The patch below fixes serial console hangs as seen on IP22
machines. Typically, while booting, the machine hangs for ~1 minute
displaying "INIT: ", then the same thing happens again when init
enters in the designated runlevel and finally the getty process on
ttyS0 hangs indefinitely (though strace'ing it helps).
strace (-e raw=ioctl, otherwise the ioctl() translation is utterly
bogus) reveals that getty hangs on ioctl() 0x540f which happens to be
TCSETSW (I saw it hang on another console ioctl() but couldn't
reproduce that one).
A diff between ip22zilog and sunzilog revealed the following
differences:
1. the channel A flag being set on up.port.flags instead of up.flags
2. the channel A flag being set on what is marked as being channel B
3. sunzilog has a call to uart_update_timeout(port, termios->c_cflag, baud);
at the end of sunzilog_set_termios(), which ip22zilog lacks (on
purpose ?)
The patch below addresses point 1 and fixes the serial console hangs
just fine. However point 2 should be investigated by someone familiar
with the IP22 Zilog; it's probably OK as is but even if it is, a
comment in ip22zilog.c is badly needed.
Point 3 is left as an exercise for whoever feels like digging into
ip22zilog :)
These are the main obvious differences between ip22zilog and
sunzilog. Newer versions of sunzilog (Linus's git tree as of today)
are more close to ip22zilog as the sbus_{write,read}b have been
changed into simple {write,read}b, which shrinks the diff by a fair
amount. Resyncing both drivers should be doable in a few hours time
now for someone familiar with the IP22 Zilog hardware.
Signed-off-by: Julien BLACHE <jb@jblache.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Glen Turner reported that writing LFCR rather than the more
traditional CRLF causes issues with some terminals.
Since this aflicts many serial drivers, extract the common code
to a library function (uart_console_write) and arrange for each
driver to supply a "putchar" function.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Incorrect uart_write_wakeup() calls cause reference to a NULL tty
pointer. This has been fixed in the sunsab and sunzilog serial drivers
in October 2005. Update the ip22zilog, which is based on sunzilog,
accordingly.
Signed-off-by: Martin Michlmayr <tbm@cyrius.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk
The API and code have been through various bits of initial review by
serial driver people but they definitely need to live somewhere for a
while so the unconverted drivers can get knocked into shape, existing
drivers that have been updated can be better tuned and bugs whacked out.
This replaces the tty flip buffers with kmalloc objects in rings. In the
normal situation for an IRQ driven serial port at typical speeds the
behaviour is pretty much the same, two buffers end up allocated and the
kernel cycles between them as before.
When there are delays or at high speed we now behave far better as the
buffer pool can grow a bit rather than lose characters. This also means
that we can operate at higher speeds reliably.
For drivers that receive characters in blocks (DMA based, USB and
especially virtualisation) the layer allows a lot of driver specific
code that works around the tty layer with private secondary queues to be
removed. The IBM folks need this sort of layer, the smart serial port
people do, the virtualisers do (because a virtualised tty typically
operates at infinite speed rather than emulating 9600 baud).
Finally many drivers had invalid and unsafe attempts to avoid buffer
overflows by directly invoking tty methods extracted out of the innards
of work queue structs. These are no longer needed and all go away. That
fixes various random hangs with serial ports on overflow.
The other change in here is to optimise the receive_room path that is
used by some callers. It turns out that only one ldisc uses receive room
except asa constant and it updates it far far less than the value is
read. We thus make it a variable not a function call.
I expect the code to contain bugs due to the size alone but I'll be
watching and squashing them and feeding out new patches as it goes.
Because the buffers now dynamically expand you should only run out of
buffering when the kernel runs out of memory for real. That means a lot of
the horrible hacks high performance drivers used to do just aren't needed any
more.
Description:
tty_insert_flip_char is an old API and continues to work as before, as does
tty_flip_buffer_push() [this is why many drivers dont need modification]. It
does now also return the number of chars inserted
There are also
tty_buffer_request_room(tty, len)
which asks for a buffer block of the length requested and returns the space
found. This improves efficiency with hardware that knows how much to
transfer.
and tty_insert_flip_string_flags(tty, str, flags, len)
to insert a string of characters and flags
For a smart interface the usual code is
len = tty_request_buffer_room(tty, amount_hardware_says);
tty_insert_flip_string(tty, buffer_from_card, len);
More description!
At the moment tty buffers are attached directly to the tty. This is causing a
lot of the problems related to tty layer locking, also problems at high speed
and also with bursty data (such as occurs in virtualised environments)
I'm working on ripping out the flip buffers and replacing them with a pool of
dynamically allocated buffers. This allows both for old style "byte I/O"
devices and also helps virtualisation and smart devices where large blocks of
data suddenely materialise and need storing.
So far so good. Lots of drivers reference tty->flip.*. Several of them also
call directly and unsafely into function pointers it provides. This will all
break. Most drivers can use tty_insert_flip_char which can be kept as an API
but others need more.
At the moment I've added the following interfaces, if people think more will
be needed now is a good time to say
int tty_buffer_request_room(tty, size)
Try and ensure at least size bytes are available, returns actual room (may be
zero). At the moment it just uses the flipbuf space but that will change.
Repeated calls without characters being added are not cumulative. (ie if you
call it with 1, 1, 1, and then 4 you'll have four characters of space. The
other functions will also try and grow buffers in future but this will be a
more efficient way when you know block sizes.
int tty_insert_flip_char(tty, ch, flag)
As before insert a character if there is room. Now returns 1 for success, 0
for failure.
int tty_insert_flip_string(tty, str, len)
Insert a block of non error characters. Returns the number inserted.
int tty_prepare_flip_string(tty, strptr, len)
Adjust the buffer to allow len characters to be added. Returns a buffer
pointer in strptr and the length available. This allows for hardware that
needs to use functions like insl or mencpy_fromio.
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch changes the way serial ports are locked when getting modem
status. This change is necessary because we will need to atomically
read the modem status and take action depending on the CTS status.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Julien BLACHE