl_lock();
	ops->begin();
	/* other ethtool_ops calls */
	ops->complete();
	rtnl_unlock();

This prevented any nesting or crossing of the begin-complete blocks.
However, this is no longer guaranteed even for ioctl interface as at least
ethtool_phys_id() releases RTNL lock while waiting for a timer. With the
introduction of netlink ethtool interface, the begin-complete pairs are
naturally nested e.g. when a request triggers a netlink notification.

Fortunately, only minority of networking drivers implements begin() and
complete() callbacks and most of those that do, fall into three groups:

  - wrappers for pm_runtime_get_sync() and pm_runtime_put()
  - wrappers for clk_prepare_enable() and clk_disable_unprepare()
  - begin() checks netif_running() (fails if false), no complete()

First two have their own refcounting, third is safe w.r.t. nesting of the
blocks.

Only three in-tree networking drivers need an update to deal with nesting
of begin() and complete() calls: via-velocity and epic100 perform resume
and suspend on their own and wil6210 completely serializes the calls using
its own mutex (which would lead to a deadlock if a request request
triggered a netlink notification). The series addresses these problems.

changes between v1 and v2:
  - fix inverted condition in epic100 ethtool_begin() (thanks to Andrew
    Lunn)
====================

Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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