kernel/linux.git/drivers/tty/serial/serial_core.c, branch v6.7

serial: core: Fix runtime PM handling for pending tx

2023-10-24T09:35:29+00:00

Richard reported that a serial port may end up sometimes with tx data pending in the buffer for long periods of time. Turns out we bail out early on any errors from pm_runtime_get(), including -EINPROGRESS. To fix the issue, we need to ignore -EINPROGRESS as we only care about the runtime PM usage count at this point. We check for an active runtime PM state later on for tx. Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM") Cc: stable Reported-by: Richard Purdie Cc: Bruce Ashfield Cc: Mikko Rapeli Cc: Paul Gortmaker Cc: Randy MacLeod Signed-off-by: Tony Lindgren Tested-by: Richard Purdie Link: https://lore.kernel.org/r/20231023074856.61896-1-tony@atomide.com Signed-off-by: Greg Kroah-Hartman

serial: core: tidy invalid baudrate handling in uart_get_baud_rate

2023-10-16T18:15:41+00:00

uart_get_baud_rate has input parameters 'min' and 'max' limiting the range of acceptable baud rates from the caller's perspective. If neither current or old termios structures have acceptable baud rate setting and 9600 is not in the min/max range either the function returns 0 and issues a warning. However for a UART that does not support speed of 9600 baud this is expected behavior. Clarify that 0 can be (and always could be) returned from the uart_get_baud_rate. Don't issue a warning in that case. Signed-off-by: Max Filippov Link: https://lore.kernel.org/r/20231010085926.1021667-2-jcmvbkbc@gmail.com Signed-off-by: Greg Kroah-Hartman

Merge 6.6-rc6 into tty-next

2023-10-16T08:18:49+00:00

We need the tty/serial fixes in here as well for testing, and this resolves merge conflicts in: drivers/tty/serial/serial_core.c as reported in linux-next Reported-by: Stephen Rothwell Signed-off-by: Greg Kroah-Hartman

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: initialize retinfo in uart_get_info()

2023-10-07T09:21:42+00:00

If this check ever triggers static int uart_get_info(struct tty_port *port, struct serial_struct *retinfo) { uport = uart_port_check(state); if (!uport) goto out; then all those sysfs users will print stack contents to userspace. Signed-off-by: Alexey Dobriyan Link: https://lore.kernel.org/r/967b9ef1-fb36-48bf-9e6a-1b99af24c052@p183 Signed-off-by: Greg Kroah-Hartman

serial: core: Simplify uart_get_rs485_mode()

2023-10-05T07:41:26+00:00

Simplify uart_get_rs485_mode() by using temporary variable for the GPIO descriptor. With that, use proper type for the flags of the GPIO descriptor. Signed-off-by: Andy Shevchenko Link: https://lore.kernel.org/r/20231003142346.3072929-1-andriy.shevchenko@linux.intel.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

serial: core: Use port lock wrappers

2023-09-18T09:18:14+00:00

When a serial port is used for kernel console output, then all modifications to the UART registers which are done from other contexts, e.g. getty, termios, are interference points for the kernel console. So far this has been ignored and the printk output is based on the principle of hope. The rework of the console infrastructure which aims to support threaded and atomic consoles, requires to mark sections which modify the UART registers as unsafe. This allows the atomic write function to make informed decisions and eventually to restore operational state. It also allows to prevent the regular UART code from modifying UART registers while printk output is in progress. All modifications of UART registers are guarded by the UART port lock, which provides an obvious synchronization point with the console infrastructure. To avoid adding this functionality to all UART drivers, wrap the spin_[un]lock*() invocations for uart_port::lock into helper functions which just contain the spin_[un]lock*() invocations for now. In a subsequent step these helpers will gain the console synchronization mechanisms. Converted with coccinelle. No functional change. Signed-off-by: Thomas Gleixner Signed-off-by: John Ogness Link: https://lore.kernel.org/r/20230914183831.587273-58-john.ogness@linutronix.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