Merge branch 'stmmac-GMAC4.x'

Alexandre TORGUE says:

====================
Enhance stmmac driver to support GMAC4.x IP

This is a subset of patch to enhance current stmmac driver to support
new GMAC4.x chips. New set of callbacks is defined to support this new
family: descriptors, dma, core.

One of main changes of GMAC 4.xx IP is descriptors management.
 -descriptors are only used in ring mode.
 -A descriptor is composed of 4 32bits registers (no more extended
  descriptors)
 -descriptor mechanism (Tx for example, but it is exactly the same for RX):
 -useful registers:
  -DMA_CH#_TxDesc_Ring_Len: length of transmit descriptor ring
  -DMA_CH#_TxDesc_List_Address: start address of the ring
  -DMA_CH#_TxDesc_Tail_Pointer: address of the last descriptor to send + 1.
  -DMA_CH#_TxDesc_Current_App_TxDesc: address of the current descriptor

 -The descriptor Tail Pointer register contains the pointer to the
  descriptor address (N). The base address and the current
  descriptor decide the address of the current descriptor that the
  DMA can process. The descriptors up to one location less than the
  one indicated by the descriptor tail pointer (N-1) are owned by
  the DMA. The DMA continues to process the descriptors until the
  following condition occurs:
  "current descriptor pointer == Descriptor Tail pointer"

  Then the DMA goes into suspend mode. The application must perform
  a write to descriptor tail pointer register and update the tail
  pointer to have the following condition and to start a new transfer:
  "current descriptor pointer < Descriptor tail pointer"

  The DMA automatically wraps around the base address when the end
  of ring is reached.

New features are available on IP:
 -TSO (TCP Segmentation Offload) for TX only
 -Split header: to have header and payload in 2 different buffers (not yet implemented)

Below some throughput figures obtained on some boxes:

                        iperf (mbps)
--------------------------------------
                       tcp     udp
                    tx   rx   tx  rx
                     -----------------
    GMAC4.x         935  930  750 800

Note: There is a change in 4.10a databook on bitfield mapping of DMA_CHANx_INTR_ENA register.
This requires to have é diffrent set of callbacks between IP 4.00a and 4.10a.
====================

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

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