Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Don't expose the uart_ops structure directly, but instead have
it obtained through the uart_class structure. This allows us
to declare the uart_class structure as weak and as such allows
us to reference it even when it's not compiled-in.
It also allows is to get the uart_ops structure by name, which
makes it possible to implement the dt tag handling in uart_getenv().
The side-effect of all this is that we're using the uart_class
structure more consistently which means that we now also have
access to the size of the bus space block needed by the hardware
when we map the bus space, eliminating any hardcoding.

- Add a uart_rxready() and corresponding device-specific implementations
that can be used to check whether receive data is ready, i.e. whether
the subsequent call of uart_poll() should return a char, and unlike
uart_poll() doesn't actually receive data.
- Remove the device-specific implementations of uart_poll() and implement
uart_poll() in terms of uart_getc() and the newly added uart_rxready()
in order to minimize code duplication.
- In sunkbd(4) take advantage of uart_rxready() and use it to implement
the polled mode part of sunkbd_check() so we don't need to buffer a
potentially read char in the softc.
- Fix some mis-indentation in sunkbd_read_char().

Discussed with: marcel

Don't hold the hardware mutex across getc(). It can wait indefinitely
for a character to be received. Instead let getc() do any necesary
locking.

Add support for scc(4).

Start each of the license/copyright comments with /*-, minor shuffle of lines

Remove the whole uart_cpu_identify() stuff again. Now that it's no longer
used on sparc64 they are only stubs on all architectures and it doesn't
look like if we would need it in the near future again.

Ok'ed by: marcel

- Introduce an uart_cpu_identify() which is implemented in uart_cpu_<arch>.c
and that can be used as an identify function for all kinds of busses on a
certain platform. Expect for sparc64 these are only stubs right now. [1]
- For sparc64, add code to its uart_cpu_identify() for registering the on-
board ISA UARTs and their resources based on information obtained from
Open Firmware.
It would be better if this would be done in the OFW ISA code. However, due
to the common FreeBSD ISA code and PNP-IDs not always being present in the
properties of the ISA nodes there seems to be no good way to implement that.
Therefore special casing UARTs as the sole really relevant ISA devices on
sparc64 seemed reasonable. [2]

Approved by: marcel
Discussed with: marcel [1], tmm [2]
Tested by: make universe

Introduce the hw.uart.console and hw.uart.dbgport environment variables
to select a serial console and debug port (resp). On ia64 these replace
the use of hints completely and take precedence over hints on alpha,
amd64 and i386. On sparc64 these variables are not yet recognised.

The reasons for introducing these variables are:
1. Hints have side-effects. They reserve the unit number for use by
isa or acpi devices and therefore cannot be used to select a pci
device. Also, the use of a unit number to select a device prior
to bus enumeration is nonsense. The new variables have no side-
effects and are not based on unit numbers.
2. Hints don't have the expression power to allow the sysadmin to
select UARTs that are not legacy PC devices and need the support
of compile-time constants to give the sysadmin some level of
flexibility.

The hw.uart.console and hw.uart.dbgport variables specify a list of
attributes. An attribute is a tag-value pair, seperated by a colon.
Attributes are seperated by a comma. Where possible, tags are the
same as those in /etc/remote (only br and pa in practice). Details
can be found in the manpage (not part of this commit).

Not tested on: amd64, pc98

- Keep the base address in struct uart_bas for sab82532 and z8530 modules.
- Remove buggy uart_cpu_busaddr() function.

Remove the assumption that a bus_space_handle_t is an I/O address
from the SAB82532 and the Z8530 hardware drivers by introducing
uart_cpu_busaddr(). The assumption is not true on pc98 where
bus_space_handle_t is a pointer to a structure.
The uart_cpu_busaddr() function will return the bus address
corresponding the tag and handle given to it by the BAS.

WARNING: the intend of the function is STRICTLY to allow hardware
drivers to determine which logical channel they control and is NOT
to be used for actual I/O. It is therefore EXPLICITLY allowed that
uart_cpu_busaddr() returns only the lower 8 bits of the address
and garbage in all other bits. No mistakes...

Better stab at MD code for pc98. The 8251 stuff is a total lie
(ns8250 copied and s/ns8250/i8251/g), but there for linkage purposes.
Real code to follow, once I get past some boot issues on my pc98 boxes
with recent current.

The uart(4) driver is an universal driver for various UART hardware.
It improves on sio(4) in the following areas:
o Fully newbusified to allow for memory mapped I/O. This is a must
for ia64 and sparc64,
o Machine dependent code to take full advantage of machine and firm-
ware specific ways to define serial consoles and/or debug ports.
o Hardware abstraction layer to allow the driver to be used with
various UARTs, such as the well-known ns8250 family of UARTs, the
Siemens sab82532 or the Zilog Z8530. This is especially important
for pc98 and sparc64 where it's common to have different UARTs,
o The notion of system devices to unkludge low-level consoles and
remote gdb ports and provides the mechanics necessary to support
the keyboard on sparc64 (which is UART based).
o The notion of a kernel interface so that a UART can be tied to
something other than the well-known TTY interface. This is needed
on sparc64 to present the user with a device and ioctl handling
suitable for a keyboard, but also allows us to cleanly hide an
UART when used as a debug port.

Following is a list of features and bugs/flaws specific to the ns8250
family of UARTs as compared to their support in sio(4):
o The uart(4) driver determines the FIFO size and automaticly takes
advantages of larger FIFOs and/or additional features. Note that
since I don't have sufficient access to 16[679]5x UARTs, hardware
flow control has not been enabled. This is almost trivial to do,
provided one can test. The downside of this is that broken UARTs
are more likely to not work correctly with uart(4). The need for
tunables or knobs may be large enough to warrant their creation.
o The uart(4) driver does not share the same bumpy history as sio(4)
and will therefore not provide the necessary hooks, tweaks, quirks
or work-arounds to deal with once common hardware. To that extend,
uart(4) supports a subset of the UARTs that sio(4) supports. The
question before us is whether the subset is sufficient for current
hardware.
o There is no support for multiport UARTs in uart(4). The decision
behind this is that uart(4) deals with one EIA RS232-C interface.
Packaging of multiple interfaces in a single chip or on a single
expansion board is beyond the scope of uart(4) and is now mostly
left for puc(4) to deal with. Lack of hardware made it impossible
to actually implement such a dependency other than is present for
the dual channel SAB82532 and Z8350 SCCs.

The current list of missing features is:
o No configuration capabilities. A set of tunables and sysctls is
being worked out. There are likely not going to be any or much
compile-time knobs. Such configuration does not fit well with
current hardware.
o No support for the PPS API. This is partly dependent on the
ability to configure uart(4) and partly dependent on having
sufficient information to implement it properly.

As usual, the manpage is present but lacks the attention the
software has gotten.