linux-stable.git/drivers/tty/serial/serial_core.c, branch linux-3.4.y

serial: Fix divide-by-zero fault in uart_get_divisor()

2015-02-02T09:05:15+00:00

commit 547039ec502076e60034eeb79611df3433a99b7d upstream.

uart_get_baud_rate() will return baud == 0 if the max rate is set
to the "magic" 38400 rate and the SPD_* flags are also specified.
On the first iteration, if the current baud rate is higher than the
max, the baud rate is clamped at the max (which in the degenerate
case is 38400). On the second iteration, the now-"magic" 38400 baud
rate selects the possibly higher alternate baud rate indicated by
the SPD_* flag. Since only two loop iterations are performed, the
loop is exited, a kernel WARNING is generated and a baud rate of
0 is returned.

Reproducible with:
 setserial /dev/ttyS0 spd_hi base_baud 38400

Only perform the "magic" 38400 -> SPD_* baud transform on the first
loop iteration, which prevents the degenerate case from recognizing
the clamped baud rate as the "magic" 38400 value.

Reported-by: Robert Święcki 
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Zefan Li

serial_core.c: add put_device() after device_find_child()

2013-05-08T02:51:53+00:00

commit 5a65dcc04cda41f4122aacc37a5a348454645399 upstream.

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: Federico Vaga 
Signed-off-by: Greg Kroah-Hartman

tty: Allow uart_register/unregister/register

2012-06-01T07:18:20+00:00

commit 1e66cded334e6cea596c72f6f650eec351b1e959 upstream.

This is legitimate but because we don't clear the drv->state pointer in the
unregister code causes a bogus BUG().

Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=42880
Signed-off-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

TTY: remove re-assignments to tty_driver members

2012-03-08T19:37:58+00:00

All num, magic and owner are set by alloc_tty_driver. No need to
re-set them on each allocation site.

pti driver sets something different to what it passes to
alloc_tty_driver. It is not a bug, since we don't use the lines
parameter in any way. Anyway this is fixed, and now we do the right
thing.

Signed-off-by: Jiri Slaby 
Acked-by: Tilman Schmidt 
Signed-off-by: Greg Kroah-Hartman

serial: Fix wakeup init logic to speed up startup

2012-01-25T00:29:40+00:00

The synchronize_rcu() call resulting from making every serial driver
wake-up capable (commit b3b708fa) slows boot down on my Tegra2x system
(with CONFIG_PREEMPT disabled).

But this is avoidable since it is the device_set_wakeup_enable() and then
subsequence disable which causes the delay. We might as well just make
the device wakeup capable but not actually enable it for wakeup until
needed.

Effectively the current code does this:

	device_set_wakeup_capable(dev, 1);
	device_set_wakeup_enable(dev, 1);
	device_set_wakeup_enable(dev, 0);

We can just drop the last two lines.

Before this change my boot log says:
[    0.227062] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
[    0.702928] serial8250.0: ttyS0 at MMIO 0x70006040 (irq = 69) is a Tegra

after:
[    0.227264] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
[    0.227983] serial8250.0: ttyS0 at MMIO 0x70006040 (irq = 69) is a Tegra

for saving of 450ms.

Suggested-by: Rafael J. Wysocki 
Acked-by: Rafael J. Wysocki 
Signed-off-by: Simon Glass 
Signed-off-by: Greg Kroah-Hartman

serial: use DIV_ROUND_CLOSEST instead of open coding it

2012-01-05T00:18:54+00:00

Signed-off-by: Uwe Kleine-König 
Signed-off-by: Greg Kroah-Hartman

TTY: serial, extract uart_port_startup

2011-11-15T23:59:04+00:00

Extract ASYNC_INITIALIZED/TTY_IO_ERROR handling from uart_startup.
This will be useful for tty port helpers. These flags are handled
by the helpers instead.

So we create a new function uart_port_startup without touching these
flags there. And we keep uart_startup with the exact behavior as
before. We need that one because we start/stop the device from other
paths than open/close/hangup.

Signed-off-by: Jiri Slaby 
Cc: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

TTY: serial, fill uart_port_shutdown

2011-11-15T23:59:03+00:00

Let's fill the port_ops->shutdown. We will need this for hangup and
close port helpers.

We don't need to touch DTR/RTS registers in uart_port_shutdown. They
are set to off from port_close_start properly already.

Also we don't need to pin the TTY_IO_ERROR bit. This will be done in
close/hangup paths.

We leave uart_shutdown as is, because it is used (and will be) from
several paths now. Like from suspend.

The point is to not touch ASYNC_INITIALIZED bit. It will be set (and
checked) properly by the tty port helpers.

Signed-off-by: Jiri Slaby 
Cc: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

TTY: serial, define uart_port_activate/shutdown

2011-11-15T23:59:02+00:00

This is a preparation for the next patches which will move the stuff
from uart_open and uart_close/hangup here. Then we will use
tty_port_* helpers.

Signed-off-by: Jiri Slaby 
Cc: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

TTY: serial, inline uart_get

2011-11-15T23:59:01+00:00

We need to expand uart_get into uart_open. We need it to move on with
conversion to use tty_port_open helper. After we do this, the code
will be much more similar to what tty_port_open does.

Signed-off-by: Jiri Slaby 
Cc: Alan Cox 
Signed-off-by: Greg Kroah-Hartman