When a serial port is closed, uart_close() takes care of shutting down the
hardware, and powering it down.

When a serial port is unbound while in use, uart_close() bypasses all of
this, as this is supposed to be done through uart_hangup() (invoked via
tty_vhangup() in uart_remove_one_port()).

However, uart_hangup() does not set the hardware's power state, leaving it
powered up.  This may also lead to unbounded nesting counts in clock and
power management, depending on their internal implementation.

Make sure to power down the port in uart_hangup(), except when the port is
used as a serial console.

For serial consoles, this operation must be postponed until after the port
becomes completely unused. This case is not fixed yet, as it depends on a
(future) fix for the tty->count vs. port->count imbalance on failed
uart_open().

After this, the module clock used by the sh-sci driver is disabled on
unbind while the serial port is in use.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

If the serial_core ring buffer empties just as the tty layer receives
an XOFF, then start_tx will never be called when the tty layer
receives an XON as the serial_core ring buffer is empty.  This will
possibly leave a few bytes trapped in the fifo for drivers that
disable the transmitter when flow controlled.
Signed-off-by: NSeth Bollinger <sethb@digi.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

When unbinding a serial driver that's being used as a serial console,
the kernel may crash with a NULL pointer dereference in a uart_*() function
called from uart_close () (e.g. uart_flush_buffer() or
uart_chars_in_buffer()).

To fix this, let uart_close() check for port->count == 0. If this is the
case, bail out early. Else tty_port_close_start() will make the port
counts inconsistent, printing out warnings like

    tty_port_close_start: tty->count = 1 port count = 0.

and

    tty_port_close_start: count = -1

and once uport == NULL, it will also crash.

Also fix the related crash in pr_debug() by checking for a non-NULL uport
first.

Detailed description:

On driver unbind, uart_remove_one_port() is called. Basically it;
  - marks the port dead,
  - calls tty_vhangup(),
  - sets state->uart_port = NULL.

What will happen depends on whether the port is just in use by e.g. getty,
or was also opened as a console.

A. If the tty was not opened as a console:

  - tty_vhangup() will (in __tty_hangup()):
      - mark all file descriptors for this tty hung up by pointing them to
	hung_up_tty_fops,
      - call uart_hangup(), which sets port->count to 0.

  - A subsequent uart_open() (this may be through /dev/ttyS*, or through
    /dev/console if this is a serial console) will fail with -ENXIO as the
    port was marked dead,
  - uart_close() after the failed uart_open() will return early, as
    tty_hung_up_p() (called from tty_port_close_start()) will notice it was
    hung up.

B. If the tty was also opened as a console:

  - tty_vhangup() will (in __tty_hangup()):
      - mark non-console file descriptors for this tty hung up by pointing
	them to hung_up_tty_fops,
      - NOT call uart_hangup(), but instead call uart_close() for every
        non-console file descriptor, so port->count will still have a
	non-zero value afterwards.

  - A subsequent uart_open() will fail with -ENXIO as the port was
    marked dead,
  - uart_close() after the failed uart_open() starts to misbehave:
      - tty_hung_up_p() will not notice it was hung up,
      - As port->count is non-zero, tty_port_close_start() will decrease
        port->count, making the tty and port counts inconsistent. Later,
	warnings like these will be printed:

	    tty_port_close_start: tty->count = 1 port count = 0.

	and
	    tty_port_close_start: count = -1

      - If all of this happens after state->uart_port was set to zero, a
        NULL pointer dereference will happen.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@linux-m68k.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Suggested-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGeert Uytterhoeven <geert+renesas@linux-m68k.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: NGeert Uytterhoeven <geert+renesas@linux-m68k.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-serial@vger.kernel.org
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: NGeert Uytterhoeven <geert+renesas@linux-m68k.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-serial@vger.kernel.org
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

If the serial port being removed is used as a console, it must also be
unregistered from the console subsystem using unregister_console().

uart_ops.release_port() will release resources (e.g. iounmap() the serial
port registers), causing a crash on subsequent kernel output if the console
is still registered.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@linux-m68k.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The uart_set_options() code unconditionally initalizes the spinlock
on the port. This can cause a deadlock in some situations.

