kernel/linux.git/drivers/tty/serial/pch_uart.c, branch v6.18.21

pch_uart: Fix dma_sync_sg_for_device() nents value

2025-07-09T11:43:02+00:00

The dma_sync_sg_for_device() functions should be called with the same nents as the dma_map_sg(), not the value the map function returned according to the documentation in Documentation/core-api/dma-api.rst:450: With the sync_sg API, all the parameters must be the same as those passed into the sg mapping API. Fixes: da3564ee027e ("pch_uart: add multi-scatter processing") Cc: stable Signed-off-by: Thomas Fourier Reviewed-by: Andy Shevchenko Link: https://lore.kernel.org/r/20250701113452.18590-2-fourier.thomas@gmail.com Signed-off-by: Greg Kroah-Hartman

serial: pch_uart: Remove legacy PM hook

2025-02-04T13:38:36+00:00

The legacy PM hook was never implemented. If we would like to achieve this, the entire serial subsystem should switch to use runtime PM first. For now, remove unneeded code. Signed-off-by: Andy Shevchenko Link: https://lore.kernel.org/r/20250117141313.592645-1-andriy.shevchenko@linux.intel.com Signed-off-by: Greg Kroah-Hartman

tty: serial: switch from circ_buf to kfifo

2024-04-09T13:28:03+00:00

Switch from struct circ_buf to proper kfifo. kfifo provides much better API, esp. when wrap-around of the buffer needs to be taken into account. Look at pl011_dma_tx_refill() or cpm_uart_tx_pump() changes for example. Kfifo API can also fill in scatter-gather DMA structures, so it easier for that use case too. Look at lpuart_dma_tx() for example. Note that not all drivers can be converted to that (like atmel_serial), they handle DMA specially. Note that usb-serial uses kfifo for TX for ages. omap needed a bit more care as it needs to put a char into FIFO to start the DMA transfer when OMAP_DMA_TX_KICK is set. In that case, we have to do kfifo_dma_out_prepare twice: once to find out the tx_size (to find out if it is worths to do DMA at all -- size >= 4), the second time for the actual transfer. All traces of circ_buf are removed from serial_core.h (and its struct uart_state). Signed-off-by: Jiri Slaby (SUSE) Cc: Al Cooper Cc: Matthias Brugger Cc: AngeloGioacchino Del Regno Cc: Kumaravel Thiagarajan Cc: Tharun Kumar P Cc: Russell King Cc: Vineet Gupta Cc: Richard Genoud Cc: Nicolas Ferre Cc: Alexandre Belloni Cc: Claudiu Beznea Cc: Alexander Shiyan Cc: Baruch Siach Cc: Maciej W. Rozycki Cc: Shawn Guo Cc: Sascha Hauer Cc: Fabio Estevam Cc: Neil Armstrong Cc: Kevin Hilman Cc: Jerome Brunet Cc: Martin Blumenstingl Cc: Taichi Sugaya Cc: Takao Orito Cc: Bjorn Andersson Cc: Konrad Dybcio Cc: Pali Rohár Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Christophe Leroy Cc: Aneesh Kumar K.V Cc: Naveen N. Rao Cc: Manivannan Sadhasivam Cc: Krzysztof Kozlowski Cc: Alim Akhtar Cc: Laxman Dewangan Cc: Thierry Reding Cc: Jonathan Hunter Cc: Orson Zhai Cc: Baolin Wang Cc: Chunyan Zhang Cc: Patrice Chotard Cc: Maxime Coquelin Cc: Alexandre Torgue Cc: David S. Miller Cc: Hammer Hsieh Cc: Peter Korsgaard Cc: Timur Tabi Cc: Michal Simek Cc: Sumit Semwal Cc: Christian König Link: https://lore.kernel.org/r/20240405060826.2521-13-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

serial: pch: Use uart_prepare_sysrq_char().

2024-03-02T21:06:22+00:00

The port lock is a spinlock_t which is becomes a sleeping lock on PREEMPT_RT. The driver splits the locking function into two parts: local_irq_save() and uart_port_lock() and this breaks PREEMPT_RT. Delay handling sysrq until port lock is dropped. Remove the special case in the console write routine an always use the complete locking function. Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20240301215246.891055-19-bigeasy@linutronix.de Signed-off-by: Greg Kroah-Hartman

serial: pch: Remove eg20t_port::lock.

2024-03-02T21:06:22+00:00

The struct eg20t_port has a spinlock_t which is used for locking while access I/O of the device. Then there is the uart_portlock which is sometimes and nests within eg20t_port's lock. The uart_port lock is not used while using the struct in pch_uart_hal_read() which might be okay. Then both locks are used in pch_console_write() which looks odd especially the double try_lock part. All in all it looks like the uart_port's lock could replace eg20t_port's lock and simplify the code. Remove eg20t_port::lock and use uart_port's lock for the lock scope. Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20240301215246.891055-18-bigeasy@linutronix.de Signed-off-by: Greg Kroah-Hartman

serial: pch: Don't initialize uart_port's spin_lock.

2024-03-02T21:06:22+00:00

There is no need to directly initialize the spinlock_t in struct uart_port. The structure is later passed to uart_add_one_port() which initialize the complete struct including the lock member. Remove spin_lock_init() on uart_port's internal lock. Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20240301215246.891055-17-bigeasy@linutronix.de Signed-off-by: Greg Kroah-Hartman

serial: pch: Don't disable interrupts while acquiring lock in ISR.

2024-03-02T21:06:22+00:00

The interrupt service routine is always invoked with disabled interrupts. Remove the _irqsave() from the locking functions in the interrupts service routine/ pch_uart_interrupt(). Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20240301215246.891055-16-bigeasy@linutronix.de Signed-off-by: Greg Kroah-Hartman

serial: pch: Make push_rx() return void.

2024-03-02T21:06:21+00:00

push_rx() returns always 0. Make push_rx() return void. Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20240301215246.891055-15-bigeasy@linutronix.de Signed-off-by: Greg Kroah-Hartman

serial: pch: Invoke handle_rx_to() directly.

2024-03-02T21:06:21+00:00

handle_rx() is only a wrapper around handle_rx_to() without any additional functionality. Invoke handle_rx_to() directly and remove handle_rx(). Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20240301215246.891055-14-bigeasy@linutronix.de Signed-off-by: Greg Kroah-Hartman

serial: pch: Use port lock wrappers

2023-09-18T09:18:13+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/20230914183831.587273-46-john.ogness@linutronix.de Signed-off-by: Greg Kroah-Hartman