linux-toradex.git/include/linux/serial_8250.h, branch v6.0-rc1

serial: 8250: create lsr_save_mask

2022-06-27T12:44:20+00:00

Allow drivers to alter LSR save mask.

Reviewed-by: Andy Shevchenko 
Signed-off-by: Ilpo Järvinen 
Link: https://lore.kernel.org/r/20220624204210.11112-3-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250: make saved LSR larger

2022-06-27T12:44:20+00:00

DW flags address received as BIT(8) in LSR. In order to not lose that
on read, enlarge lsr_saved_flags to u16.

Adjust lsr/status variables and related call chains to use u16.
Technically, some of these type conversion would not be needed but it
doesn't hurt to be consistent.

Signed-off-by: Ilpo Järvinen 
Link: https://lore.kernel.org/r/20220624204210.11112-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250: Move Alpha-specific quirk out of the core

2021-12-30T12:23:44+00:00

struct uart_8250_port contains mcr_mask and mcr_force members whose
sole purpose is to work around an Alpha-specific quirk.  This code
doesn't belong in the core where it is executed by everyone else,
so move it to a proper ->set_mctrl callback which is used on the
affected Alpha machine only.

The quirk was introduced in January 1995:
https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/diff/drivers/char/serial.c?h=1.1.83

The members in struct uart_8250_port were added in 2002:
https://git.kernel.org/history/history/c/4524aad27854

The quirk applies to non-PCI Alphas and arch/alpha/Kconfig specifies
"select FORCE_PCI if !ALPHA_JENSEN".  So apparently the only affected
machine is the EISA-based Jensen that Linus was working on back then:
https://lore.kernel.org/all/CAHk-=wj1JWZ3sCrGz16nxEj7=0O+srMg6Ah3iPTDXSPKEws_SA@mail.gmail.com/

Up until now the quirk is not applied unless CONFIG_PCI is disabled.
If users forget to do that or run a generic Alpha kernel, the serial
ports aren't usable on Jensen.  Avoid by confining the quirk to
CONFIG_ALPHA_JENSEN instead of !CONFIG_PCI.  On generic Alpha kernels,
auto-detect at runtime whether the quirk needs to be applied.

Cc: Russell King 
Cc: Ulrich Teichert 
Cc: Linus Torvalds 
Signed-off-by: Lukas Wunner 
Link: https://lore.kernel.org/r/b83d069cb516549b8a5420e097bb6bdd806f36fc.1640695609.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman

tty/serial: make port of serial8250_register_8250_port const

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

After the previous patch, we can make port passed to
serial8250_find_match_or_unused const. And then we can make const also
port of serial8250_register_8250_port.

Signed-off-by: Jiri Slaby 
Link: https://lore.kernel.org/r/20210519072153.3859-2-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman

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