Fix the port-lock initialisation regression introduced by commit
a3cb39d258 ("serial: core: Allow detach and attach serial device for
console") by making sure that the lock is again initialised during
console setup.
The console may be registered before the serial controller has been
probed in which case the port lock needs to be initialised during
console setup by a call to uart_set_options(). The console-detach
changes introduced a regression in several drivers by effectively
removing that initialisation by not initialising the lock when the port
is used as a console (which is always the case during console setup).
Add back the early lock initialisation and instead use a new
console-reinit flag to handle the case where a console is being
re-attached through sysfs.
The question whether the console-detach interface should have been added
in the first place is left for another discussion.
Note that the console-enabled check in uart_set_options() is not
redundant because of kgdboc, which can end up reinitialising an already
enabled console (see commit 42b6a1baa3 ("serial_core: Don't
re-initialize a previously initialized spinlock.")).
Fixes: a3cb39d258 ("serial: core: Allow detach and attach serial device for console")
Cc: stable <stable@vger.kernel.org> # 5.7
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200909143101.15389-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit f743061a85 ("serial: core: Initialise spin lock before use in
uart_configure_port()") tried to work around a breakage introduced by
commit a3cb39d258 ("serial: core: Allow detach and attach serial
device for console") by adding a second initialisation of the port lock
when registering the port.
As reported by the build robots [1], this doesn't really solve the
regression introduced by the console-detach changes and also adds a
second redundant initialisation of the lock for normal ports.
Start cleaning up this mess by removing the redundant initialisation and
making sure that the port lock is again initialised once-only for ports
that aren't already in use as a console.
[1] https://lore.kernel.org/r/20200802054852.GR23458@shao2-debian
Fixes: f743061a85 ("serial: core: Initialise spin lock before use in uart_configure_port()")
Fixes: a3cb39d258 ("serial: core: Allow detach and attach serial device for console")
Cc: stable <stable@vger.kernel.org> # 5.7
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200909143101.15389-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit c5cbc78acf ("tty: serial: qcom_geni_serial: Initialize baud
in qcom_geni_console_setup") fixed a bug by initting a variable that
was used in some cases without initialization. However, the "default"
baud rate picked by that CL was probably not the best choice. The
chances that anyone out there is trying to run a system with kernel
messages piped out over a 9600 baud serial port is just about nil.
Console messages are printed in a blocking manner. At 9600 baud we
print about 1 character per millisecond which means that printing a
40-byte message to the console will take ~40 ms. While it would
probably work, it's going to make boot _very_ slow and probably cause
the occasional timeout here and there in drivers (heck, even at 115200
console delays can wreck havoc).
This has already bit at least two people that I'm aware of that tried
to enable serial console by just adding "console=ttyMSM0" (instead of
"console=ttyMSM0,115200n8") to the command line, so it seems like it'd
be nice to fix.
Let's switch the default to 115200.
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Akash Asthana <akashast@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20200911080054.1.I4c00b921c2f17b6988688046fa7be0f729f8d591@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Samsung S3C24xx and S3C64xx machine code cleanup for v5.10
Big cleanup for the Samsung S3C24xx and S3C64xx platforms, although it
also touches files shared with S5Pv210 and Exynos. This is mostly Arnd
Bergmann work which Krzysztof Kozlowski took over, rebased and polished.
The goal is to cleanup, merge and finally make the Samsung S3C24xx and
S3C64xx architectures multiplatform. The multiplatform did not happen
yet here - just cleaning up and merging into one arch/arm/mach-s3c
directory. However this is step forward for multiplatform or at least
to keep this code still maintainable.
This pulls also branch with changes for Samsung SoC sound drivers from
broonie/sound because the cleanups there were part of this series and
all further patches depend on them.
* tag 'samsung-soc-s3c-5.10' of https://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux: (62 commits)
ARM: s3c: Avoid naming clash of S3C24xx and S3C64xx timer setup
ARM: s3c: Cleanup from old plat-samsung include
ARM: s3c: make headers local if possible
ARM: s3c: move into a common directory
ARM: s3c24xx: stop including mach/hardware.h from mach/io.h
cpufreq: s3c24xx: move low-level clk reg access into platform code
cpufreq: s3c2412: use global s3c2412_cpufreq_setrefresh
ARM: s3c: remove cpufreq header dependencies
cpufreq: s3c24xx: split out registers
fbdev: s3c2410fb: remove mach header dependency
ARM: s3c24xx: bast: avoid irq_desc array usage
ARM: s3c24xx: spi: avoid hardcoding fiq number in driver
ARM: s3c24xx: include mach/irqs.h where needed
ARM: s3c24xx: move s3cmci pinctrl handling into board files
ARM: s3c24xx: move iis pinctrl config into boards
ARM: s3c24xx: move spi fiq handler into platform
ARM: s3c: adc: move header to linux/soc/samsung
ARM: s3c24xx: move irqchip driver back into platform
ARM: s3c24xx: move regs-spi.h into spi driver
ARM: s3c64xx: remove mach/hardware.h
...
Link: https://lore.kernel.org/r/20200831154751.7551-1-krzk@kernel.org
Signed-off-by: Olof Johansson <olof@lixom.net>
SB1250 uart bug is related to PASS 2 workarounds. Use config
CONFIG_SB1_PASS_2_WORKAROUNDS directly and get rid of SIBYTE_1956_WAR.
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
parse_options() in drivers/tty/serial/earlycon.c calls uart_parse_earlycon
in drivers/tty/serial/serial_core.c therefore selecting SERIAL_EARLYCON
should automatically select SERIAL_CORE, otherwise will result in symbol
not found error during linking if SERIAL_CORE is not configured as builtin
Fixes: 9aac588759 ("tty/serial: add generic serial earlycon")
Signed-off-by: Tong Zhang <ztong0001@gmail.com>
Link: https://lore.kernel.org/r/20200828123949.2642-1-ztong0001@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Some derivates of sc16is7xx devices expose more than one tty device to
userspace. If multiple such devices exist in a system, userspace
currently has no clean way to infer which tty maps to which physical
line.
Set the .iobase value to the relative index within the device to allow
infering the order through sysfs.
Signed-off-by: Daniel Mack <daniel@zonque.org>
Link: https://lore.kernel.org/r/20200901120329.4176302-1-daniel@zonque.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
As per the documentation (Documentation/filesystems/sysfs.rst),
snprintf() should not be used for formatting values returned by sysfs.
For all of the instances in serial_core.c, we know that the string will
be <PAGE_SIZE in length, so just use sprintf().
Issue identified by Coccinelle.
Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
Link: https://lore.kernel.org/r/20200824223932.27709-1-alex.dewar90@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Pull tty/serial fixes from Greg KH:
"Here are a few small TTY/Serial/vt fixes for 5.9-rc3
Included in here are:
- qcom serial fixes
- vt ioctl and core bugfixes
- pl011 serial driver fixes
- 8250 serial driver fixes
- other misc serial driver fixes
and for good measure:
- fbcon fix for syzbot found problem.
All of these have been in linux-next for a while with no reported
issues"
* tag 'tty-5.9-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
tty: serial: imx: add dependence and build for earlycon
serial: samsung: Removes the IRQ not found warning
serial: 8250: change lock order in serial8250_do_startup()
serial: stm32: avoid kernel warning on absence of optional IRQ
serial: pl011: Fix oops on -EPROBE_DEFER
serial: pl011: Don't leak amba_ports entry on driver register error
serial: 8250_exar: Fix number of ports for Commtech PCIe cards
tty: serial: qcom_geni_serial: Drop __init from qcom_geni_console_setup
serial: qcom_geni_serial: Fix recent kdb hang
vt_ioctl: change VT_RESIZEX ioctl to check for error return from vc_resize()
fbcon: prevent user font height or width change from causing potential out-of-bounds access
vt: defer kfree() of vc_screenbuf in vc_do_resize()
In few older Samsung SoCs like s3c2410, s3c2412
and s3c2440, UART IP is having 2 interrupt lines.
However, in other SoCs like s3c6400, s5pv210,
exynos5433, and exynos4210 UART is having only 1
interrupt line. Due to this, "platform_get_irq(platdev, 1)"
call in the driver gives the following false-positive error:
"IRQ index 1 not found" on newer SoC's.
This patch adds the condition to check for Tx interrupt
only for the those SoC's which have 2 interrupt lines.
Tested-by: Alim Akhtar <alim.akhtar@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Tamseel Shams <m.shams@samsung.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200810030021.45348-1-m.shams@samsung.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
stm32_init_port() of the stm32-usart may trigger a warning in
platform_get_irq() when the device tree specifies no wakeup interrupt.
The wakeup interrupt is usually a board-specific GPIO and the driver
functions correctly in its absence. The mainline stm32mp151.dtsi does
not specify it, so all mainline device trees trigger an unnecessary
kernel warning. Use of platform_get_irq_optional() avoids this.
Fixes: 2c58e56096 ("serial: stm32: fix the get_irq error case")
Signed-off-by: Holger Assmann <h.assmann@pengutronix.de>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200813152757.32751-1-h.assmann@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
If probing of a pl011 gets deferred until after free_initmem(), an oops
ensues because pl011_console_match() is called which has been freed.
Fix by removing the __init attribute from the function and those it
calls.
Commit 10879ae5f1 ("serial: pl011: add console matching function")
introduced pl011_console_match() not just for early consoles but
regular preferred consoles, such as those added by acpi_parse_spcr().
Regular consoles may be registered after free_initmem() for various
reasons, one being deferred probing, another being dynamic enablement
of serial ports using a DeviceTree overlay.
Thus, pl011_console_match() must not be declared __init and the
functions it calls mustn't either.
Stack trace for posterity:
Unable to handle kernel paging request at virtual address 80c38b58
Internal error: Oops: 8000000d [#1] PREEMPT SMP ARM
PC is at pl011_console_match+0x0/0xfc
LR is at register_console+0x150/0x468
[<80187004>] (register_console)
[<805a8184>] (uart_add_one_port)
[<805b2b68>] (pl011_register_port)
[<805b3ce4>] (pl011_probe)
[<80569214>] (amba_probe)
[<805ca088>] (really_probe)
[<805ca2ec>] (driver_probe_device)
[<805ca5b0>] (__device_attach_driver)
[<805c8060>] (bus_for_each_drv)
[<805c9dfc>] (__device_attach)
[<805ca630>] (device_initial_probe)
[<805c90a8>] (bus_probe_device)
[<805c95a8>] (deferred_probe_work_func)
Fixes: 10879ae5f1 ("serial: pl011: add console matching function")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org # v4.10+
Cc: Aleksey Makarov <amakarov@marvell.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Christopher Covington <cov@codeaurora.org>
Link: https://lore.kernel.org/r/f827ff09da55b8c57d316a1b008a137677b58921.1597315557.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pl011_probe() calls pl011_setup_port() to reserve an amba_ports[] entry,
then calls pl011_register_port() to register the uart driver with the
tty layer.
If registration of the uart driver fails, the amba_ports[] entry is not
released. If this happens 14 times (value of UART_NR macro), then all
amba_ports[] entries will have been leaked and driver probing is no
longer possible. (To be fair, that can only happen if the DeviceTree
doesn't contain alias IDs since they cause the same entry to be used for
a given port.) Fix it.
Fixes: ef2889f7ff ("serial: pl011: Move uart_register_driver call to device")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org # v3.15+
Cc: Tushar Behera <tushar.behera@linaro.org>
Link: https://lore.kernel.org/r/138f8c15afb2f184d8102583f8301575566064a6.1597316167.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The following in 8250_exar.c line 589 is used to determine the number
of ports for each Exar board:
nr_ports = board->num_ports ? board->num_ports : pcidev->device & 0x0f;
If the number of ports a card has is not explicitly specified, it defaults
to the rightmost 4 bits of the PCI device ID. This is prone to error since
not all PCI device IDs contain a number which corresponds to the number of
ports that card provides.
This particular case involves COMMTECH_4222PCIE, COMMTECH_4224PCIE and
COMMTECH_4228PCIE cards with device IDs 0x0022, 0x0020 and 0x0021.
Currently the multiport cards receive 2, 0 and 1 port instead of 2, 4 and
8 ports respectively.
To fix this, each Commtech Fastcom PCIe card is given a struct where the
number of ports is explicitly specified. This ensures 'board->num_ports'
is used instead of the default 'pcidev->device & 0x0f'.
Fixes: d0aeaa83f0 ("serial: exar: split out the exar code from 8250_pci")
Signed-off-by: Valmer Huhn <valmer.huhn@concurrent-rt.com>
Tested-by: Valmer Huhn <valmer.huhn@concurrent-rt.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200813165255.GC345440@icarus.concurrent-rt.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The commit e42d6c3ec0 ("serial: qcom_geni_serial: Make kgdb work
even if UART isn't console") worked pretty well and I've been doing a
lot of debugging with it. However, recently I typed "dmesg" in kdb
and then held the space key down to scroll through the pagination. My
device hung. This was repeatable and I found that it was introduced
with the aforementioned commit.
It turns out that there are some strange boundary cases in geni where
in some weird situations it will signal RX_LAST but then will put 0 in
RX_LAST_BYTE. This means that the entire last FIFO entry is valid.
This weird corner case is handled in qcom_geni_serial_handle_rx()
where you can see that we only honor RX_LAST_BYTE if RX_LAST is set
_and_ RX_LAST_BYTE is non-zero. If either of these is not true we use
BYTES_PER_FIFO_WORD (4) for the size of the last FIFO word.
Let's fix kgdb. While at it, also use the proper #define for 4.
Fixes: e42d6c3ec0 ("serial: qcom_geni_serial: Make kgdb work even if UART isn't console")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Akash Asthana <akashast@codeaurora.org>
Link: https://lore.kernel.org/r/20200806221904.1.I4455ff86f0ef5281c2a0cd0a4712db614548a5ca@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Pull tty/serial updates from Greg KH:
"Here is the large set of TTY and Serial driver patches for 5.9-rc1.
Lots of bugfixes in here, thanks to syzbot fuzzing for serial and vt
and console code.
Other highlights include:
- much needed vt/vc code cleanup from Jiri Slaby
- 8250 driver fixes and additions
- various serial driver updates and feature enhancements
- locking cleanup for serial/console initializations
- other minor cleanups
All of these have been in linux-next with no reported issues"
* tag 'tty-5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (90 commits)
MAINTAINERS: enlist Greg formally for console stuff
vgacon: Fix for missing check in scrollback handling
Revert "serial: 8250: Let serial core initialise spin lock"
serial: 8250: Let serial core initialise spin lock
tty: keyboard, do not speculate on func_table index
serial: stm32: Add RS485 RTS GPIO control
serial: 8250_dw: Fix common clocks usage race condition
serial: 8250_dw: Pass the same rate to the clk round and set rate methods
serial: 8250_dw: Simplify the ref clock rate setting procedure
serial: 8250: Add 8250 port clock update method
tty: serial: imx: add imx earlycon driver
tty: serial: imx: enable imx serial console port as module
tty/synclink: remove leftover bits of non-PCI card support
tty: Use the preferred form for passing the size of a structure type
tty: Fix identation issues in struct serial_struct32
tty: Avoid the use of one-element arrays
serial: msm_serial: add sparse context annotation
serial: pmac_zilog: add sparse context annotation
newport_con: vc_color is now in state
serial: imx: use hrtimers for rs485 delays
...
Pull sched/fifo updates from Ingo Molnar:
"This adds the sched_set_fifo*() encapsulation APIs to remove static
priority level knowledge from non-scheduler code.
The three APIs for non-scheduler code to set SCHED_FIFO are:
- sched_set_fifo()
- sched_set_fifo_low()
- sched_set_normal()
These are two FIFO priority levels: default (high), and a 'low'
priority level, plus sched_set_normal() to set the policy back to
non-SCHED_FIFO.
Since the changes affect a lot of non-scheduler code, we kept this in
a separate tree"
* tag 'sched-fifo-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
sched,tracing: Convert to sched_set_fifo()
sched: Remove sched_set_*() return value
sched: Remove sched_setscheduler*() EXPORTs
sched,psi: Convert to sched_set_fifo_low()
sched,rcutorture: Convert to sched_set_fifo_low()
sched,rcuperf: Convert to sched_set_fifo_low()
sched,locktorture: Convert to sched_set_fifo()
sched,irq: Convert to sched_set_fifo()
sched,watchdog: Convert to sched_set_fifo()
sched,serial: Convert to sched_set_fifo()
sched,powerclamp: Convert to sched_set_fifo()
sched,ion: Convert to sched_set_normal()
sched,powercap: Convert to sched_set_fifo*()
sched,spi: Convert to sched_set_fifo*()
sched,mmc: Convert to sched_set_fifo*()
sched,ivtv: Convert to sched_set_fifo*()
sched,drm/scheduler: Convert to sched_set_fifo*()
sched,msm: Convert to sched_set_fifo*()
sched,psci: Convert to sched_set_fifo*()
sched,drbd: Convert to sched_set_fifo*()
...
Pull printk updates from Petr Mladek:
- Herbert Xu made printk header file self-contained.
- Andy Shevchenko and Sergey Senozhatsky cleaned up console->setup()
error handling.
- Andy Shevchenko did some cleanups (e.g. sparse warning) in vsprintf
code.
- Minor documentation updates.
* tag 'printk-for-5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
lib/vsprintf: Force type of flags value for gfp_t
lib/vsprintf: Replace custom spec to print decimals with generic one
lib/vsprintf: Replace hidden BUILD_BUG_ON() with static_assert()
printk: Make linux/printk.h self-contained
doc:kmsg: explicitly state the return value in case of SEEK_CUR
Replace HTTP links with HTTPS ones: vsprintf
hvc: unify console setup naming
console: Fix trivia typo 'change' -> 'chance'
console: Propagate error code from console ->setup()
tty: hvc: Return proper error code from console ->setup() hook
serial: sunzilog: Return proper error code from console ->setup() hook
serial: sunsab: Return proper error code from console ->setup() hook
mips: Return proper error code from console ->setup() hook
Pull ARM SoC driver updates from Arnd Bergmann:
"A couple of subsystems have their own subsystem maintainers but choose
to have the code merged through the soc tree as upstream, as the code
tends to be used across multiple SoCs or has SoC specific drivers
itself:
- memory controllers:
Krzysztof Kozlowski takes ownership of the drivers/memory subsystem
and its drivers, starting out with a set of cleanup patches.
A larger driver for the Tegra memory controller that was
accidentally missed for v5.8 is now added.
- reset controllers:
Only minor updates to drivers/reset this time
- firmware:
The "turris mox" firmware driver gains support for signed firmware
blobs The tegra firmware driver gets extended to export some debug
information Various updates to i.MX firmware drivers, mostly
cosmetic
- ARM SCMI/SCPI:
A new mechanism for platform notifications is added, among a number
of minor changes.
- optee:
Probing of the TEE bus is rewritten to better support detection of
devices that depend on the tee-supplicant user space. A new
firmware based trusted platform module (fTPM) driver is added based
on OP-TEE
- SoC attributes:
A new driver is added to provide a generic soc_device for
identifying a machine through the SMCCC ARCH_SOC_ID firmware
interface rather than by probing SoC family specific registers.
The series also contains some cleanups to the common soc_device
code.
There are also a number of updates to SoC specific drivers, the main
ones are:
- Mediatek cmdq driver gains a few in-kernel interfaces
- Minor updates to Qualcomm RPMh, socinfo, rpm drivers, mostly adding
support for additional SoC variants
- The Qualcomm GENI core code gains interconnect path voting and
performance level support, and integrating this into a number of
device drivers.
- A new driver for Samsung Exynos5800 voltage coupler for
- Renesas RZ/G2H (R8A774E1) SoC support gets added to a couple of SoC
specific device drivers
- Updates to the TI K3 Ring Accelerator driver"
* tag 'arm-drivers-5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: (164 commits)
soc: qcom: geni: Fix unused label warning
soc: qcom: smd-rpm: Fix kerneldoc
memory: jz4780_nemc: Only request IO memory the driver will use
soc: qcom: pdr: Reorder the PD state indication ack
MAINTAINERS: Add Git repository for memory controller drivers
memory: brcmstb_dpfe: Fix language typo
memory: samsung: exynos5422-dmc: Correct white space issues
memory: samsung: exynos-srom: Correct alignment
memory: pl172: Enclose macro argument usage in parenthesis
memory: of: Correct kerneldoc
memory: omap-gpmc: Fix language typo
memory: omap-gpmc: Correct white space issues
memory: omap-gpmc: Use 'unsigned int' for consistency
memory: omap-gpmc: Enclose macro argument usage in parenthesis
memory: omap-gpmc: Correct kerneldoc
memory: mvebu-devbus: Align with open parenthesis
memory: mvebu-devbus: Add missing braces to all arms of if statement
memory: bt1-l2-ctl: Add blank lines after declarations
soc: TI knav_qmss: make symbol 'knav_acc_range_ops' static
firmware: ti_sci: Replace HTTP links with HTTPS ones
...
The race condition may happen if the UART reference clock is shared with
some other device (on Baikal-T1 SoC it's another DW UART port). In this
case if that device changes the clock rate while serial console is using
it the DW 8250 UART port might not only end up with an invalid uartclk
value saved, but may also experience a distorted output data since
baud-clock could have been changed. In order to fix this lets at least
try to adjust the 8250 port setting like UART clock rate in case if the
reference clock rate change is discovered. The driver will call the new
method to update 8250 UART port clock rate settings. It's done by means of
the clock event notifier registered at the port startup and unregistered
in the shutdown callback method.
Note 1. In order to avoid deadlocks we had to execute the UART port update
method in a dedicated deferred work. This is due to (in my opinion
redundant) the clock update implemented in the dw8250_set_termios()
method.
Note 2. Before the ref clock is manually changed by the custom
set_termios() function we swap the port uartclk value with new rate
adjusted to be suitable for the requested baud. It is necessary in
order to effectively disable a functionality of the ref clock events
handler for the current UART port, since uartclk update will be done
a bit further in the generic serial8250_do_set_termios() function.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200723003357.26897-5-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