One instance that exposed the problem, was when writing to
/sys/module/kgdboc/parameters/kgdboc to use ttyS0 when the console
is already running on ttyS0. If the spinlock is re-initialized
while the lock is held due to output to the console, there
is a deadlock.

Assume the spinlock is initialized if the port is a console.
Signed-off-by: NRandy Witt <rewitt@declaratino.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Some serial ports will not use the standard base baud rate. Report
this after initialization so it might be discovered and used for early
console configuration.
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Move "uart_console" definition to serial core header file, so that it can be
used by serial drivers.
Get rid of the uart_console defintion from mpc52xx_uart driver.

Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Rajendra nayak <rnayak@ti.com>
Reviewed-by: NFelipe Balbi <balbi@ti.com>
Reviewed-by: NKevin Hilman <khilman@linaro.org>
Tested-by: NKevin Hilman <khilman@linaro.org>
Signed-off-by: NSourav Poddar <sourav.poddar@ti.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The serial core uses device_find_child() but does not drop the reference to
the retrieved child after using it. This patch add the missing put_device().

What I have done to test this issue.

I used a machine with an AMBA PL011 serial driver. I tested the patch on
next-20120408 because the last branch [next-20120415] does not boot on this
board.

For test purpose, I added some pr_info() messages to print the refcount
after device_find_child() (lines: 1937,2009), and after put_device()
(lines: 1947, 2021).

Boot the machine *without* put_device(). Then:

echo reboot > /sys/power/disk
echo disk > /sys/power/state
[   87.058575] uart_suspend_port:1937 refcount 4
[   87.058582] uart_suspend_port:1947 refcount 4
[   87.098083] uart_resume_port:2009refcount 5
[   87.098088] uart_resume_port:2021 refcount 5

echo disk > /sys/power/state
[  103.055574] uart_suspend_port:1937 refcount 6
[  103.055580] uart_suspend_port:1947 refcount 6
[  103.095322] uart_resume_port:2009 refcount 7
[  103.095327] uart_resume_port:2021 refcount 7

echo disk > /sys/power/state
[  252.459580] uart_suspend_port:1937 refcount 8
[  252.459586] uart_suspend_port:1947 refcount 8
[  252.499611] uart_resume_port:2009 refcount 9
[  252.499616] uart_resume_port:2021 refcount 9

The refcount continuously increased.

Boot the machine *with* this patch. Then:

echo reboot > /sys/power/disk
echo disk > /sys/power/state
[  159.333559] uart_suspend_port:1937 refcount 4
[  159.333566] uart_suspend_port:1947 refcount 3
[  159.372751] uart_resume_port:2009 refcount 4
[  159.372755] uart_resume_port:2021 refcount 3

echo disk > /sys/power/state
[  185.713614] uart_suspend_port:1937 refcount 4
[  185.713621] uart_suspend_port:1947 refcount 3
[  185.752935] uart_resume_port:2009 refcount 4
[  185.752940] uart_resume_port:2021 refcount 3

echo disk > /sys/power/state
[  207.458584] uart_suspend_port:1937 refcount 4
[  207.458591] uart_suspend_port:1947 refcount 3
[  207.498598] uart_resume_port:2009 refcount 4
[  207.498605] uart_resume_port:2021 refcount 3

The refcount correctly handled.
Signed-off-by: NFederico Vaga <federico.vaga@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The only part of proc_dir_entry the code outside of fs/proc
really cares about is PDE(inode)->data.  Provide a helper
for that; static inline for now, eventually will be moved
to fs/proc, along with the knowledge of struct proc_dir_entry
layout.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

hardpps() functionality is provided through the N_PPS line
discipline now. The new function signature was added in commit
025b40ab (2011-01-12). There was no previous macro or
function hardpps(), at least since before the initial commit of
v2.6.12 in 2005. It's unlikely this code has been compiled since.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGeorge Spelvin <linux@horizon.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

