kernel/linux.git/include/linux/serial_8250.h, branch v7.3-rc1

serial: 8250: allow low-level drivers to override break control

2026-08-03T14:51:57+00:00

Some UARTs require driver-specific handling for break signaling, which cannot be expressed by the generic 8250 break implementation alone. Add an optional uart_port break_ctl callback and route serial8250_break_ctl() through it when provided. Rename the existing 8250 implementation to serial8250_do_break_ctl() and export it so low-level drivers can reuse the default 8250 behavior when appropriate. Signed-off-by: Crescent Hsieh Link: https://patch.msgid.link/20260731074820.735619-11-crescentcy.hsieh@moxa.com Signed-off-by: Greg Kroah-Hartman

serial: 8250: Switch to nbcon console, take 2

2026-07-30T14:48:22+00:00

Implement the necessary callbacks to switch the 8250 console driver to perform as an nbcon console. Add implementations for the nbcon console callbacks: ->write_atomic() ->write_thread() ->device_lock() ->device_unlock() and add CON_NBCON to the initial @flags. All hardware access in the callbacks is within unsafe sections. The ->write_atomic() and ->write_thread() callbacks allow safe handover/takeover per byte and add a preceding newline if they take over from another context mid-line. For the ->write_atomic() callback, a new irq_work is used to defer modem control since it may be called from a context that does not allow waking up tasks. During suspend/resume the irq_work is not used as this has been shown to cause suspend problems for some hardware. Upon resume, any pending modem control is performed. Note: A new __serial8250_clear_IER() is introduced for direct clearing of UART_IER during console writing (which will not be holding the port lock for atomic printing or KDB/KGDB). This allows restoring a lockdep check to serial8250_clear_IER() in a follow-up commit. Signed-off-by: John Ogness Link: https://patch.msgid.link/20260729120439.281252-2-john.ogness@linutronix.de Signed-off-by: Greg Kroah-Hartman

serial: 8250: Add serial8250_handle_irq_locked()

2026-03-12T14:34:15+00:00

8250_port exports serial8250_handle_irq() to HW specific 8250 drivers. It takes port's lock within but a HW specific 8250 driver may want to take port's lock itself, do something, and then call the generic handler in 8250_port but to do that, the caller has to release port's lock for no good reason. Introduce serial8250_handle_irq_locked() which a HW specific driver can call while already holding port's lock. As this is new export, put it straight into a namespace (where all 8250 exports should eventually be moved). Tested-by: Bandal, Shankar Tested-by: Murthy, Shanth Cc: stable Reviewed-by: Andy Shevchenko Signed-off-by: Ilpo Järvinen Link: https://patch.msgid.link/20260203171049.4353-4-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman

serial: 8250: sanitize uart_port::serial_{in,out}() types

2025-06-17T11:42:34+00:00

uart_port::{serial_in,serial_out} (and plat_serial8250_port::* likewise) historically use: * 'unsigned int' for 32-bit register values in reads and writes, and * 'int' for offsets. Make them sane such that: * 'u32' is used for register values, and * 'unsigned int' is used for offsets. While at it, name hooks' parameters, so it is clear what is what. Signed-off-by: "Jiri Slaby (SUSE)" Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Christophe Leroy Cc: Ilpo Järvinen Cc: Andy Shevchenko Cc: Paul Cercueil Cc: Vladimir Zapolskiy Cc: Kunihiko Hayashi Cc: Masami Hiramatsu Reviewed-by: Andy Shevchenko Link: https://lore.kernel.org/r/20250611100319.186924-9-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

Revert "serial: 8250: Switch to nbcon console"

2025-01-22T09:35:56+00:00

This reverts commit b63e6f60eab45b16a1bf734fef9035a4c4187cd5. kernel test robot has found problems with this commit so revert it for now. Link: https://lore.kernel.org/r/202501221029.fb0d574d-lkp@intel.com Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202501221029.fb0d574d-lkp@intel.com Cc: John Ogness Cc: Petr Mladek Signed-off-by: Greg Kroah-Hartman

serial: 8250: Switch to nbcon console

2025-01-10T15:08:25+00:00

Implement the necessary callbacks to switch the 8250 console driver to perform as an nbcon console. Add implementations for the nbcon console callbacks: ->write_atomic() ->write_thread() ->device_lock() ->device_unlock() and add CON_NBCON to the initial @flags. All register access in the callbacks are within unsafe sections. The ->write_atomic() and ->write_thread() callbacks allow safe handover/takeover per byte and add a preceding newline if they take over from another context mid-line. For the ->write_atomic() callback, a new irq_work is used to defer modem control since it may be called from a context that does not allow waking up tasks. Note: A new __serial8250_clear_IER() is introduced for direct clearing of UART_IER. This will allow to restore the lockdep check to serial8250_clear_IER() in a follow-up commit. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Tested-by: Petr Mladek Link: https://lore.kernel.org/r/20250107212702.169493-6-john.ogness@linutronix.de Signed-off-by: Greg Kroah-Hartman

serial: 8250: Provide flag for IER toggling for RS485

2025-01-10T15:08:25+00:00

For RS485 mode, if SER_RS485_RX_DURING_TX is not available, the console ->write() callback needs to enable/disable Tx. It does this by calling the ->rs485_start_tx() and ->rs485_stop_tx() callbacks. However, some of these callbacks also disable/enable interrupts and makes power management calls. This causes 2 problems for console writing: 1. A console write can occur in contexts that are illegal for pm_runtime_*(). It is not even necessary for console writing to use pm_runtime_*() because a console already does this in serial8250_console_setup() and serial8250_console_exit(). 2. The console ->write() callback already handles disabling/enabling the interrupts by properly restoring the previous IER value. Add an argument @toggle_ier to the ->rs485_start_tx() and ->rs485_stop_tx() callbacks to specify if they may disable/enable receive interrupts while using pm_runtime_*(). Console writing will not allow the toggling. For all call sites other than console writing there is no functional change. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20250107212702.169493-5-john.ogness@linutronix.de Signed-off-by: Greg Kroah-Hartman

serial: remove quot_frac from serial8250_do_set_divisor()

2024-08-07T11:13:35+00:00

quot_frac is unused in serial8250_do_set_divisor() since commit b2b4b8ed3c06 (serial: 8250_exar: Move custom divisor support out from 8250_port). So no point to pass it. Signed-off-by: Jiri Slaby (SUSE) Cc: Ilpo Järvinen Cc: Andy Shevchenko Cc: Greg Kroah-Hartman Link: https://lore.kernel.org/r/20240805102046.307511-5-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

serial: 8250: Move hp300_setup_serial_console() to

2024-01-28T03:01:39+00:00

If CONFIG_SERIAL_8250_HP300=y and CONFIG_SERIAL_8250_CONSOLE=y (e.g. m68k/allyesconfig): drivers/tty/serial/8250/8250_hp300.c:91:12: error: no previous prototype for ‘hp300_setup_serial_console’ [-Werror=missing-prototypes] 91 | int __init hp300_setup_serial_console(void) | ^~~~~~~~~~~~~~~~~~~~~~~~~~ Fix this by moving the existing prototype in arch/m68k/hp300/config.c to , so it is visible to both caller and implementor. While at it, provide a dummy in case CONFIG_SERIAL_8250_CONSOLE is not enabled, to reduce #ifdef clutter in the caller. Exposed by commit 0fcb70851fbfea17 ("Makefile.extrawarn: turn on missing-prototypes globally"). Signed-off-by: Geert Uytterhoeven Link: https://lore.kernel.org/r/c17469f8e47b2ef49234a85a7a14882ddf374e41.1704892597.git.geert@linux-m68k.org Signed-off-by: Greg Kroah-Hartman

Revert "8250: add support for ASIX devices with a FIFO bug"

2023-06-21T15:55:53+00:00

This reverts commit eb26dfe8aa7eeb5a5aa0b7574550125f8aa4c3b3. Commit eb26dfe8aa7e ("8250: add support for ASIX devices with a FIFO bug") merged on Jul 13, 2012 adds a quirk for PCI_VENDOR_ID_ASIX (0x9710). But that ID is the same as PCI_VENDOR_ID_NETMOS defined in 1f8b061050c7 ("[PATCH] Netmos parallel/serial/combo support") merged on Mar 28, 2005. In pci_serial_quirks array, the NetMos entry always takes precedence over the ASIX entry even since it was initially merged, code in that commit is always unreachable. In my tests, adding the FIFO workaround to pci_netmos_init() makes no difference, and the vendor driver also does not have such workaround. Given that the code was never used for over a decade, it's safe to revert it. Also, the real PCI_VENDOR_ID_ASIX should be 0x125b, which is used on their newer AX99100 PCIe serial controllers released on 2016. The FIFO workaround should not be intended for these newer controllers, and it was never implemented in vendor driver. Fixes: eb26dfe8aa7e ("8250: add support for ASIX devices with a FIFO bug") Cc: stable Signed-off-by: Jiaqing Zhao Reviewed-by: Andy Shevchenko Link: https://lore.kernel.org/r/20230619155743.827859-1-jiaqing.zhao@linux.intel.com Signed-off-by: Greg Kroah-Hartman