linux-stable.git/drivers/tty/serial/serial_core.c, branch linux-5.8.y

serial: core: fix console port-lock regression

2020-09-23T11:00:01+00:00

commit e0830dbf71f191851ed3772d2760f007b7c5bc3a upstream.

Fix the port-lock initialisation regression introduced by commit
a3cb39d258ef ("serial: core: Allow detach and attach serial device for
console") by making sure that the lock is again initialised during
console setup.

The console may be registered before the serial controller has been
probed in which case the port lock needs to be initialised during
console setup by a call to uart_set_options(). The console-detach
changes introduced a regression in several drivers by effectively
removing that initialisation by not initialising the lock when the port
is used as a console (which is always the case during console setup).

Add back the early lock initialisation and instead use a new
console-reinit flag to handle the case where a console is being
re-attached through sysfs.

The question whether the console-detach interface should have been added
in the first place is left for another discussion.

Note that the console-enabled check in uart_set_options() is not
redundant because of kgdboc, which can end up reinitialising an already
enabled console (see commit 42b6a1baa3ec ("serial_core: Don't
re-initialize a previously initialized spinlock.")).

Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")
Cc: stable      # 5.7
Signed-off-by: Johan Hovold 
Reviewed-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20200909143101.15389-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman

serial: core: fix port-lock initialisation

2020-09-23T11:00:01+00:00

commit fe88c6489264eaea23570dfdf03e1d3f5f47f423 upstream.

Commit f743061a85f5 ("serial: core: Initialise spin lock before use in
uart_configure_port()") tried to work around a breakage introduced by
commit a3cb39d258ef ("serial: core: Allow detach and attach serial
device for console") by adding a second initialisation of the port lock
when registering the port.

As reported by the build robots [1], this doesn't really solve the
regression introduced by the console-detach changes and also adds a
second redundant initialisation of the lock for normal ports.

Start cleaning up this mess by removing the redundant initialisation and
making sure that the port lock is again initialised once-only for ports
that aren't already in use as a console.

[1] https://lore.kernel.org/r/20200802054852.GR23458@shao2-debian

Fixes: f743061a85f5 ("serial: core: Initialise spin lock before use in uart_configure_port()")
Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")
Cc: stable      # 5.7
Signed-off-by: Johan Hovold 
Reviewed-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20200909143101.15389-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman

serial: core: Initialise spin lock before use in uart_configure_port()

2020-07-10T12:44:46+00:00

The comment near to uart_port_spin_lock_init() says:

  Ensure that the serial console lock is initialised early.
  If this port is a console, then the spinlock is already initialised.

and there is nothing about enabled or disabled consoles. The commit
a3cb39d258ef ("serial: core: Allow detach and attach serial device
for console") made a change, which follows the comment, and also to
prevent reinitialisation of the lock in use, when user detaches and
attaches back the same console device. But this change discovers
another issue, that uart_add_one_port() tries to access a spin lock
that now may be uninitialised. This happens when a driver expects
the serial core to register a console on its behalf. In this case
we must initialise a spin lock before use.

Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")
Reported-by: Marc Zyngier 
Reported-by: Lad Prabhakar 
Reported-by: Guenter Roeck 
Reported-by: Anatoly Pugachev 
Acked-by: Marc Zyngier 
Tested-by: Tony Lindgren 
Cc: Geert Uytterhoeven 
Signed-off-by: Andy Shevchenko 
Tested-by: Lad Prabhakar 
Link: https://lore.kernel.org/r/20200706214903.56148-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: core: fix sysrq overhead regression

2020-06-27T14:16:37+00:00

Commit 8e20fc391711 ("serial_core: Move sysrq functions from header
file") converted the inline sysrq helpers to exported functions which
are now called for every received character, interrupt and break signal
also on systems without CONFIG_MAGIC_SYSRQ_SERIAL instead of being
optimised away by the compiler.

Inlining these helpers again also avoids the function call overhead when
CONFIG_MAGIC_SYSRQ_SERIAL is enabled (e.g. when the port is not used as
a console).

Fixes: 8e20fc391711 ("serial_core: Move sysrq functions from header file")
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Signed-off-by: Johan Hovold 
Cc: stable 
Reviewed-by: Andy Shevchenko 
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>
Link: https://lore.kernel.org/r/20200610152232.16925-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman

Revert "serial: core: Refactor uart_unlock_and_check_sysrq()"

2020-06-27T14:16:37+00:00

This reverts commit da9a5aa3402db0ff3b57216d8dbf2478e1046cae.

In order to ease backporting a fix for a sysrq regression, revert this
rewrite which was since added on top.

The other sysrq helpers now bail out early when sysrq is not enabled;
it's better to keep that pattern here as well.

