Merge branch 'rmnet-tx-pkt-aggregation'

Daniele Palmas says:

====================
net: add tx packets aggregation to ethtool and rmnet

Hello maintainers and all,

this patchset implements tx qmap packets aggregation in rmnet and generic
ethtool support for that.

Some low-cat Thread-x based modems are not capable of properly reaching the maximum
allowed throughput both in tx and rx during a bidirectional test if tx packets
aggregation is not enabled.

I verified this problem with rmnet + qmi_wwan by using a MDM9207 Cat. 4 based modem
(50Mbps/150Mbps max throughput). What is actually happening is pictured at
https://drive.google.com/file/d/1gSbozrtd9h0X63i6vdkNpN68d-9sg8f9/view

Testing with iperf TCP, when rx and tx flows are tested singularly there's no issue
in tx and minor issues in rx (not able to reach max throughput). When there are concurrent
tx and rx flows, tx throughput has an huge drop. rx a minor one, but still present.

The same scenario with tx aggregation enabled is pictured at
https://drive.google.com/file/d/1jcVIKNZD7K3lHtwKE5W02mpaloudYYih/view
showing a regular graph.

This issue does not happen with high-cat modems (e.g. SDX20), or at least it
does not happen at the throughputs I'm able to test currently: maybe the same
could happen when moving close to the maximum rates supported by those modems.
Anyway, having the tx aggregation enabled should not hurt.

The first attempt to solve this issue was in qmi_wwan qmap implementation,
see the discussion at https://lore.kernel.org/netdev/20221019132503.6783-1-dnlplm@gmail.com/

However, it turned out that rmnet was a better candidate for the implementation.

Moreover, Greg and Jakub suggested also to use ethtool for the configuration:
not sure if I got their advice right, but this patchset add also generic ethtool
support for tx aggregation.

The patches have been tested mainly against an MDM9207 based modem through USB
and SDX55 through PCI (MHI).

v2 should address the comments highlighted in the review: the implementation is
still in rmnet, due to Subash's request of keeping tx aggregation there.

v3 fixes ethtool-netlink.rst content out of table bounds and a W=1 build warning
for patch 2.

v4 solves a race related to egress_agg_params.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

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