kernel/linux.git/Documentation/driver-api/serial, branch v6.6.132

serial: mctrl_gpio: split disable_ms into sync and no_sync APIs

2025-06-04T12:42:07+00:00

[ Upstream commit 1bd2aad57da95f7f2d2bb52f7ad15c0f4993a685 ] The following splat has been observed on a SAMA5D27 platform using atmel_serial: BUG: sleeping function called from invalid context at kernel/irq/manage.c:738 in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 27, name: kworker/u5:0 preempt_count: 1, expected: 0 INFO: lockdep is turned off. irq event stamp: 0 hardirqs last enabled at (0): [<00000000>] 0x0 hardirqs last disabled at (0): [] copy_process+0x1c4c/0x7bec softirqs last enabled at (0): [] copy_process+0x1ca0/0x7bec softirqs last disabled at (0): [<00000000>] 0x0 CPU: 0 UID: 0 PID: 27 Comm: kworker/u5:0 Not tainted 6.13.0-rc7+ #74 Hardware name: Atmel SAMA5 Workqueue: hci0 hci_power_on [bluetooth] Call trace: unwind_backtrace from show_stack+0x18/0x1c show_stack from dump_stack_lvl+0x44/0x70 dump_stack_lvl from __might_resched+0x38c/0x598 __might_resched from disable_irq+0x1c/0x48 disable_irq from mctrl_gpio_disable_ms+0x74/0xc0 mctrl_gpio_disable_ms from atmel_disable_ms.part.0+0x80/0x1f4 atmel_disable_ms.part.0 from atmel_set_termios+0x764/0x11e8 atmel_set_termios from uart_change_line_settings+0x15c/0x994 uart_change_line_settings from uart_set_termios+0x2b0/0x668 uart_set_termios from tty_set_termios+0x600/0x8ec tty_set_termios from ttyport_set_flow_control+0x188/0x1e0 ttyport_set_flow_control from wilc_setup+0xd0/0x524 [hci_wilc] wilc_setup [hci_wilc] from hci_dev_open_sync+0x330/0x203c [bluetooth] hci_dev_open_sync [bluetooth] from hci_dev_do_open+0x40/0xb0 [bluetooth] hci_dev_do_open [bluetooth] from hci_power_on+0x12c/0x664 [bluetooth] hci_power_on [bluetooth] from process_one_work+0x998/0x1a38 process_one_work from worker_thread+0x6e0/0xfb4 worker_thread from kthread+0x3d4/0x484 kthread from ret_from_fork+0x14/0x28 This warning is emitted when trying to toggle, at the highest level, some flow control (with serdev_device_set_flow_control) in a device driver. At the lowest level, the atmel_serial driver is using serial_mctrl_gpio lib to enable/disable the corresponding IRQs accordingly. The warning emitted by CONFIG_DEBUG_ATOMIC_SLEEP is due to disable_irq (called in mctrl_gpio_disable_ms) being possibly called in some atomic context (some tty drivers perform modem lines configuration in regions protected by port lock). Split mctrl_gpio_disable_ms into two differents APIs, a non-blocking one and a blocking one. Replace mctrl_gpio_disable_ms calls with the relevant version depending on whether the call is protected by some port lock. Suggested-by: Jiri Slaby Signed-off-by: Alexis Lothoré Acked-by: Richard Genoud Link: https://lore.kernel.org/r/20250217-atomic_sleep_mctrl_serial_gpio-v3-1-59324b313eef@bootlin.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

Documentation: driver-api: correct spelling

2023-02-02T18:05:16+00:00

Correct spelling problems for Documentation/driver-api/ as reported by codespell. Signed-off-by: Randy Dunlap Cc: Mauro Carvalho Chehab Cc: linux-media@vger.kernel.org Cc: Vishal Verma Cc: Dave Jiang Cc: nvdimm@lists.linux.dev Cc: Vinod Koul Cc: dmaengine@vger.kernel.org Cc: linux-raid@vger.kernel.org Cc: linux-usb@vger.kernel.org Acked-by: Dan Williams Acked-by: Song Liu Acked-by: Greg Kroah-Hartman Link: https://lore.kernel.org/r/20230129231053.20863-3-rdunlap@infradead.org Signed-off-by: Jonathan Corbet

Documentation: Make formatting consistent for rs485 docs

2022-11-03T02:43:05+00:00

Tweak styling of names that come directly from the code. Suggested-by: Bagas Sanjaya Reviewed-by: Bagas Sanjaya Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20221019093343.9546-6-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman

Documentation: rs485: Fix struct referencing

2022-11-03T02:43:05+00:00

Use "struct serial_rs485" to get the references properly recognized. Reviewed-by: Andy Shevchenko Reviewed-by: Bagas Sanjaya Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20221019093343.9546-5-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman

Documentation: rs485: Mention uart_get_rs485_mode()

2022-11-03T02:43:05+00:00

Add to rs485 documentation that serial core prepares the struct serial_rs485 when uart_get_rs485_mode() is called. Remove the wrong claim that the driver must fill it by itself. Reviewed-by: Andy Shevchenko Reviewed-by: Bagas Sanjaya Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20221019093343.9546-4-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman

Documentation: rs485: Link reference properly

2022-11-03T02:43:05+00:00

Link DT bindings reference properly. Reviewed-by: Andy Shevchenko Reviewed-by: Bagas Sanjaya Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20221019093343.9546-3-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman

serial: Convert serial_rs485 to kernel doc

2022-11-03T02:43:05+00:00

Convert struct serial_rs485 comments to kernel doc format and include it into documentation. Suggested-by: Andy Shevchenko Reviewed-by: Andy Shevchenko Reviewed-by: Bagas Sanjaya Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20221019093343.9546-2-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman

tty: serial: introduce transmit helpers

2022-11-03T02:32:40+00:00

Many serial drivers do the same thing: * send x_char if set * keep sending from the xmit circular buffer until either - the loop reaches the end of the xmit buffer - TX is stopped - HW fifo is full * check for pending characters and: - wake up tty writers to fill for more data into xmit buffer - stop TX if there is nothing in the xmit buffer The only differences are: * how to write the character to the HW fifo * the check of the end condition: - is the HW fifo full? - is limit of the written characters reached? So unify the above into two helpers: * uart_port_tx_limited() -- it performs the above taking the written characters limit into account, and * uart_port_tx() -- the same as above, except it only checks the HW readiness, not the characters limit. The HW specific operations (as stated as "differences" above) are passed as arguments to the macros. They are: * tx_ready -- returns true if HW can accept more data. * put_char -- write a character to the device. * tx_done -- when the write loop is done, perform arbitrary action before potential invocation of ops->stop_tx() happens. Note that the above are macros. This means the code is generated in place and the above 3 arguments are "inlined". I.e. no added penalty by generating call instructions for every single character. Nor any indirect calls. (As in some previous versions of this patchset.) Reviewed-by: Ilpo Järvinen Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20221004104927.14361-2-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: serial: document uart_get_console()

2022-07-28T08:37:42+00:00

This was the only function mentioned in the text, but was neither linked nor documented. So document and link it, so that hyperlinking works in the text. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20220728061056.20799-6-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

tty: serial: serial_core, reformat kernel-doc for functions

2022-07-28T08:37:42+00:00

There are many annotated functions in serial_core.c, but they do not completely conform to the kernel-doc style. So reformat them and link them from the Documentation. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20220728061056.20799-5-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman