linux-stable.git/include/linux/serial_core.h, branch v5.15.208

serial: core: fix kernel-doc for uart_port_unlock_irqrestore()

2024-05-02T14:24:50+00:00

commit 29bff582b74ed0bdb7e6986482ad9e6799ea4d2f upstream.

Fix the function name to avoid a kernel-doc warning:

include/linux/serial_core.h:666: warning: expecting prototype for uart_port_lock_irqrestore(). Prototype was for uart_port_unlock_irqrestore() instead

Fixes: b0af4bcb4946 ("serial: core: Provide port lock wrappers")
Signed-off-by: Randy Dunlap 
Cc: Thomas Gleixner 
Cc: John Ogness 
Cc: linux-serial@vger.kernel.org
Cc: Greg Kroah-Hartman 
Cc: Jiri Slaby 
Reviewed-by: John Ogness 
Link: https://lore.kernel.org/r/20230927044128.4748-1-rdunlap@infradead.org
Signed-off-by: Greg Kroah-Hartman

serial: core: Provide port lock wrappers

2024-05-02T14:24:47+00:00

[ Upstream commit b0af4bcb49464c221ad5f95d40f2b1b252ceedcc ]

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.

Provide wrapper functions for spin_[un]lock*(port->lock) invocations so
that the console mechanics can be applied later on at a single place and
does not require to copy the same logic all over the drivers.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Ilpo Järvinen 
Signed-off-by: John Ogness 
Link: https://lore.kernel.org/r/20230914183831.587273-2-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman 
Stable-dep-of: 54c4ec5f8c47 ("serial: mxs-auart: add spinlock around changing cts state")
Signed-off-by: Sasha Levin

serial: Add rs485_supported to uart_port

2022-12-02T16:40:59+00:00

[ Upstream commit 8925c31c1ac2f1e05da988581f2a70a2a8c4d638 ]

Preparing to move serial_rs485 struct sanitization into serial core,
each driver has to provide what fields/flags it supports. This
information is pointed into by rs485_supported.

Signed-off-by: Ilpo Järvinen 
Link: https://lore.kernel.org/r/20220606100433.13793-4-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman 
Stable-dep-of: 76bad3f88750 ("tty: serial: fsl_lpuart: don't break the on-going transfer when global reset")
Signed-off-by: Sasha Levin

serial: 8250: Let drivers request full 16550A feature probing

2022-10-26T10:34:24+00:00

commit 9906890c89e4dbd900ed87ad3040080339a7f411 upstream.

A SERIAL_8250_16550A_VARIANTS configuration option has been recently
defined that lets one request the 8250 driver not to probe for 16550A
device features so as to reduce the driver's device startup time in
virtual machines.

Some actual hardware devices require these features to have been fully
determined however for their driver to work correctly, so define a flag
to let drivers request full 16550A feature probing on a device-by-device
basis if required regardless of the SERIAL_8250_16550A_VARIANTS option
setting chosen.

Fixes: dc56ecb81a0a ("serial: 8250: Support disabling mdelay-filled probes of 16550A variants")
Cc: stable@vger.kernel.org # v5.6+
Reported-by: Anders Blomdell 
Signed-off-by: Maciej W. Rozycki 
Link: https://lore.kernel.org/r/alpine.DEB.2.21.2209202357520.41633@angie.orcam.me.uk
Signed-off-by: Greg Kroah-Hartman

serial: Create uart_xmit_advance()

2022-09-28T09:11:54+00:00

commit e77cab77f2cb3a1ca2ba8df4af45bb35617ac16d upstream.

A very common pattern in the drivers is to advance xmit tail
index and do bookkeeping of Tx'ed characters. Create
uart_xmit_advance() to handle it.

Reviewed-by: Andy Shevchenko 
Cc: stable 
Signed-off-by: Ilpo Järvinen 
Link: https://lore.kernel.org/r/20220901143934.8850-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250: Fix PM usage_count for console handover

2022-07-21T19:24:43+00:00

commit f9b11229b79c0fb2100b5bb4628a101b1d37fbf6 upstream.

When console is enabled, univ8250_console_setup() calls
serial8250_console_setup() before .dev is set to uart_port. Therefore,
it will not call pm_runtime_get_sync(). Later, when the actual driver
is going to take over univ8250_console_exit() is called. As .dev is
already set, serial8250_console_exit() makes pm_runtime_put_sync() call
with usage count being zero triggering PM usage count warning
(extra debug for univ8250_console_setup(), univ8250_console_exit(), and
serial8250_register_ports()):

[    0.068987] univ8250_console_setup ttyS0 nodev
[    0.499670] printk: console [ttyS0] enabled
[    0.717955] printk: console [ttyS0] printing thread started
[    1.960163] serial8250_register_ports assigned dev for ttyS0
[    1.976830] printk: console [ttyS0] disabled
[    1.976888] printk: console [ttyS0] printing thread stopped
[    1.977073] univ8250_console_exit ttyS0 usage:0
[    1.977075] serial8250 serial8250: Runtime PM usage count underflow!
[    1.977429] dw-apb-uart.6: ttyS0 at MMIO 0x4010006000 (irq = 33, base_baud = 115200) is a 16550A
[    1.977812] univ8250_console_setup ttyS0 usage:2
[    1.978167] printk: console [ttyS0] printing thread started
[    1.978203] printk: console [ttyS0] enabled

To fix the issue, call pm_runtime_get_sync() in
serial8250_register_ports() as soon as .dev is set for an uart_port
if it has console enabled.

