linux.git/drivers/tty/serial/serial_core.c, branch v6.6

serial: core: Fix checks for tx runtime PM state

2023-10-07T09:23:47+00:00

Maximilian reported that surface_serial_hub serdev tx does not work during
system suspend. During system suspend, runtime PM gets disabled in
__device_suspend_late(), and tx is unable to wake-up the serial core port
device that we use to check if tx is safe to start. Johan summarized the
regression noting that serdev tx no longer always works as earlier when the
serdev device is runtime PM active.

The serdev device and the serial core controller devices are siblings of
the serial port hardware device. The runtime PM usage count from serdev
device does not propagate to the serial core device siblings, it only
propagates to the parent.

In addition to the tx issue for suspend, testing for the serial core port
device can cause an unnecessary delay in enabling tx while waiting for the
serial core port device to wake-up. The serial core port device wake-up is
only needed to flush pending tx when the serial port hardware device was
in runtime PM suspended state.

To fix the regression, we need to check the runtime PM state of the parent
serial port hardware device for tx instead of the serial core port device.

As the serial port device drivers may or may not implement runtime PM, we
need to also add a check for pm_runtime_enabled().

Reported-by: Maximilian Luz 
Cc: stable 
Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM")
Signed-off-by: Tony Lindgren 
Tested-by: Maximilian Luz 
Reviewed-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20231005075644.25936-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman

serial: Reduce spinlocked portion of uart_rs485_config()

2023-10-03T13:01:18+00:00

Commit 44b27aec9d96 ("serial: core, 8250: set RS485 termination GPIO in
serial core") enabled support for RS485 termination GPIOs behind i2c
expanders by setting the GPIO outside of the critical section protected
by the port spinlock.  Access to the i2c expander may sleep, which
caused a splat with the port spinlock held.

Commit 7c7f9bc986e6 ("serial: Deassert Transmit Enable on probe in
driver-specific way") erroneously regressed that by spinlocking the
GPIO manipulation again.

Fix by moving uart_rs485_config() (the function manipulating the GPIO)
outside of the spinlocked section and acquiring the spinlock inside of
uart_rs485_config() for the invocation of ->rs485_config() only.

This gets us one step closer to pushing the spinlock down into the
->rs485_config() callbacks which actually need it.  (Some callbacks
do not want to be spinlocked because they perform sleepable register
accesses, see e.g. sc16is7xx_config_rs485().)

Stack trace for posterity:

 Voluntary context switch within RCU read-side critical section!
 WARNING: CPU: 0 PID: 56 at kernel/rcu/tree_plugin.h:318 rcu_note_context_switch
 Call trace:
 rcu_note_context_switch
 __schedule
 schedule
 schedule_timeout
 wait_for_completion_timeout
 bcm2835_i2c_xfer
 __i2c_transfer
 i2c_transfer
 i2c_transfer_buffer_flags
 regmap_i2c_write
 _regmap_raw_write_impl
 _regmap_bus_raw_write
 _regmap_write
 _regmap_update_bits
 regmap_update_bits_base
 pca953x_gpio_set_value
 gpiod_set_raw_value_commit
 gpiod_set_value_nocheck
 gpiod_set_value_cansleep
 uart_rs485_config
 uart_add_one_port
 pl011_register_port
 pl011_probe

Fixes: 7c7f9bc986e6 ("serial: Deassert Transmit Enable on probe in driver-specific way")
Suggested-by: Lino Sanfilippo 
Signed-off-by: Lukas Wunner 
Cc: stable@vger.kernel.org # v6.1+
Link: https://lore.kernel.org/r/f3a35967c28b32f3c6432d0aa5936e6a9908282d.1695307688.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman

tty: make tty_operations::write()'s count size_t

2023-08-11T19:12:46+00:00

Unify with the rest of the code. Use size_t for counts and ssize_t for
retval.

Signed-off-by: "Jiri Slaby (SUSE)" 
Link: https://lore.kernel.org/r/20230810091510.13006-30-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

tty: propagate u8 data to tty_operations::put_char()

2023-08-11T19:12:46+00:00

Data are now typed as u8. Propagate this change to
tty_operations::put_char().

