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
as we have no use for that info. Instead let this function return the
keyboard ID and verify at its invocation in sunkbd_configure() that we're
talking to a Sun type 4/5/6 keyboard, i.e. a keyboard supported by this
driver.
- Add an option SUNKBD_EMULATE_ATKBD whose code is based on the respective
code in ukbd(4) and like UKBD_EMULATE_ATSCANCODE causes this driver to
emit AT keyboard/KB_101 compatible scan codes in K_RAW mode as assumed by
kbdmux(4). Unlike UKBD_EMULATE_ATSCANCODE, SUNKBD_EMULATE_ATKBD also
triggers the use of AT keyboard maps and thus allows to use the map files
in share/syscons/keymaps with this driver at the cost of an additional
translation (in ukbd(4) this just is the way of operation).
- Implement an option SUNKBD_DFLT_KEYMAP, which like the equivalent options
of the other keyboard drivers allows to specify the default in-kernel
keyboard map. For obvious reasons this made to only work when also using
SUNKBD_EMULATE_ATKBD.
- Implement sunkbd_check(), sunkbd_check_char() and sunkbd_clear_state(),
which are also required for interoperability with kbdmux(4).
- Implement K_CODE mode and FreeBSD keypad compose.
- As a minor hack define KBD_DFLT_KEYMAP also in the !SUNKBD_EMULATE_ATKBD
case so we can obtain fkey_tab from <dev/kbd/kbdtables.h> rather than
having to duplicate it and #ifdef some more code.
- Don't use the TX-buffer for writing the two command bytes for setting the
keyboard LEDs as this consequently requires a hardware FIFO that is at
least two bytes in depth, which the NMOS-variant of the Zilog SCCs doesn't
have. Thus use an inlined version of uart_putc() to consecutively write
the command bytes (a cleaner approach would be to do this via the soft
interrupt handler but that variant wouldn't work while in ddb(4)). [1]
- Fix some minor style(9) bugs.
PR: 90316 [1]
Reviewed by: marcel [1]
ioctls passing integer arguments should use the _IOWINT() macro.
This fixes a lot of ioctl's not working on sparc64, most notable
being keyboard/syscons ioctls.
Full ABI compatibility is provided, with the bonus of fixing the
handling of old ioctls on sparc64.
Reviewed by: bde (with contributions)
Tested by: emax, marius
MFC after: 1 week
- Rename REG_DL to REG_DLL and REG_DLH.
- Always treat DLL and DLH as two separate 8-bit registers instead of one
16-bit register.
Additionally, remove the probe for the high 4 bits of IER being 0 and don't
assume we can always read/write 0 to/from those bits.
These changes allow uart(4) to drive the UARTs on the Intel XScale PXA255.
Reviewed by: marcel
divisor. This allows us to set the line speed to the maximum
of 1/4 of the device clock.
o Disable the baudrate generator before programming the line
settings, including baudrate, and enable it afterwards.
o Properly use rman(9) to manage resources. This eliminates the
need to puc-specific hacks to rman. It also allows devinfo(8)
to be used to find out the specific assignment of resources to
serial/parallel ports.
o Compress the PCI device "database" by optimizing for the common
case and to use a procedural interface to handle the exceptions.
The procedural interface also generalizes the need to setup the
hardware (program chipsets, program clock frequencies).
o Eliminate the need for PUC_FASTINTR. Serdev devices are fast by
default and non-serdev devices are handled by the bus.
o Use the serdev I/F to collect interrupt status and to handle
interrupts across ports in priority order.
o Sync the PCI device configuration to include devices found in
NetBSD and not yet merged to FreeBSD.
o Add support for Quatech 2, 4 and 8 port UARTs.
o Add support for a couple dozen Timedia serial cards as found
in Linux.
the NS8250 class driver. The UART has FIFOs if sc_rxfifosz>1, so
test for that instead.
While here properly initialize sc_rxfifosz and sc_txfifosz in the
case the UART doesn't have FIFOs.
controllers typically have multiple channels and support a number
of serial communications protocols. The scc(4) driver is itself
an umbrella driver that delegates the control over each channel
and mode to a subordinate driver (like uart(4)).
The scc(4) driver supports the Siemens SAB 82532 and the Zilog
Z8530 and replaces puc(4) for these devices.
interrupt handlers rather than BUS_SETUP_INTR() and BUS_TEARDOWN_INTR().
Uses of the BUS_*() versions in the implementation of foo_intr methods
in bus drivers were not changed. Mostly this just means that some
drivers might start printing diagnostic messages like [FAST] when
appropriate as well as honoring mpsafenet=0.
- Fix two more of the ppbus drivers' identify routines to function
correctly in the mythical case of a machine with more than one ppbus.
Control) devices as console. These are microcontrollers which are either
on-board or part of an add-on card and provide terminal server, remote
power switch and monitoring functionality. For console usage these are
connected to the rest of the system via a SCC or an UART. This commit adds
support for the following variants (corresponds to what 'input-device' and
'output-device' have to be set to):
rsc found on-board in E250 and supposedly some Netra, connected
via a SAB82532, com. parameters can be determined via OFW
rsc-console RSC card found in E280R, Fire V4x0, Fire V8x0, connected
via a NS16550, hardwired to 115200 8N1
lom-console LOMlite2 card found in Netra 20/T4, connected via a NS16550,
hardwired to 9600 8N1
- Add my copyright to uart_cpu_sparc64.c as I've rewritten about one third
of that file over time.
Tested on: E250, E280R
Thanks to: dwhite@ for providing access to an E280R
OK'ed by: marcel
MFC after: 1 week
compilation of kernels without ns8250 support but using the uart framework.
These kernels will be for machines where size matters more, so including code
that can never be executed is undesriable...
o Fix typo in comment
o s/-100/BUS_PROBE_GENERIC/
o s/err/error/ for consistency
o Remove non-applicable comment
o Allow uart_bus_probe() to return the predefined BUS_PROBE_*
contants. In this case: explicitly test for error > 0.
o Oxford Semiconductor PCI Dual Port Serial
o Netmos Nm9845 PCI Bridge with Dual UART
Add PCI IDs for single-port cards:
o Various SIIG Cyber Serial
o Oxford Semiconductor OXCB950 UART
Update description as per puc(4).
and increase flexibility to allow various different approaches to be tried
in the future.
- Split struct ithd up into two pieces. struct intr_event holds the list
of interrupt handlers associated with interrupt sources.
struct intr_thread contains the data relative to an interrupt thread.
Currently we still provide a 1:1 relationship of events to threads
with the exception that events only have an associated thread if there
is at least one threaded interrupt handler attached to the event. This
means that on x86 we no longer have 4 bazillion interrupt threads with
no handlers. It also means that interrupt events with only INTR_FAST
handlers no longer have an associated thread either.
- Renamed struct intrhand to struct intr_handler to follow the struct
intr_foo naming convention. This did require renaming the powerpc
MD struct intr_handler to struct ppc_intr_handler.
- INTR_FAST no longer implies INTR_EXCL on all architectures except for
powerpc. This means that multiple INTR_FAST handlers can attach to the
same interrupt and that INTR_FAST and non-INTR_FAST handlers can attach
to the same interrupt. Sharing INTR_FAST handlers may not always be
desirable, but having sio(4) and uhci(4) fight over an IRQ isn't fun
either. Drivers can always still use INTR_EXCL to ask for an interrupt
exclusively. The way this sharing works is that when an interrupt
comes in, all the INTR_FAST handlers are executed first, and if any
threaded handlers exist, the interrupt thread is scheduled afterwards.
This type of layout also makes it possible to investigate using interrupt
filters ala OS X where the filter determines whether or not its companion
threaded handler should run.
- Aside from the INTR_FAST changes above, the impact on MD interrupt code
is mostly just 's/ithread/intr_event/'.
- A new MI ddb command 'show intrs' walks the list of interrupt events
dumping their state. It also has a '/v' verbose switch which dumps
info about all of the handlers attached to each event.
- We currently don't destroy an interrupt thread when the last threaded
handler is removed because it would suck for things like ppbus(8)'s
braindead behavior. The code is present, though, it is just under
#if 0 for now.
- Move the code to actually execute the threaded handlers for an interrrupt
event into a separate function so that ithread_loop() becomes more
readable. Previously this code was all in the middle of ithread_loop()
and indented halfway across the screen.
- Made struct intr_thread private to kern_intr.c and replaced td_ithd
with a thread private flag TDP_ITHREAD.
- In statclock, check curthread against idlethread directly rather than
curthread's proc against idlethread's proc. (Not really related to intr
changes)
Tested on: alpha, amd64, i386, sparc64
Tested on: arm, ia64 (older version of patch by cognet and marcel)
which serial device to use in that case respectively to not rely on
the OFW names of the input/output and stdin/stdout devices. Instead
check whether input and output refers to the same device and is of
type serial (uart(4) was already doing this) and for the fallback
to a serial console in case a keyboard is the selected input device
but unplugged do the same for stdin and stdout in case the input
device is nonexistent (PS/2 and USB keyboards) or has a 'keyboard'
property (RS232 keyboards). Additionally also check whether the OFW
did a fallback to a serial console in the same way in case the
output device is nonexistent. While at it save on some variables
and for sys/boot/sparc64/loader/metadata.c move the code in question
to a new function md_bootserial() so it can be kept in sync with
uart_cpu_getdev_console() more easily.
This fixes selecting a serial console and the appropriate device
when using a device path for the 'input-device' and 'output-device'
OFW environment variables instead of an alias for the serial device
to use or when using a screen alias that additionally denotes a
video mode (like e.g. 'screen:r1024x768x60') but no keyboard is
plugged in (amongst others). It also makes the code select a serial
console in case the OFW did the same due to a misconfiguration like
both 'input-device' and 'output-device' set to 'keyboard' or to a
nonexisting device (whether the OFW does a fallback to a serial
console in case of a misconfiguration or one ends up with just no
console at all highly depends on the OBP version however).
- Reduce the size of buffers that only ever need to hold the string
'serial' accordingly. Double the size of buffers that may need to
hold a device path as e.g. '/pci@8,700000/ebus@5/serial@1,400000:a'
exceeds 32 chars.
- Remove the package handle of the '/options' node from the argument
list of uart_cpu_getdev_dbgport() as it's unused there and future
use is also unlikely.
MFC after: 1 week
not only means that it's possible (though unlikely) that we hand out
differing tags for the same bus space, it also means that the tags
we handed out are not used during bus enumeration. Both affect our
ability to compare tags. Fix the first by initializing our tags only
once. Fix the second by testing if one of the tags to compare is our
tag and the other is a busspace_isa_{io|mem} tag and declare them
equal if so.
This fixes using uart(4) as the serial console on a ds10. That is,
the low-level console worked, but we could not match the resources
to one of the UARTs found during bus enumeration, which prevented
uart(4) from becoming the console in single- or multi-user mode.
Approved by: re (kensmith)
MFC after: 2 days
Thanks to: all involved in getting a ds10 to me; directly or indirectly.
Special thanks to: Dave Knight, ISC (for not scratching my Porsche :-)
times which was added in the last revision with what should be a proper
solution as long as keyboards that were pluggged in after the kernel
has fully booted aren't supported. I.e. when sunkbd_configure() is
called for the high-level console probe make sure that the keyboard is
both successfully configured (i.e. also probed) and attached. The band-
aid left the possibility to attach the keyboard device to the high-level
console without attaching the keyboard device itself when the keyboard
is plugged in after uart(4) attached but before syscons(4) does.
share their IRQ lines with the i8042. Any IRQ activity (typically during
attach) on the NS16550 used to connect the keyboard when actually the
PS/2 keyboard is selected in OFW causes interaction with the OBP i8042
driver resulting in a hang (and vice versa). As RS232 keyboards and mice
obviously aren't meant to be used in parallel with PS/2 ones on these
boards don't attach to these NS16550 in case the RS232 keyboard isn't
selected in order to prevent such hangs.
Ok'ed by: marcel
UARTs used to connect keyboards and not also PS/2 keyboards and only
return their package handle in case the keyboard is the preferred one
according to the OFW but otherwise still regardless of whether the
keyboard is used for stdin or not. This is simply achieved by looking
at the 'keyboard' alias and returning the corresponding package handle
in case it refers to a SCC/UART. This is change is done in order to
give the keyboard which the OFW or the user selected in OFW on boards
that support additional types of keyboards besides the RS232 ones also
preference in FreeBSD. It will be also used to determine on Sun AXi and
Sun AXmp boards whether a PS/2 or a RS232 is to be used as these are
sort of mutual exclusive there (see upcoming commit to uart_bus_ebus.c).
Note that Tatung AXi boards have the same issue but the former code
happened to already give the PS/2 keyboard preference by not identifying
the respective UART as keyboard system device there because the PS/2
keyboard node precedes the keyboard UART one in the OFW device tree of
these boards (which isn't the case for the Sun AXi).
Ok'ed by: marcel
a band-aid allowing to call this function savely multiple times, e.g.
during sckbdprobe() and sc_probe_unit(). Otherwise calling it a second
time results in a non-working keyboard. This needs a lot of more work
to actually do the right thing and work like expected.
- Let sunkbd_configure() return the number of the found keyboards, i.e.
1 in case probing succeeds, as it's expected. The return values of the
keyboard configure functions however currently aren't checked so this
doesn't make a difference at the moment.
- Use FBSDID.
The core console code checks this field when a console is added and
emits a warning if it's empty. In practice the warning is harmless for
uart(4), because the cn_name is filled in as soon as the device name is
known; which is when the device is enumerated.
To avoid the warning, to avoid possible complications caused by emitting
the warning without there (possibly) being a console selected yet and to
avoid complications when the UART isn't found during bus enumeration, we
just preset the cn_name field here to the name of the driver.
fact that access to RR0 does not need a prior write to the register
index because the index always reverts to 0 after the indexed register
has been accessed.
Typically when a RR or WR is to accessed, one programs the index (which
is a write to the control register), followed by a read or write to the
actual indexed register (a read pr write to the same control register).
When this non-atomic sequence is interrupted after having written the
index and low-level console I/O is done in that situation, the write to
program the index will actually write to the indexed register and nuke
state. This almost always yields a wedge.
By not programming the index register and instead just reading from RR0,
the worst case scenario is non-fatal. For if we don't actually read from
RR0 but some other register we get an invalid status, which may lead us
to conclude that the transit data register is empty when it's not or that
the receive data register contains data when it doesn't. Hence, we may
lose an output character or get a sporadic input character, but given
the situation this is a non-issue.
Full serialization is not possible due to the fact that this code needs
to work from DDB and before mutex initialization has happened.
In collaboration with: kris@, marius@
Tested by: kris@
MFC after: 1 day
X-MFC: 5.4-RELEASE candidate
a serial console anyway because input-device is set to keyboard and
output-device is set to screen but no keyboard is plugged in don't
assume that a device node for the input-device alias exists. While
this is true for RS232 keyboards (the node of the SCC and UART
respectively which controls the keyboard doesn't disappear when no
keyboard is plugged in) this assumption breaks for USB keyboards.
It's most likely also not true for PS/2 keyboards but OFW doesn't
reliably switch to a serial console when the potential keyboard is
a PS/2 one which isn't plugged in so this couldn't be verified
properly.
Reported by: Will Andrews <will@csociety.org>, obrien
MFC after: 1 week
with shared IRQs in case the bus code, MD interrupt code, etc. permits.
Together with sys/sparc64/sparc64/intr_machdep.c rev. 1.21 this fixes
an endless loop in uart_intr() when using the second NS16550 on the ISA
bus of sparc64 machines.
- Destroy the hardware mutex on detach and in case attaching fails.
Approved by: marcel
for nodes hanging off of Central (untested), FireHose (untested) and
PCI (tested) busses.
- Add an additional parameter to OF_decode_addr() which specifies the
index of the register bank to decode.
These should allow to eventually add support for the Z8530 hanging off of
FireHose to uart(4) and to write support for PCI-based graphics adapters.
Suggested by: tmm (back in '03)
The presence or absence of a keyboard does not change whether an
UART is designed as a keyboard port or not and thus whether we
can use the port as a TTY or not.
We now call sunkbd_attach() even when we didn't previously find
a keyboard. Emit a useful message stating that no keyboard was
found, but don't do anything else.
MFC after: 5 days
engineering the pending interrupt sources from the current
state of the controller. For channel A we can always read the
interrupt pending register (RR3). For channel B we can read
the interrupt vector register (RR2) because it contains the
modified vector and thus includes the interrupt source.
Since we currently need puc(4) for the Z8530, we know that
the interrupt handler for both channels will be called and
thus that RR3 will always be read at least once, even if ch A
has no pending interrupt.
