linux-toradex.git/include/linux/serial_8250.h, branch v5.12-rc6

tty: serial: 8250: 8250_port: Move prototypes to shared location

2020-11-13T14:28:12+00:00

Fixes the following W=1 kernel build warning(s):

 drivers/tty/serial/8250/8250_port.c:349:14: warning: no previous prototype for ‘au_serial_in’ [-Wmissing-prototypes]
 drivers/tty/serial/8250/8250_port.c:359:6: warning: no previous prototype for ‘au_serial_out’ [-Wmissing-prototypes]

Cc: Greg Kroah-Hartman 
Cc: Jiri Slaby 
Cc: Mike Hudson 
Cc: linux-serial@vger.kernel.org
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20201112105857.2078977-3-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman

serial: 8250: Add 8250 port clock update method

2020-07-29T15:14:38+00:00

Some platforms can be designed in a way so the UART port reference clock
might be asynchronously changed at some point. In Baikal-T1 SoC this may
happen due to the reference clock being shared between two UART ports, on
the Allwinner SoC the reference clock is derived from the CPU clock, so
any CPU frequency change should get to be known/reflected by/in the UART
controller as well. But it's not enough to just update the
uart_port->uartclk field of the corresponding UART port, the 8250
controller reference clock divisor should be altered so to preserve
current baud rate setting. All of these things is done in a coherent
way by calling the serial8250_update_uartclk() method provided in this
patch. Though note that it isn't supposed to be called from within the
UART port callbacks because the locks using to the protect the UART port
data are already taken in there.

Signed-off-by: Serge Semin 

Link: https://lore.kernel.org/r/20200723003357.26897-2-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Greg Kroah-Hartman

serial: 8250_port: Don't use power management for kernel console

2020-03-17T14:58:00+00:00

Doing any kind of power management for kernel console is really bad idea.

First of all, it runs in poll and atomic mode. This fact attaches a limitation
on the functions that might be called. For example, pm_runtime_get_sync() might
sleep and thus can't be used. This call needs, for example, to bring the device
to powered on state on the system, where the power on sequence may require
on-atomic operations, such as Intel Cherrytrail with ACPI enumerated UARTs.
That said, on ACPI enabled platforms it might even call firmware for a job.

On the other hand pm_runtime_get() doesn't guarantee that device will become
powered on fast enough.

Besides that, imagine the case when console is about to print a kernel Oops and
it's powered off. In such an emergency case calling the complex functions is
not the best what we can do, taking into consideration that user wants to see
at least something of the last kernel word before it passes away.

Here we modify the 8250 console code to prevent runtime power management.

Note, there is a behaviour change for OMAP boards. It will require to detach
kernel console to become idle.

Link: https://lists.openwall.net/linux-kernel/2018/09/29/65
Suggested-by: Russell King 
Signed-off-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20200217114016.49856-6-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250: Generalize rs485 software emulation

2020-03-07T08:52:02+00:00

Commit e490c9144cfa ("tty: Add software emulated RS485 support for 8250")
introduced support to use RTS as an rs485 Transmit Enable signal.
So far the only drivers taking advantage of it are 8250_omap.c and
8250_of.c.

We're about to make use of the feature in 8250_bcm2835aux.c as well.
The bcm2835aux differs from omap chips by inverting the meaning of RTS
in the MCR register.  Moreover, omap achieves half-duplex mode by
disabling the RX interrupt and clearing the RX FIFO when TX stops.
The bcm2835aux requires disabling the receiver instead.

Support these behavioral differences by generalizing the rs485 emulation:
Introduce ->rs485_start_tx() and ->rs485_stop_tx() callbacks in struct
uart_8250_port, provide generic implementations containing the existing
code and use them as callbacks in 8250_omap.c and 8250_of.c.

start_tx_rs485() is idempotent in that it recognizes whether RTS is
already asserted.  Achieve the same by introducing a tx_stopped flag in
struct uart_8250_em485.  This may even perform a little better on arches
where memory access is faster than mmio access.