This problem became apparent only recently because 82586a721595 ("PM:
runtime: Avoid device usage count underflows") added the warning
printout. I confirmed this problem also occurs with v5.18 (w/o the
warning printout, obviously).

Fixes: bedb404e91bb ("serial: 8250_port: Don't use power management for kernel console")
Cc: stable 
Tested-by: Tony Lindgren 
Reviewed-by: Andy Shevchenko 
Reviewed-by: Tony Lindgren 
Signed-off-by: Ilpo Järvinen 
Link: https://lore.kernel.org/r/b4f428e9-491f-daf2-2232-819928dc276e@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250: fix XOFF/XON sending when DMA is used

2022-04-08T12:23:50+00:00

[ Upstream commit f58c252e30cf74f68b0054293adc03b5923b9f0e ]

When 8250 UART is using DMA, x_char (XON/XOFF) is never sent
to the wire. After this change, x_char is injected correctly.

Create uart_xchar_out() helper for sending the x_char out and
accounting related to it. It seems that almost every driver
does these same steps with x_char. Except for 8250, however,
almost all currently lack .serial_out so they cannot immediately
take advantage of this new helper.

The downside of this patch is that it might reintroduce
the problems some devices faced with mixed DMA/non-DMA transfer
which caused revert f967fc8f165f (Revert "serial: 8250_dma:
don't bother DMA with small transfers"). However, the impact
should be limited to cases with XON/XOFF (that didn't work
with DMA capable devices to begin with so this problem is not
very likely to cause a major issue, if any at all).

Fixes: 9ee4b83e51f74 ("serial: 8250: Add support for dmaengine")
Reported-by: Gilles Buloz 
Tested-by: Gilles Buloz 
Reviewed-by: Andy Shevchenko 
Signed-off-by: Ilpo Järvinen 
Link: https://lore.kernel.org/r/20220314091432.4288-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Sasha Levin

serial: 8250: fix handle_irq locking

2021-07-21T10:53:26+00:00

The 8250 handle_irq callback is not just called from the interrupt
handler but also from a timer callback when polling (e.g. for ports
without an interrupt line). Consequently the callback must explicitly
disable interrupts to avoid a potential deadlock with another interrupt
in polled mode.

Add back an irqrestore-version of the sysrq port-unlock helper and use
it in the 8250 callbacks that need it.

Fixes: 75f4e830fa9c ("serial: do not restore interrupt state in sysrq helper")
Cc: stable@vger.kernel.org	# 5.13
Cc: Joel Stanley 
Cc: Andrew Jeffery 
Reported-by: kernel test robot 
Signed-off-by: Johan Hovold 
Link: https://lore.kernel.org/r/20210714080427.28164-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman

tty/serial: clean up uart_match_port

2021-05-20T14:59:14+00:00

* make parameters const (as they are only read)
* return bool (as comparison results are returned)
* add \n before final return

Signed-off-by: Jiri Slaby 
Link: https://lore.kernel.org/r/20210519072153.3859-1-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman

tty: cumulate and document tty_struct::flow* members

2021-05-13T14:57:16+00:00

Group the flow flags under a single struct called flow. The new struct
contains 'stopped' and 'tco_stopped' bools which used to be bits in a
bitfield. The struct also contains the lock protecting them to
potentially share the same cache line.

Note that commit c545b66c6922b (tty: Serialize tcflow() with other tty
flow control changes) added a padding to the original bitfield. It was
for the bitfield to occupy a whole 64b word to avoid interferring stores
on Alpha (cannot we evaporate this arch with weird implications to C
code yet?). But it doesn't work as expected as the padding
(tty_struct::unused) is aligned to a 8B boundary too and occupies some
bytes from the next word.

So make it reliable by:
1) setting __aligned of the struct -- that aligns the start, and
2) making 'unsigned long unused[0]' as the last member of the struct --
   pads the end.

This is also the perfect time to start the documentation of tty_struct
where all this lives. So we start by documenting what these bools
actually serve for. And why we do all the alignment dances. Only the few
up-to-date information from the Theodore's comment made it into this new
Kerneldoc comment.

Signed-off-by: Jiri Slaby 
Cc: "David S. Miller" 
Cc: Jakub Kicinski 
Cc: Jonathan Corbet 
Cc: Arnd Bergmann 
Cc: Ulf Hansson 
Cc: Heiko Carstens 
Cc: Vasily Gorbik 
Cc: Christian Borntraeger 
Cc: Shawn Guo 
Cc: Sascha Hauer 
Cc: Vineet Gupta 
Cc: "Maciej W. Rozycki" 
Link: https://lore.kernel.org/r/20210505091928.22010-13-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman