serial: mctrl_gpio: split disable_ms into sync and no_sync APIs

The following splat has been observed on a SAMA5D27 platform using
atmel_serial:

BUG: sleeping function called from invalid context a

serial: mctrl_gpio: split disable_ms into sync and no_sync APIs

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): [<c01588f0>] copy_process+0x1c4c/0x7bec
softirqs last enabled at (0): [<c0158944>] 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 <[email protected]>
Signed-off-by: Alexis Lothoré <[email protected]>
Acked-by: Richard Genoud <[email protected]>
Link: https://lore.kernel.org/r/20250217-atomic_sleep_mctrl_serial_gpio-v3-1-59324b313eef@bootlin.com
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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serial: mctrl_gpio: Remove unused mctrl_gpio_free

mctrl_gpio_free() was added in 2014 by
commit 84130aace839 ("tty/serial: Add GPIOLIB helpers for controlling
modem lines")

It does have a comment s

serial: mctrl_gpio: Remove unused mctrl_gpio_free

mctrl_gpio_free() was added in 2014 by
commit 84130aace839 ("tty/serial: Add GPIOLIB helpers for controlling
modem lines")

It does have a comment saying:
'- * Normally, this function will not be called, as the GPIOs will
- * be disposed of by the resource management code.'

indeed, it doesn't seem to have been used since it was added.

Remove it.

Signed-off-by: Dr. David Alan Gilbert <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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Documentation: driver-api: correct spelling

Correct spelling problems for Documentation/driver-api/ as reported
by codespell.

Signed-off-by: Randy Dunlap <[email protected]>
Cc: Mauro Carvalho

Documentation: driver-api: correct spelling

Correct spelling problems for Documentation/driver-api/ as reported
by codespell.

Signed-off-by: Randy Dunlap <[email protected]>
Cc: Mauro Carvalho Chehab <[email protected]>
Cc: [email protected]
Cc: Vishal Verma <[email protected]>
Cc: Dave Jiang <[email protected]>
Cc: [email protected]
Cc: Vinod Koul <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Acked-by: Dan Williams <[email protected]>
Acked-by: Song Liu <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jonathan Corbet <[email protected]>

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tty: serial: introduce transmit helpers

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

tty: serial: introduce transmit helpers

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 <[email protected]>
Signed-off-by: Jiri Slaby (SUSE) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: serial: document uart_get_console()

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.

Si

tty: serial: document uart_get_console()

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 <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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

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

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

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 <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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Documentation: serial: link uart_ops properly

The syntax to reference a struct in text is "struct XY". So reference
uart_ops properly, so that hyperlinks work.

Signed-off-by: Jiri Slaby <jslaby@sus

Documentation: serial: link uart_ops properly

The syntax to reference a struct in text is "struct XY". So reference
uart_ops properly, so that hyperlinks work.

Signed-off-by: Jiri Slaby <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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Documentation: serial: move GPIO kernel-doc to the functions

The GPIO uart functions are documented in Documentation. Move and
transform this documentation into kernel-doc directly in the code and
r

Documentation: serial: move GPIO kernel-doc to the functions

The GPIO uart functions are documented in Documentation. Move and
transform this documentation into kernel-doc directly in the code and
reference it in Documentation using kernel-doc:.

This makes it easier to update, maintain and check by the build.

Signed-off-by: Jiri Slaby <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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Documentation: serial: dedup kernel-doc for uart functions

Some of the serial (uart_*) functions are documented twice. Once as
kernel-doc along their sources and once in Documentation. So deduplicat

Documentation: serial: dedup kernel-doc for uart functions

Some of the serial (uart_*) functions are documented twice. Once as
kernel-doc along their sources and once in Documentation. So deduplicate
these texts, merge them into kernel-doc in the sources, and link them
using kernel-doc: from the Documentation.

To be properly linked and rendered, tabulators had to be removed from
the comments.

Signed-off-by: Jiri Slaby <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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Documentation: serial: move uart_ops documentation to the struct

While it's a lot of text, it always helps to keep it up to date when
it's by the source. (And not in a separate file.)

The documenta

Documentation: serial: move uart_ops documentation to the struct

While it's a lot of text, it always helps to keep it up to date when
it's by the source. (And not in a separate file.)

The documentation tooling also makes sure that all members of the
structure are documented. (If not, it complains loudly.)

Finally, there needs to be no comments inlined in the structure, so they
are dropped as they are superfluous now.

The compilation time of this header (tested with serial_core.c) didn't
change in my testing at all.

Signed-off-by: Jiri Slaby <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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serial: Support for RS-485 multipoint addresses

Add support for RS-485 multipoint addressing using 9th bit [*]. The
addressing mode is configured through ->rs485_config().

ADDRB in termios indicate

serial: Support for RS-485 multipoint addresses

Add support for RS-485 multipoint addressing using 9th bit [*]. The
addressing mode is configured through ->rs485_config().

ADDRB in termios indicates 9th bit addressing mode is enabled. In this
mode, 9th bit is used to indicate an address (byte) within the
communication line. ADDRB can only be enabled/disabled through
->rs485_config() that is also responsible for setting the destination and
receiver (filter) addresses.

Add traps to detect unwanted changes to struct serial_rs485 layout using
static_assert().

[*] Technically, RS485 is just an electronic spec and does not itself
specify the 9th bit addressing mode but 9th bit seems at least
"semi-standard" way to do addressing with RS485.

Signed-off-by: Ilpo Järvinen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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serial: Drop timeout from uart_port

Since commit 31f6bd7fad3b ("serial: Store character timing information
to uart_port"), per frame timing information is available on uart_port.
Uart port's timeout

serial: Drop timeout from uart_port

Since commit 31f6bd7fad3b ("serial: Store character timing information
to uart_port"), per frame timing information is available on uart_port.
Uart port's timeout can be derived from frame_time by multiplying with
fifosize.

Most callers of uart_poll_timeout are not made under port's lock. To be
on the safe side, make sure frame_time is only accessed once. As
fifo_size is effectively a constant, it shouldn't cause any issues.

Signed-off-by: Ilpo Järvinen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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Documentation: move tty to driver-api

Based on discussion starting as [email protected], let's move
the tty documentation to driver-api. It's more appropriate there.

Cc: Jonathan Corbet <

Documentation: move tty to driver-api

Based on discussion starting as [email protected], let's move
the tty documentation to driver-api. It's more appropriate there.

Cc: Jonathan Corbet <[email protected]>
Signed-off-by: Jiri Slaby <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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docs: serial: fix a reference file name in driver.rst

Fix the following 'make refcheckdocs' warning:
Warning: Documentation/driver-api/serial/driver.rst references a file
that doesn't exist: Documen

docs: serial: fix a reference file name in driver.rst

Fix the following 'make refcheckdocs' warning:
Warning: Documentation/driver-api/serial/driver.rst references a file
that doesn't exist: Documentation/driver-api/serial/tty.rst

Signed-off-by: Wan Jiabing <[email protected]>
Reviewed-by: Jiri Slaby <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jonathan Corbet <[email protected]>

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docs: serial: move it to the driver-api

The contents of this directory is mostly driver-api stuff.

Signed-off-by: Mauro Carvalho Chehab <[email protected]>