NOTE: The modified interrupt vector has no value that represent
a lack of pending interrupt for channel B. That is, the
value read when no interrupts are pending is the same as the
value for the special receive condition. Fortunately, we don't
actually have to depend on that interrupt source. This does
mean that we need to properly handle the overflow condition,
when we read received character from the chip.
o The DSR signal is represented by the SYNC bit in the external
status register (RR0). We now properly track DSR.
o It's save to enable the external/status interrupt source. We
now get interrupts when line signals (DSR, DCD or CTS) change.
Problems fixes:
o interrupt storms.
o blocked open(2).
o lack of (hardware) flow control.
o unable to report DSR.
MFC after: 5 days
the address of a channel on a SCC, it returns 0 on failure. [1]
- Hardcode channel 1 for the keyboard on Z8530, the information present
in the Open Firmware device tree doesn't allow to determine this via
uart_cpu_channel(). This makes the keyboard (if one backs out rev. 1.5
of sys/dev/puc/puc_sbus.c and has both keyboard and mouse plugged in to
avoid the hang that revision works around) and consequently syscons(4)
on Ultra 2 work. There's a problem with the keyboard LEDs similar to
the one on Ultra 60 (LEDs don't get lit under X) though, instead of
lighting just a specific single one all get lit and can't be turned off
again. [1]
- Add comments about what uart_cpu_channel() and uart_cpu_getdev_keyboard()
do and their constraints.
- Improve the comments about what uart_cpu_getdev_[console,dbgport]() do,
they don't return an address (as in bus) but an Open Firmware package
handle.
Reviewed by: marcel (modulo the comments) [1]
- The claim in the commit log of rev. 1.11 of dev/uart/uart_cpu_sparc64.c
etc. that UARTs are the only relevant ISA devices on sparc64 turned out
to be false. While there are sparc64 models where UARTs are the only
devices on the ISA bus there are in fact also low-cost models where all
devices traditionally found on the EBus are hooked up to the ISA bus.
There are also models that use a mix between EBus and ISA devices with
things like an AT keyboard controller and other rather interesting
devices that we might want to support in the futute hook up to the ISA
bus.
In order to not need to add sparc64 specific device_identify methods to
all of the respective ISA drivers and also not add OFW specific code to
the common ISA code make the sparc64 ISA bus code fake up PnP devices so
most ISA drivers probe their devices without further changes.
Unfortunately Sun doesn't adhere to the ISA bindings defined in IEEE
1275-1994 for the properties of most of the ISA devices which would
allow to obtain the vendor and logical IDs from their properties. So we
we just use a simple table which maps the name properties to PnP IDs.
This could be done in a more sophisticated way but I courrently don't
see the need for this. [1]
- Add the children with fully mapped and specified resources (in the OFW
sense) similar to what is done in the EBus code for the IRQ resources
of the children as adjusting the resources and the resource list entries
respectively in isa_alloc_resource() as done perviously causes trouble
with drivers which use rman_get_start(), pass-through or allocate and
release resources multiple times, etc.
Adjusting the resources might be better off in a bus_activate_resource
method but the common ISA code currently doesn't allow for an
isa_activate_resource(). [2]
With this change:
- ppbus(4) and lpt(4) attach and work (modulo ECP mode, which requires
real ISADMA code but it currently only consists of stubs on sparc64).
- atkbdc(4) and atkbdc(4) attach, no further testing done.
- fdc(4) itself attaches but causes a hang while attaching fd0 also
when is DMA disabled, further work in fdc(4) is required here as e.g.
fd0 uses the address of fd1 on sparc64 (not sure if sparc64 supports
more than one floppy drive at all).
All of these drivers previously caused panics in the sparc64 ISA code.
- Minor changes, e.g. use __FBSDID, remove a dupe word in a comment and
declare one global variable which isn't used outside of isa.c static.
o dev/uart/uart_cpu_sparc64.c and modules/uart/Makefile:
- Remove the code for registering the UARTs on the ISA bus from the
sparc64 uart_cpu_identify() again and rely on probing them via PnP.
Original idea by: tmm [1]
No objections by: tmm [1], [2]
current baudrate setting. Use this ioctl() when we don't know the
baudrate of the sysdev (as represented by a 0 value). When the
ioctl() fails, e.g. when the backend hasn't implemented it or the
hardware doesn't provide the means to determine its current baudrate
setting, we invalidate the baudrate setting by setting it to -1.
None of the backends currently implement the new ioctl().
A baudrate we consider insane is silently replaced with 0. When the
baudrate is 0, we will not try to program the hardware. Instead we
leave the communication speed unaltered, maximizing the chance to
have a working console. Obviously this means we allow specifying a
0 baudrate for exactly that purpose.
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
subset ("compatible", "device_type", "model" and "name") of the standard
properties in drivers for devices on Open Firmware supported busses. The
standard properties "reg", "interrupts" und "address" are not covered by
this interface because they are only of interest in the respective bridge
code. There's a remaining standard property "status" which is unclear how
to support properly but which also isn't used in FreeBSD at present.
This ofw_bus kobj-interface allows to replace the various (ebus_get_node(),
ofw_pci_get_node(), etc.) and partially inconsistent (central_get_type()
vs. sbus_get_device_type(), etc.) existing IVAR ones with a common one.
This in turn allows to simplify and remove code-duplication in drivers for
devices that can hang off of more than one OFW supported bus.
- Convert the sparc64 Central, EBus, FHC, PCI and SBus bus drivers and the
drivers for their children to use the ofw_bus kobj-interface. The IVAR-
interfaces of the Central, EBus and FHC are entirely replaced by this. The
PCI bus driver used its own kobj-interface and now also uses the ofw_bus
one. The IVARs special to the SBus, e.g. for retrieving the burst size,
remain.
Beware: this causes an ABI-breakage for modules of drivers which used the
IVAR-interfaces, i.e. esp(4), hme(4), isp(4) and uart(4), which need to be
recompiled.
The style-inconsistencies introduced in some of the bus drivers will be
fixed by tmm@ in a generic clean-up of the respective drivers later (he
requested to add the changes in the "new" style).
- Convert the powerpc MacIO bus driver and the drivers for its children to
use the ofw_bus kobj-interface. This invloves removing the IVARs related
to the "reg" property which were unused and a leftover from the NetBSD
origini of the code. There's no ABI-breakage caused by this because none
of these driver are currently built as modules.
There are other powerpc bus drivers which can be converted to the ofw_bus
kobj-interface, e.g. the PCI bus driver, which should be done together
with converting powerpc to use the OFW PCI code from sparc64.
- Make the SBus and FHC front-end of zs(4) and the sparc64 eeprom(4) take
advantage of the ofw_bus kobj-interface and simplify them a bit.
Reviewed by: grehan, tmm
Approved by: re (scottl)
Discussed with: tmm
Tested with: Sun AX1105, AXe, Ultra 2, Ultra 60; PPC cross-build on i386
with it that need to be understood better before they can be resolved.
This takes time and time is already in short supply.
Reported & tested by: glebius@
future:
rename ttyopen() -> tty_open() and ttyclose() -> tty_close().
We need the ttyopen() and ttyclose() for the new generic cdevsw
functions for tty devices in order to have consistent naming.
o Call kdb_enter() instead of breakpoint().
o Call kdb_alt_break() instead of db_alt_break().
o Make debugging code conditional upon KDB instead of DDB.
does not reliably prevent the triggering of interrupts for all supported
configurations. Thus, the FIFO size probe could cause an interrupt,
which could lead to an interrupt storm in the shared interrupt case.
To prevent this, change ns8250_bus_probe() to use the overflow bit in
the line status register instead of the RX ready bit in the interrupt
identification register to detect whether the FIFO has filled up.
This allows us to clear all bits in the interrupt enable register during
the probe, which should prevent interrupts reliably.
Additionally, the detected FIFO size may be a bit more accurate, because
the overflow bit is only set when the FIFO did actually fill up, while
interrupts would trigger a bit early.
Reviewed and tested on a lot of hardware by: marcel
not as a pending interrupt status, but as a matter of status quo.
Consequently, when there's no data to be transmitted the condition
is not cleared and uart_intr() is stuck in an infinite loop trying
to clear the UART_IPEND_TXIDLE status.
The z8530_bus_ipend() function is changed to return idle only once
after having sent any data.
The root cause for this problem is that we cannot use the interrupt
status bits of the SCC itself. The register that holds the interrupt
status can only be accessed by channel A and holds the status for
both channels. Using the interrupt status register would complicate
the driver because we need to synchronize access to the SCC between
the channels.
Elementary testing: marius
