Merge branch 'stmmac-optimizations'

Alexandre TORGUE says:

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stmmac: enhance driver performances and update the version

According to Giuseppe, I send the v3 series.

This is a subset of patches to rework the driver in order to improve its
performances and make it more robust under stress conditions.

All patches have been ported on STi mainstream kernel branch and
tested on ARM STiH4xx platforms and newer ones.

This series also updates the driver version and prepares it
to include further development to support new chips.

In detail, these patches are:

o to rework and improve the internal DMA bus settings

  Fine tuning is mandatory on some platforms for both
  performance and stability issues.

o to rework and optimize the descriptor management.

  This will help a lot on performance side and preparing
  the inclusion on the GMAC4.x.

o to add a set of optimizations for both xmit and rx functions.

  These will help a lot on performance side and making the driver
  more robust in case of low memory conditions and under some
  stress test, performed for example on IP-STB.

Below some throughput figures obtained on some boxes before and after
the patches.

                       nuttcp (mbps)       iperf (Mbps)
------------------------------------------------------------------
                      tcp     udp          tcp      udp
                   tx   rx   tx  rx      tx   rx   tx  rx
                    ------------------------------------------
   old             680   800 480  506    760  800   600  700
   new             830   880 540  630    840  880   700   800

V2: - rx_copybreak is now managed by using ethtool.
V3: - improve comments on PCIe detailing that there are no regressions
    - rework some APIs to properly define some params as bool as expected
    - rework the formula to get the element inside the ring. Comparing V2,
	patches 4 and 13 have been merged because the same formula have been
	used. After this rework, no evident benefit has been noticed in terms
	of performances so the table above is still valid. Disassembling the
	code for SH4 and ARM, with the new formula just an instr is saved
	(depending on compiler flags) and this gives us not so relevanti gain,
	for example, on SH4 where some instr are executed in the same pipeline
	stage.
	Ring sizes are now fixed and maybe they can be reworked to be tuned
	w/o using stmmaceth= cmdline option. Indeed, nobody change these sizes
	and indeed the numbers selected by default respect the budget and
	avoid to pass invalid setup. These are the best driver default sizes
	for ring and chain.

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