An extension of the previous commit, there is no semantic change
here, just fewer lines of source code.
Signed-off-by: NGeorge Spelvin <linux@horizon.com>
Acked-by: NRodolfo Giometti <giometti@enneenne.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The PPS (Pulse-Per-Second) line discipline has developed a number of
unhealthy attachments to core tty data and functions, ultimately leading
to its breakage.

The previous patches fixed the crashing.  This one reduces coupling further
by eliminating the timestamp parameter from the dcd_change ldisc method.
This reduces header file linkage and makes the extension more generic,
and the timestamp read is delayed only slightly, from just before the
ldisc->ops->dcd_change method call to just after.

Fix attendant build breakage in
    drivers/tty/n_tty.c
    drivers/tty/tty_buffer.c
    drivers/staging/speakup/selection.c
    drivers/staging/dgrp/dgrp_*.c

Cc: William Hubbs <w.d.hubbs@gmail.com>
Cc: Chris Brannon <chris@the-brannons.com>
Cc: Kirk Reiser <kirk@braille.uwo.ca>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGeorge Spelvin <linux@horizon.com>
Acked-by: NRodolfo Giometti <giometti@enneenne.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

  for extern function uart_remove_one_port:
    need check pointer whether be NULL, before the main work.
    just like what the other extern function uart_add_one_port has done.
    uart_add_one_port and uart_remove_one_port are pair

  information:
    for the callers (such as drivers/tty/serial/jsm: jsm_tty.c, jsm_driver.c)
    they realy assume that:
      they still can call uart_remove_one_port, after uart_add_one_port failed
    we (as an extern function), have to understand it (just like kfree).
Signed-off-by: NChen Gang <gang.chen@asianux.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

One point is to have less places where we actually need tty pointer.
The other is that low_latency is bound to buffer processing and
buffers are now in tty_port. So it makes sense to move low_latency to
tty_port too.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.

tty_insert_flip_char is the next one to proceed. This one is used all
over the code, so the patch is huge.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: NKevin Cernekee <cernekee@gmail.com>
Acked-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The serial core is using power states lifted from ACPI for no
good reason. Remove this reference from the documentation and
alter all users to use an enum specific to the serial core
instead, and define it in <linux/serial_core.h>.
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
Acked-by: NAlan Cox <alan@linux.intel.com>
Reviewed-by: NDaniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

serial_core.c usually does

	if (HIGH_BITS_OFFSET)
		expr-involving-HIGH_BITS_OFFSET()

at least to avoid generating useless code on 32-bit machines, where
HIGH_BITS_OFFSET is zero.  Do that in uart_get_attr_port().

Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

After commit "TTY: move tty buffers to tty_port", the tty buffers are
not freed in some drivers. This is because tty_port_destructor is not
called whenever a tty_port is freed. This was an assumption I counted
with but was unfortunately untrue. So fix the drivers to fulfil this
assumption.

To be sure, the TTY buffers (and later some stuff) are gone along with
the tty_port, we have to call tty_port_destroy at tear-down places.
This is mostly where the structure containing a tty_port is freed.
This patch does exactly that -- put tty_port_destroy at those places.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Without this we will shift data into oblivion and give wrong results on
some configurations
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add two callbacks for hardware assisted flow control; we need to know
when the tty layers want us to stop and restart due to their buffer
levels.

Call a driver specific throttle/unthrottle function if and only if the
driver indicates that it is using an enabled hardware assisted flow
control method, otherwise fall back to the non-hardware assisted
methods.
Acked-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Ports which are handling h/w flow control in hardware must not have
their RTS state altered depending on the tty's hardware-stopped state.
Avoid this additional logic when setting the termios state.
Acked-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Ports which are capable of handling s/w flow control in hardware to
know when the s/w flow control termios settings are changed.  Add a
flag to allow the low level serial drivers to indicate that they
support this, and these changes should be propagated to them.
Acked-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

This is to make the following change more clear.
Acked-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

We pass both port and state because the original caller had both to hand.
With all the attribute callers this won't be true so do the conversion in
the function itself.

The current callers all do lock/query/unlock. This won't be true for future
set based cases but there are plenty of get ones that will exist so split
the code with a helper for the future cases.
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The two patches needed are now in the tree. The first added the sysfs
interface and directly accesses the uartclk. The second provides a
proper interface for getting the values.

Wire them together.

This formes a basis for both get and set methods for any of the other uart
properties and we can now fill them out further.
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

It was noticed that polling drivers (like KGDB) are not able to use
serial ports if the ports were not previously initialized via console.
I.e.  when booting with console=ttyAMA0 kgdboc=ttyAMA0, everything works
fine, but with console=ttyFOO kgdboc=ttyAMA0, the kgdboc doesn't work.

This is because we don't initialize the hardware. Calling ->startup() is
not an option, because drivers request interrupts there, and drivers
fail to handle situations when tty isn't opened with interrupts enabled.

So, we have to implement a new callback (actually, tty_ops already have
a similar callback), which does everything needed to initialize just the
hardware.
Signed-off-by: NAnton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

If a serial driver is called post hangup with a second DCD event then we
will attempt to get the ldisc of NULL. Check we have a tty before trying to
do anything with it.

This is still only safe within the uart layer if the caller holds the
relevant uart locks. We could do with a version where the tty is passed for
more general use.
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Added tty_device_create_release() and bound to dev->release in
tty_register_device_attr().
Added tty_port_register_device_attr() and used in uart_add_one_port()
instead of tty_register_device_attr().
Signed-off-by: NTomas Hlavacek <tmshlvck@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Added file /sys/devices/.../tty/ttySX/uartclk to allow reading
uartclk value in struct uart_port in serial_core via sysfs.

tty_register_device() has been generalized and refactored in order
to add support for setting drvdata and attribute_group to the device.
Signed-off-by: NTomas Hlavacek <tmshlvck@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

sizeof when applied to a pointer typed expression gives the
size of the pointer.

Generated by: scripts/coccinelle/misc/noderef.cocci
Signed-off-by: NFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

In most of the time, the driver needs to check if the cts flow control
is enabled. But now, the driver checks the ASYNC_CTS_FLOW flag manually,
which is not a grace way. So add a new wraper function to make the code
tidy and clean.
Signed-off-by: NHuang Shijie <shijie8@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

We want them split so that we can call them from setserial functionality
where we copy to/from user space and do the locking, but also from sysfs
where in future we'll want to came them within a sysfs context.
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently we have no way to assign tty->port while performing tty
installation. There are two ways to provide the link tty_struct =>
tty_port. Either by calling tty_port_install from tty->ops->install or
tty_port_register_device called instead of tty_register_device when
the device is being set up after connected.

In this patch we modify most of the drivers to do the latter. When the
drivers use tty_register_device and we have tty_port already, we
switch to tty_port_register_device. So we have the tty_struct =>
tty_port link for free for those.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Acked-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently, serial drivers don't report buffer overruns. When a buffer overrun
occurs, tty_insert_flip_char returns 0, and no attempt is made to insert that
same character again (i.e. it is lost). This patch reports buffer overruns via
the buf_overrun field in the port's icount structure.
Signed-off-by: NCorbin Atkinson <corbin.atkinson@xxxxxx>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This will let us sort out a whole pile of tty related races. The
alternative would be to keep points and refcount the termios objects.
However
1. They are tiny anyway
2. Many devices don't use the stored copies
3. We can remove a pty special case
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>