Signed-off-by: Lukas Wunner 
Cc: Matwey V. Kornilov 
Link: https://lore.kernel.org/r/5ac0464ae4414708e723a1e0d52b0c1b2bd41b9b.1582895077.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman

tty/serial: Migrate 8250_fsl to use has_sysrq

2019-12-18T14:04:42+00:00

The SUPPORT_SYSRQ ifdeffery is not nice as:
- May create misunderstanding about sizeof(struct uart_port) between
  different objects
- Prevents moving functions from serial_core.h
- Reduces readability (well, it's ifdeffery - it's hard to follow)

In order to remove SUPPORT_SYSRQ, has_sysrq variable has been added.
Initialise it in driver's probe and remove ifdeffery.

In contrast to 8250/8250_of, legacy_serial on powerpc does fill
(struct plat_serial8250_port). The reason is likely that it's done on
device_initcall(), not on probe. So, 8250_core is not yet probed.

Propagate value from platform_device on 8250 probe - in case powepc
legacy driver it's initialized on initcall, in case 8250_of it will be
initialized later on of_platform_serial_setup().

Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Michael Ellerman 
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Dmitry Safonov 
Link: https://lore.kernel.org/r/20191213000657.931618-6-dima@arista.com
Signed-off-by: Greg Kroah-Hartman

tty/serial/8250: use mctrl_gpio helpers

2019-06-21T08:18:43+00:00

This patch permits the usage for GPIOs to control
the CTS/RTS/DTR/DSR/DCD/RI signals.

Changed by Stefan:
Only call mctrl_gpio_init(), if the device has no ACPI companion device
to not break existing ACPI based systems. Also only use the mctrl_gpio_
functions when "gpios" is available.

Use MSR / MCR <-> TIOCM wrapper functions.

Signed-off-by: Yegor Yefremov 
Signed-off-by: Stefan Roese 
Reviewed-by: Andy Shevchenko 
Reviewed-by: Mika Westerberg 
Tested-by: Yegor Yefremov 
Cc: Mika Westerberg 
Cc: Andy Shevchenko 
Cc: Giulio Benetti 
Cc: Yegor Yefremov 
Cc: Greg Kroah-Hartman 
Signed-off-by: Greg Kroah-Hartman

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

2019-05-30T18:26:32+00:00

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 of the license or at
  your option any later version

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 3029 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Allison Randal 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman

serial: 8250: Rate limit serial port rx interrupts during input overruns

2018-12-17T15:02:57+00:00

When a serial port gets faulty or gets flooded with inputs, its interrupt
handler starts to work double time to get the characters to the workqueue
for the tty layer to handle them. When this busy time on the serial/tty
subsystem happens during boot, where it is also busy on the userspace
trying to initialise, some processes can continuously get preempted
and will be on hold until the interrupts subside.

The fix is to backoff on processing received characters for a specified
amount of time when an input overrun is seen (received a new character
before the previous one is processed). This only stops receive and will
continue to transmit characters to serial port. After the backoff period
is done, it receive will be re-enabled. This is optional and will only
be enabled by setting 'overrun-throttle-ms' in the dts.

Signed-off-by: Darwin Dingel 
Signed-off-by: Greg Kroah-Hartman

serial: 8250: export serial8250_do_set_divisor()

2018-07-12T15:07:26+00:00

Some drivers could call serial8250_do_set_divisor() to complete its
own set_divisor routine. Export this symbol for code reusing.

Signed-off-by: Jisheng Zhang 
Reviewed-by: Andy Shevchenko 
Signed-off-by: Greg Kroah-Hartman

serial/8250: export serial8250_read_char

2018-04-23T08:16:50+00:00

Currently, we export serial8250_rx_chars, which does a whole bunch of
reads from the 8250 data register, without any form of flow control
between reads.

An upcoming change to the aspeed vuart driver implements more
fine-grained flow control in the interrupt handler, requiring
character-at-a-time control over the rx path.

This change exports serial8250_read_char to allow this.

Signed-off-by: Jeremy Kerr 
Tested-by: Eddie James 
Tested-by: Joel Stanley 
Signed-off-by: Greg Kroah-Hartman