linux-stable.git/drivers/tty/serial/serial_core.c, branch linux-3.18.y

serial: fix parisc boot hang

2015-01-27T16:29:39+00:00

commit 68ed7e1c3d236e9e1e60ed6cae22f2c1c4ba2952 upstream.

This is a partial revert of 2f2dafe (serial: serial_core.c: printk
replacement) which gets us booting again.  The real problem seems to be
the _emit path in early boot.  However, until we can root cause it, we
need at least to get boot working.

Fixes: 2f2dafe77df2c78e189a9fa6b1879dffd06ae5a1
Signed-off-by: James Bottomley 
Signed-off-by: Greg Kroah-Hartman

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

2014-11-06T00:14:09+00:00

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 
Cc:  # all
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

Revert "serial/core: Initialize the console pm state"

2014-10-03T04:33:50+00:00

This reverts commit a86713b1536c818972675e6dd8c6e738f0379f1d.

Kevin Hilman writes:

	Multiple boot failures on ARM[1] were bisected down to this
	patch.

	How was this patch tested, and on which platforms?

	Also, the changelog states that this should be done only for
	UART_CAP_SLEEP, but the patch does it for every UART.

	Greg, I suggest this patch be dropped from tty-next until it has
	been better described and tested.

	[1] http://lists.linaro.org/pipermail/kernel-build-reports/2014-October/005550.html

Reported-by: Kevin Hilman 
Cc: Sudhir Sreedharan 
Signed-off-by: Greg Kroah-Hartman

serial/core: Initialize the console pm state

2014-09-29T01:49:48+00:00

For console devices having UART_CAP_SLEEP capability, the uart_pm_state has
to be initialized to UART_PM_STATE_ON. Otherwise the LCR regiser values
are reinitialized when uart_change_pm is called from uart_configure_port.

Signed-off-by: Sudhir Sreedharan 
Signed-off-by: Greg Kroah-Hartman

serial: core: Use spin_lock_irq() in uart_set_termios()

2014-09-24T04:19:35+00:00

uart_set_termios() is called with interrupts enabled; no need to
save and restore the interrupt state when taking the uart port lock.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

serial: core: Privatize tty->hw_stopped

2014-09-24T04:19:35+00:00

tty->hw_stopped is not used by the tty core and is thread-unsafe;
hw_stopped is a member of a bitfield whose fields are updated
non-atomically and no lock is suitable for serializing updates.

Replace serial core usage of tty->hw_stopped with uport->hw_stopped.
Use int storage which works around Alpha EV4/5 non-atomic byte storage,
since uart_port uses different locks to protect certain fields within the
structure.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

serial: core: Privatize modem status enable flags

2014-09-24T04:19:35+00:00

The serial core uses the tty port flags, ASYNC_CTS_FLOW and
ASYNC_CD_CHECK, to track whether CTS and DCD changes should be
ignored or handled. However, the tty port flags are not safe for
atomic bit operations and no lock provides serialized updates.

Introduce the struct uart_port status field to track CTS and DCD
enable states, and serialize access with uart port lock. Substitute
uart_cts_enabled() helper for tty_port_cts_enabled().

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

serial: core: Document and assert lock requirements for irq helpers

2014-09-24T04:19:34+00:00

The serial core provides two helper functions, uart_handle_dcd_change()
and uart_handle_cts_change(), for UART drivers to use at interrupt
time. The serial core expects the UART driver to hold the uart port lock
when calling these helpers to prevent state corruption.

If lockdep enabled, trigger a warning if the uart port lock is not held
when calling these helper functions.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

serial: core: Unwrap tertiary assignment in uart_handle_dcd_change()

2014-09-08T23:23:36+00:00

Prepare for spin lock assertion; move non-trivial assignment into
function body.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

serial: core: Remove unsafe x_char optimization

2014-09-08T23:22:42+00:00

uart_unthrottle() attempts to avoid sending START and the previous
x_char if the previous x_char has not yet been sent. However, this
optimization could leave the sender in a throttled state; for example,
if the sender is throttled and this unthrottle coincides with a manual
tcflow(TCION) from user-space, then neither START would be sent.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman