axgbe: fix some link related issues

By default, axgbe driver does a receiver reset after predefined number
of retries for the link to come up. However, this receiver reset
doesn't always suffice, du

axgbe: fix some link related issues

By default, axgbe driver does a receiver reset after predefined number
of retries for the link to come up. However, this receiver reset
doesn't always suffice, due to an hardware issue.
In that case, as a workaround, a complete phy reset is necessary.
This patch introduces a sysctl that can be set to 1 to let the driver
reset the phy completely, rather than just doing receiver reset.
The workaround will be removed once the issue is fixed by means
of firmware update.

This patch also fixes the handling of the direct attach cables
properly.

Submitted by: rajesh1.kumar_amd.com
Differential Revision: https://reviews.freebsd.org/D28266

(cherry picked from commit bfd75d45571958398a043517060d8c3d352e7dbd)

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axgbe: driver changes for netmap support

AMD 10GbE hardware is designed to have two buffers per receive descriptor to
support split header feature. For this purpose, the driver was designed to use
2

axgbe: driver changes for netmap support

AMD 10GbE hardware is designed to have two buffers per receive descriptor to
support split header feature. For this purpose, the driver was designed to use
2 iflib freelists per receive queue. So, that buffers from 2 freelists are used
to refill an entry in the receive descriptor. The current design holds good
with regular data traffic.

But, when netmap comes into play, the current design will not fit in. The
current netmap interfaces and netmap implementation in iflib doesn't seem
to accomodate the design of 2 freelists per receive queue. So, exercising
Netmap capability with inbuilt tools like bridge, pkt-gen doesn't work with
the 2 freelists driver design.

So, the driver design is changed to accomodate the current netmap interfaces
and netmap implementation in iflib by using single freelist per receive queue
approach when Netmap capability is exercised without disturbing the current
2 freelists approach.
The dev.ax.sph_enable tunable can be set to 0 to configure the single
free list mode.

Thanks to Stephan Dewt for his Initial set of code changes for the stated
problem.

Submitted by: rajesh1.kumar_amd.com
Approved by: vmaffione
MFC after: 3 weeks
Differential Revision: https://reviews.freebsd.org/D27797

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