Note that the __releases() attribute won't be needed after the follow-on
fix either.

Fixes: da9a5aa3402d ("serial: core: Refactor uart_unlock_and_check_sysrq()")
Cc: stable 
Signed-off-by: Johan Hovold 
Reviewed-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20200610152232.16925-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman

tty/serial: fix serial_core.c kernel-doc warnings

2020-06-27T11:56:39+00:00

Fix kernel-doc warnings in serial_core.c:

../drivers/tty/serial/serial_core.c:3300: warning: Function parameter or member 'port' not described in 'uart_get_rs485_mode'
../drivers/tty/serial/serial_core.c:3300: warning: Excess function parameter 'dev' description in 'uart_get_rs485_mode'
../drivers/tty/serial/serial_core.c:3300: warning: Excess function parameter 'rs485conf' description in 'uart_get_rs485_mode'

Fixes: c150c0f362c1 ("serial: Allow uart_get_rs485_mode() to return errno")
Signed-off-by: Randy Dunlap 
Cc: Lukas Wunner 
Cc: Heiko Stuebner 
Cc: Greg Kroah-Hartman 
Cc: linux-serial@vger.kernel.org
Link: https://lore.kernel.org/r/e170db8e-5c8b-27ac-79a4-81b96ac0ca2d@infradead.org
Signed-off-by: Greg Kroah-Hartman

serial: 8250: Support rs485 bus termination GPIO

2020-05-29T10:42:54+00:00

Commit e8759ad17d41 ("serial: uapi: Add support for bus termination")
introduced the ability to enable rs485 bus termination from user space.
So far the feature is only used by a single driver, 8250_exar.c, using a
hardcoded GPIO pin specific to Siemens IOT2040 products.

Provide for a more generic solution by allowing specification of an
rs485 bus termination GPIO pin in the device tree:  Amend the serial
core to retrieve the GPIO from the device tree (or ACPI table) and amend
the default ->rs485_config() callback for 8250 drivers to change the
GPIO on request from user space.

Perhaps 8250_exar.c can be converted to the generic approach in a
follow-up patch.

Signed-off-by: Lukas Wunner 
Reviewed-by: Andy Shevchenko 
Cc: Jan Kiszka 
Link: https://lore.kernel.org/r/94c6c800d1ca9fa04766dd1d43a8272c5ad4bedd.1589811297.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman

serial: Allow uart_get_rs485_mode() to return errno

2020-05-15T12:47:05+00:00

We're about to amend uart_get_rs485_mode() to support a GPIO pin for
rs485 bus termination.  Retrieving the GPIO descriptor may fail, so
allow uart_get_rs485_mode() to return an errno and change all callers
to check for failure.

The GPIO descriptor is going to be stored in struct uart_port.  Pass
that struct to uart_get_rs485_mode() in lieu of a struct device and
struct serial_rs485, both of which are directly accessible from struct
uart_port.

A few drivers call uart_get_rs485_mode() before setting the struct
device pointer in struct uart_port.  Shuffle those calls around where
necessary.

[Heiko Stuebner did the ar933x_uart.c portion, hence his Signed-off-by.]

Signed-off-by: Heiko Stuebner 
Signed-off-by: Lukas Wunner 
Link: https://lore.kernel.org/r/271e814af4b0db3bffbbb74abf2b46b75add4516.1589285873.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman

serial: core: Allow detach and attach serial device for console

2020-03-17T14:57:59+00:00

In the future we would like to disable power management on the serial devices
used as kernel consoles to avoid weird behaviour in some cases. However,
disabling PM may prevent system to go to deep sleep states, which in its turn
leads to the higher power consumption.

Tony Lindgren proposed a work around, i.e. allow user to detach such consoles
to make PM working again. In case user wants to see what's going on, it also
provides a mechanism to attach console back.

Link: https://lists.openwall.net/linux-kernel/2018/09/29/65
Suggested-by: Tony Lindgren 
Signed-off-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20200217114016.49856-3-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: core: Refactor uart_unlock_and_check_sysrq()

2020-03-12T16:16:42+00:00

Refactor uart_unlock_and_check_sysrq() to:

  - explicitly show that we release a port lock which makes
    static analyzers happy:

CHECK   drivers/tty/serial/serial_core.c
.../serial_core.c:3290:17: warning: context imbalance in 'uart_unlock_and_check_sysrq' - unexpected unlock

  - use flags instead of irqflags to avoid confusion with IRQ flags

  - provide one return point

  - be more compact

Signed-off-by: Andy Shevchenko 
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>
Link: https://lore.kernel.org/r/20200310174337.74109-4-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman