Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

FreeBSD driver does not require arpcom structure in softc.

Consistently use a tab character instead of using either a space or
tab after #define.
While I'm here consistently use capital letters when it uses
hexadecimal notation.

No functional changes.

Implement hardware MAC statistics counter. Counters could be
queried with dev.et.%d.stats sysctl node where %d is an instance of
device.

Rework link state tracking and TX/RX MAC configuration.
o Do not report link status if driver is not running.
o TX/RX MAC configuration should be done with resolved speed,
duplex and flow control after establishing a link so it can't
be done in driver initialization routine.
Move the configuration to miibus_statchg callback which will be
called whenever any link state change is detected.
At this moment, flow-control is not enabled yet mainly because
I was not able to set correct flow control parameters to
generate TX pause frames.
o Now TX/RX MAC is enabled only when a valid link is detected.
Rearragnge hardware initialization routine a bit to leave
enabling MAC to miibus_statchg callback. In order to that,
TX/RX DMA engine is enabled in et_init_locked().
o Introduce ET_FLAG_LINK flag to track current link state.
o Introduce ET_FLAG_FASTETHER flag to mark whether controller is
fast ethernet. This flag is checked in miibus_statchg callback
to know whether PHY established a valid link.
o In et_stop(), TX/RX MAC is explicitly disabled instead of
relying on et_reset(). And move et_reset() from et_stop() to
controller initialization. Controler reset is not required here
and it would also clear critial registers(i.e station address,
RX filter configuration, WOL etc) that are required to make WOL
work.
o Switching to current media is done in et_init_locked() after
setting IFF_DRV_RUNNING flag. This should ensure reliable
auto-negotiation/manual link establishment.
o In et_start_locked(), check whether driver got a valid link
before trying to send frames.
o Remove checking a link in et_tick() as this is done by
miibus_statchg callback.

Controller does not require TX start command for every frame. So
send a single TX command after setting up all TX frames. This
removes unnecessary register accesses and bus_dmamap_sync(9) calls.
et(4) uses TX interrupt moderation so it's possible to have TX
buffers that were already transmitted but waiting for TX completion
interrupt. If the number of available TX descriptor is less then
1/3 of total TX descriptor, try reclaiming first to get enough free
TX descriptors before setting up TX descriptors.
After r228325, et_txeof() no longer tries to send frames after
reclaiming TX buffers. That change was made to give more chance
to transmit frames in main interrupt handler since we can still
send frames in interrupt handler with RX interrupt. So right
before exiting interrupt hander, after enabling interrupt, try to
send more frames. This gives slightly better performance numbers.

While I'm here reduce number of spare TX descriptors from 8 to 4.
Controller does not require reserved TX descriptors, it was just to
reduce TX overhead. After r228325, driver has much lower TX
overhead so it does not make sense to reserve 8 TX descriptors.

Overhaul bus_dma(9) usage in et(4) and clean up TX/RX path. This
change should make et(4) work on any architectures.
o Remove m_getl inline function and replace it with stanard mbuf
interfaces. Previous code tried to minimize code duplication
but this came from incorrect use of common DMA tag.
Driver may be still use a common RX allocation handler with
additional structure changes but I don't see much point to do
that it would make it hard to understand the code.
o Remove DragonflyBSD specific constant EVL_ENCAPLEN, use
ETHER_VLAN_ENCAP_LEN instead.
o Add bunch of new RX status definition. It seems controller
supports RX checksum offloading but I was not able to make the
feature work yet. Currently driver checks whether recevied
frame is good one or not.
o Avoid a typedef ending in '_t' as style(9) says.
o Controller has no restriction on DMA address space, so there
is no reason to limit the DMA address to 32bit. Descriptor
rings, status blocks and TX/RX buffers now use full 64bit DMA
addressing.
o Allocate DMA memory shared between host and controller as
coherent.
o Create 3 separate DMA tags to be used as TX, mini RX ring and
stanard RX ring. Previously it created a single DMA tag and it
was used to all three rings.
o et(4) does not support jumbo frame at this moment and I still
don't quite understand how jumbo frame works on this controller
so use two RX rings to handle small sized frame and normal sized
frame respectively. The mini RX ring will be used to receive
frames that are less than or equal to 127 bytes. The second RX
ring is used to receive frames that are not handled by the first
RX ring.
If jumbo frame support is implemented, driver may have to choose
better RX scheme by letting the second RX ring handle jumbo
frames. This scheme will mimic Broadcom's efficient jumbo frame
handling feature. However RAM buffer size(16KB) of the
controller is too small to hold 2 jumbo frames, if 9KB
jumbo frame is used, I'm not sure how good performance would it
have.
o In et_rxeof(), make sure to check whether controller received
good frame or not. Passing corrupted frame to upper layer is
bad idea.
o If driver receives a bad frame or driver fails to allocate RX
buffer due to resource shortage condition, reuse previously
loaded DMA map for RX buffer instead of unloading/loading RX
buffer again.
o et_init_tx_ring() never fails so change return type to void.
o In watchdog handler, show TX DMA write back status of errored
frame which could be used as a clue to debug watchdog timeout.
o Add missing bus_dmamap_sync() in various places such that et(4)
should work with bounce buffers(e.g. PAE).
o TX side bus_dmamap_load_mbuf_sg(9) support.
o RX side bus_dmamap_load_mbuf_sg(9) support.
o Controller has no DMA alignment limit in RX buffer so use
m_adj(9) in RX buffer allocation to make IP header align on 2
bytes boundary. Otherwise it would trigger unaligned access
error in upper layer on strict alignment architectures.
One of down side of controller is it provides limited set of RX
buffer length like most Intel controllers. This is not problem
at this moment because driver does not support jumbo frame yet
but it may require alignment fixup code to support jumbo frame
on strict alignment architectures.
o In et_txeof(), don't zero TX descriptors for transmitted frames.
TX descriptors don't need write access after transmission.
Driver sets IFF_DRV_OACTIVE when the number of available TX
descriptors are less than or equal to ET_NSEG_SPARE. Make sure
to clear IFF_DRV_OACTIVE only when the number of available TX
descriptor is greater than ET_NSEG_SPARE.

Change copyright holder to author. We prefer using a real legal
entity for copyright holders.

Approved by: sephe
MFC after: 3 days

Add IPv4/TCP/UDP Tx checksum offloading support. It seems the
controller also has support for IP/TCP checksum offloading for Rx
path. But I failed to find to way to enable Rx MAC to compute the
checksum of received frames.

Remove unnecessary structure packing.

Use bus_{read,write}_4 rather than bus_space_{read,write}_4.

Remove extra spce at the EOL.

Add MSI support.

Remove complex macros that were used to compute bits values.
Although these macros may have its own strength, its complex
definition make hard to read the code.

Approved by: delphij

Add et(4), a port of DragonFly's Agere ET1310 10/100/Gigabit
Ethernet device driver, written by sephe@

Obtained from: DragonFly
Sponsored by: iXsystems
MFC after: 2 weeks