[Midnightbsd-cvs] src: sys/pci: Overhaul re(4).

[laffer1 at midnightbsd.org]

Log Message:
-----------
 Overhaul re(4).
  o Increased number of Rx/Tx descriptors to 256 for 8169 GigEs
    because it's hard to push the hardware to the limit with default
    64 descriptors.
    TSO requires large number of Tx descriptors to pass a full sized
    TCP segment(65535 bytes IP packet) to hardware. Previously it
    consumed 32 Tx descriptors, assuming MCLBYTES DMA segment size,
    to send the TCP segment which means re(4) couldn't queue more
    than two full sized IP packets.
    For 8139C+ it still uses 64 Rx/Tx descriptors due to its hardware
    limitations. With this changes there are (very) small waste of
    memory for 8139C+ users but I don't think it would affect 8139C+
    users for most cases.
  o Various bus_dma(9) fixes.
     - The hardware supports DAC so allow 64bit DMA operations.
     - Removed BUS_DMA_ALLOC_NOW flag.
     - Increased DMA segment size to 4096 from MCLBYTES because TSO
       consumes too many descriptors with MCLBYTES DMA segment size.
     - Tx/Rx side bus_dmamap_load_mbuf_sg(9) support. With these
       changes the code is more readable than previous one and got a
       (slightly) better performance as it doesn't need to pass/
       decode arguments to/from callback function.
     - Removed unnecessary callback function re_dmamap_desc() and
       nuked rl_dmaload_arg structure which was used in the callback.
     - Additional protection for DMA map load failure. In case of
       failure reuse current map instead of returning a bogus DMA
       map.
    -  Deferred DMA map unloading/sync operation for maximum
       performance until we really need to load new DMA map. If we
       happen to reuse current map(e.g. input error) there is no need
       to sync/unload/load again.
    -  The number of allowable Tx DMA segments for a mbuf chains are
       now 32 instead of magic nseg value. If the number of available
       Tx descriptors are short enough to send highly fragmented mbuf
       chains an optimized re_defrag() is called to collapse mbuf
       chains which is supposed to be much faster than m_defrag(9).
       re_defrag() was borrowed from ath(4).
     - Separated Rx/Tx DMA tag from a common DMA tag such that Rx DMA
       tag correctly uses DMA maps that were created with DMA alignment
       restriction(8bytes alignments). Tx DMA tag does not have such
       alignment limitation.
     - Added additional sanity checks for DMA ring map load failure.
     - Added additional spare Rx DMA map for graceful handling of Rx
       DMA map load failure.
     - Fixed misused bus_dmamap_sync(9) and added missing
       bus_dmamap_sync(9) in re_encap()/re_txeof()/re_rxeof().
  o Enabled TSO again as re(4) have reasonable number of Tx
    descriptors.
  o Don't touch DMA address of a Tx descriptor in re_txeof(). It's
    not needed.
  o Fix incorrect update of if_ierrors counter. For Rx buffer
    shortage it should update if_qdrops as the buffer is reused.
  o Added checks for unsupported H/W revisions and return ENXIO for
    these hardwares. This is required to remove resource allocation
    code in re_probe as other drivers do in device probe routine.
  o Modified descriptor index manipulation macros as it's now possible
    to have different number of descriptors for Rx/Tx.
  o In re_start, to save a lock operation, use IFQ_DRV_IS_EMPTY before
    trying to invoke IFQ_DRV_DEQUEUE. Also don't blindly call re_encap
    since we already know the number of available Tx descriptors in
    advance.
  o Removed RL_TX_DESC_THLD which was used to reserve RL_TX_DESC_THLD
    descriptors in Tx path. There is no such a limitation mentioned in
    8139C+/8169/8110/8168/8101/8111 datasheet and it seems to work ok
    without reserving RL_TX_DESC_THLD descriptors.
  o Fix a comment for RL_GTXSTART. The register is 8bits register.
  o Added comments for 8169/8139C+ hardware restrictions on descriptors.
  o Removed forward declaration for "struct rl_softc", it's not needed.
  o Added a new structure rl_txdesc for Tx descriptor managements and
    a structure rl_rxdesc for Rx descriptor managements.
  o Removed unused member variable rl_intlock in driver softc. There are
    still several unused member variables which are supposed to be used
    to access hardware statistics counters. But it seems that accessing
    hardware counters were not implemented yet.

Obtained from: FreeBSD , RELENG_7 if_re.c 1.101, if_re.c 1.102, if_rlreg.h 1.70

Modified Files:
--------------
    src/sys/pci:
        if_rlreg.h (r1.5 -> r1.6)
        (http://cvsweb.midnightbsd.org/src/sys/pci/if_rlreg.h?r1=1.5&r2=1.6)
    src/sys/dev/re:
        if_re.c (r1.7 -> r1.8)
        (http://cvsweb.midnightbsd.org/src/sys/dev/re/if_re.c?r1=1.7&r2=1.8)