Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

o Revamp the sparc64 interrupt code in order to be able to interface
with the INTR_FILTER-enabled MI code. Basically this consists of
registering an interrupt controller (of which there can be multiple
and optionally different ones either per host-to-foo bridge or shared
amongst host-to-foo bridges in any one machine) along with an interrupt
vector as specific argument for all the interrupt vectors used by a
given host-to-foo bridge (roughly similar to registering interrupt
sources on amd64 and i386), providing functions to enable, clear and
disable the interrupts of the children beneath the bridge.
This also includes:
- No longer entering a critical section in tl0_intr() and tl1_intr()
for executing interrupt handlers but rather let the handlers enter
it themselves so in the case of intr_event_handle() we don't enter
a nested critical section.
- Adding infrastructure for binding delivery of interrupt vectors to
specific CPUs which later on can be interfaced with the code from
amd64/i386 for binding interrupts to specific CPUs.
- Getting rid of the wrapper hack introduced along the lines of the
API changes for INTR_FILTER which as a side-effect caused interrupts
associated with ithread handlers only to get the elevated priority
of those associated with filters ("fast handlers") (this removes the
hack also in the non-INTR_FILTER case).
- Disabling (by not clearing) an interrupt in the interrupt controller
until all associated handlers have been executed, which is crucial
for the typical locking strategy of NIC drivers in order to work
correctly in case of shared interrupts. This was a more or less
theoretical problem on sparc64 though, as shared interrupts are
rather uncommon there except for the on-board SCCs and UARTs.
Note that due to the behavior of at least of some of the interrupt
controllers used on sparc64 an enable+EOI instead of a disable+EOI
approach (as implied by the INTR_FILTER MI code and implemented on
other architectures) is used as the latter can cause lost interrupts
or in the worst case interrupt starvation.
o Correct a typo in sbus_alloc_resource() which caused (pass-through)
allocations to only work down to the grandchildren of the bus, which
wasn't a real problem so far as we don't support any devices which are
great-grandchildren or greater of a U2S bridge, yet.
o In fhc(4) use bus_{read,write}_4() instead of bus_space_{read,write}_4()
in order to get rid of sc_bh and sc_bt in the fhc_softc. Also get rid
of some other unneeded members in fhc_softc.

Reviewed by: marcel (earlier version)
Approved by: re (kensmith)

- Divorce the IOTSBs, which so far where handled via a global list
instead of per IOMMU, so we no longer need to program all of them
identically in systems having multiple IOMMUs. This continues the
rototilling of the nexus(4) done about 5 months ago, which amongst
others changed nexus(4) and the drivers for host-to-foo bridges
to provide bus_get_dma_tag methods, allowing to handle DMA tags in
a hierarchical way and to link them with devices.
This still doesn't move the silicon bug workarounds for Sabre (and
in the uncommitted schizo(4) for Tomatillo) bridges into special
bus_dma_tag_create() and bus_dmamap_sync() methods though, as w/o
fully newbus'ified bus_dma_tag_create() and bus_dma_tag_destroy()
this still requires too much hackery, i.e. per-child parent DMA
tags in the parent driver.
- Let the host-to-foo drivers supply the maximum physical address
of the IOMMU accompanying the bridges. Previously iommu(4) hard-
coded an upper limit of 16GB, which actually only applies to the
IOMMUs of the Hummingbird and Sabre bridges. The Psycho variants
as well as the U2S in fact can can translate to up to 2TB, i.e.
translate to 41-bit physical addresses. According to the recently
available Tomatillo documentation these bridges even translate to
43-bit physical addresses and hints at the Schizo bridges doing
43 bits as well.
This fixes the issue the FreeBSD 6.0 todo list item "Max RAM on
sparc64" was refering to and pretty much obsoletes the lack of
support for bounce buffers on sparc64.

Thanks to Nathan Whitehorn for pointing me at the Tomatillo manual.

Approved by: re (kensmith)

/* -> /*- for license, minor formatting changes

Add support for the SBus, which is used in early Sun UltraSPARC machines.
Ported from NetBSD.