Signed-off-by: "Jiri Slaby (SUSE)" 
Cc: Geert Uytterhoeven 
Cc: Heiko Carstens 
Cc: Vasily Gorbik 
Cc: Alexander Gordeev 
Cc: Christian Borntraeger 
Cc: Sven Schnelle 
Cc: Karsten Keil 
Cc: Greg Kroah-Hartman 
Cc: Jiri Slaby 
Cc: Shawn Guo 
Cc: Sascha Hauer 
Cc: Pengutronix Kernel Team 
Cc: Fabio Estevam 
Cc: NXP Linux Team 
Cc: Mathias Nyman 
Link: https://lore.kernel.org/r/20230810091510.13006-29-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

tty: propagate u8 data to tty_operations::write()

2023-08-11T19:12:46+00:00

Data are now typed as u8. Propagate this change to
tty_operations::write().

Signed-off-by: "Jiri Slaby (SUSE)" 
Cc: Richard Henderson 
Cc: Ivan Kokshaysky 
Cc: Matt Turner 
Cc: Geert Uytterhoeven 
Cc: Richard Weinberger 
Cc: Anton Ivanov 
Cc: Johannes Berg 
Cc: Chris Zankel 
Cc: Max Filippov 
Cc: Arnd Bergmann 
Cc: Vaibhav Gupta 
Cc: Jens Taprogge 
Cc: Karsten Keil 
Cc: Scott Branden 
Cc: Ulf Hansson 
Cc: "David S. Miller" 
Cc: Eric Dumazet 
Cc: Jakub Kicinski 
Cc: Paolo Abeni 
Cc: Heiko Carstens 
Cc: Vasily Gorbik 
Cc: Alexander Gordeev 
Cc: Christian Borntraeger 
Cc: Sven Schnelle 
Cc: David Lin 
Cc: Johan Hovold 
Cc: Alex Elder 
Cc: Laurentiu Tudor 
Cc: Jiri Kosina 
Cc: David Sterba 
Cc: Shawn Guo 
Cc: Sascha Hauer 
Cc: Pengutronix Kernel Team 
Cc: Fabio Estevam 
Cc: NXP Linux Team 
Cc: Arnaud Pouliquen 
Cc: Oliver Neukum 
Cc: Mathias Nyman 
Cc: Marcel Holtmann 
Cc: Johan Hedberg 
Cc: Luiz Augusto von Dentz 
Link: https://lore.kernel.org/r/20230810091510.13006-28-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

serial: move WARN_ON() in uart_write() to the condition

2023-07-31T15:16:04+00:00

uart code currently does the following in uart_write() and
uart_flush_buffer():
  if (cond) {
    WARN_ON(1);
    return;
  }

It can be rewritten to more obvious and more readable:
  if (WARN_ON(cond))
    return;

Do so.

Signed-off-by: Jiri Slaby (SUSE) 
Link: https://lore.kernel.org/r/20230731080244.2698-2-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

serial: pass state to __uart_start() directly

2023-07-25T17:21:03+00:00

__uart_start() does not need a tty struct. It works only with
uart_state. So pass the latter directly.

Signed-off-by: Jiri Slaby (SUSE) 
Link: https://lore.kernel.org/r/20230712081811.29004-8-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

serial: make uart_insert_char() accept u8s

2023-07-25T17:21:03+00:00

Both the character and flag are 8-bit values. So switch from unsigned
ints to u8s. The drivers will be cleaned up in the next round.

Signed-off-by: Jiri Slaby (SUSE) 
Link: https://lore.kernel.org/r/20230712081811.29004-7-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

serial: convert uart sysrq handling to u8

2023-07-25T17:21:03+00:00

Propagate u8 from the sysrq code further up to serial's
uart_handle_sysrq_char() and friends.

Signed-off-by: Jiri Slaby (SUSE) 
Link: https://lore.kernel.org/r/20230712081811.29004-6-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

serial: core: Fix error handling for serial_core_ctrl_device_add()

2023-06-02T07:30:55+00:00

Checking for NULL is incorrect as serial_base_ctrl_add() uses ERR_PTR().

Let's also pass any returned error along, there's no reason to translate
all errors to -ENODEV.

Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM")
Signed-off-by: Tony Lindgren 
Reviewed-by: Jiri Slaby 
Link: https://lore.kernel.org/r/20230602070007.59268-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman