Revert "serial: 8250: Switch to nbcon console"

This reverts commit b63e6f60eab45b16a1bf734fef9035a4c4187cd5.

kernel test robot has found problems with this commit so revert it for
now.

Link: https

Revert "serial: 8250: Switch to nbcon console"

This reverts commit b63e6f60eab45b16a1bf734fef9035a4c4187cd5.

kernel test robot has found problems with this commit so revert it for
now.

Link: https://lore.kernel.org/r/[email protected]
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-lkp/[email protected]
Cc: John Ogness <[email protected]>
Cc: Petr Mladek <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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serial: 8250: Switch to nbcon console

Implement the necessary callbacks to switch the 8250 console driver
to perform as an nbcon console.

Add implementations for the nbcon console callbacks:

->w

serial: 8250: Switch to nbcon console

Implement the necessary callbacks to switch the 8250 console driver
to perform as an nbcon console.

Add implementations for the nbcon console callbacks:

->write_atomic()
->write_thread()
->device_lock()
->device_unlock()

and add CON_NBCON to the initial @flags.

All register access in the callbacks are within unsafe sections.
The ->write_atomic() and ->write_thread() callbacks allow safe
handover/takeover per byte and add a preceding newline if they
take over from another context mid-line.

For the ->write_atomic() callback, a new irq_work is used to defer
modem control since it may be called from a context that does not
allow waking up tasks.

Note: A new __serial8250_clear_IER() is introduced for direct
clearing of UART_IER. This will allow to restore the lockdep
check to serial8250_clear_IER() in a follow-up commit.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Tested-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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serial: 8250: Provide flag for IER toggling for RS485

For RS485 mode, if SER_RS485_RX_DURING_TX is not available, the
console ->write() callback needs to enable/disable Tx. It does
this by calling t

serial: 8250: Provide flag for IER toggling for RS485

For RS485 mode, if SER_RS485_RX_DURING_TX is not available, the
console ->write() callback needs to enable/disable Tx. It does
this by calling the ->rs485_start_tx() and ->rs485_stop_tx()
callbacks. However, some of these callbacks also disable/enable
interrupts and makes power management calls. This causes 2
problems for console writing:

1. A console write can occur in contexts that are illegal for
pm_runtime_*(). It is not even necessary for console writing
to use pm_runtime_*() because a console already does this in
serial8250_console_setup() and serial8250_console_exit().

2. The console ->write() callback already handles
disabling/enabling the interrupts by properly restoring the
previous IER value.

Add an argument @toggle_ier to the ->rs485_start_tx() and
->rs485_stop_tx() callbacks to specify if they may disable/enable
receive interrupts while using pm_runtime_*(). Console writing
will not allow the toggling.

For all call sites other than console writing there is no
functional change.

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

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serial: remove quot_frac from serial8250_do_set_divisor()

quot_frac is unused in serial8250_do_set_divisor() since commit
b2b4b8ed3c06 (serial: 8250_exar: Move custom divisor support out from
8250_p

serial: remove quot_frac from serial8250_do_set_divisor()

quot_frac is unused in serial8250_do_set_divisor() since commit
b2b4b8ed3c06 (serial: 8250_exar: Move custom divisor support out from
8250_port). So no point to pass it.

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

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serial: 8250: Move hp300_setup_serial_console() to <linux/serial_8250.h>

If CONFIG_SERIAL_8250_HP300=y and CONFIG_SERIAL_8250_CONSOLE=y (e.g.
m68k/allyesconfig):

drivers/tty/serial/8250/8250_hp

serial: 8250: Move hp300_setup_serial_console() to <linux/serial_8250.h>

If CONFIG_SERIAL_8250_HP300=y and CONFIG_SERIAL_8250_CONSOLE=y (e.g.
m68k/allyesconfig):

drivers/tty/serial/8250/8250_hp300.c:91:12: error: no previous prototype for ‘hp300_setup_serial_console’ [-Werror=missing-prototypes]
91 | int __init hp300_setup_serial_console(void)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~

Fix this by moving the existing prototype in arch/m68k/hp300/config.c to
<linux/serial_8250.h>, so it is visible to both caller and implementor.
While at it, provide a dummy in case CONFIG_SERIAL_8250_CONSOLE is not
enabled, to reduce #ifdef clutter in the caller.

Exposed by commit 0fcb70851fbfea17 ("Makefile.extrawarn: turn on
missing-prototypes globally").

Signed-off-by: Geert Uytterhoeven <[email protected]>
Link: https://lore.kernel.org/r/c17469f8e47b2ef49234a85a7a14882ddf374e41.1704892597.git.geert@linux-m68k.org
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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Revert "8250: add support for ASIX devices with a FIFO bug"

This reverts commit eb26dfe8aa7eeb5a5aa0b7574550125f8aa4c3b3.

Commit eb26dfe8aa7e ("8250: add support for ASIX devices with a FIFO
bug")

Revert "8250: add support for ASIX devices with a FIFO bug"

This reverts commit eb26dfe8aa7eeb5a5aa0b7574550125f8aa4c3b3.

Commit eb26dfe8aa7e ("8250: add support for ASIX devices with a FIFO
bug") merged on Jul 13, 2012 adds a quirk for PCI_VENDOR_ID_ASIX
(0x9710). But that ID is the same as PCI_VENDOR_ID_NETMOS defined in
1f8b061050c7 ("[PATCH] Netmos parallel/serial/combo support") merged
on Mar 28, 2005. In pci_serial_quirks array, the NetMos entry always
takes precedence over the ASIX entry even since it was initially
merged, code in that commit is always unreachable.

In my tests, adding the FIFO workaround to pci_netmos_init() makes no
difference, and the vendor driver also does not have such workaround.
Given that the code was never used for over a decade, it's safe to
revert it.

Also, the real PCI_VENDOR_ID_ASIX should be 0x125b, which is used on
their newer AX99100 PCIe serial controllers released on 2016. The FIFO
workaround should not be intended for these newer controllers, and it
was never implemented in vendor driver.

Fixes: eb26dfe8aa7e ("8250: add support for ASIX devices with a FIFO bug")
Cc: stable <[email protected]>
Signed-off-by: Jiaqing Zhao <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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serial: 8250: RT288x/Au1xxx code away from core

A non-trivial amount of RT288x/Au1xxx code is encapsulated into
ifdeffery in 8250_port / 8250_early and some if UPIO_AU blocks.
Create a separate file

serial: 8250: RT288x/Au1xxx code away from core

A non-trivial amount of RT288x/Au1xxx code is encapsulated into
ifdeffery in 8250_port / 8250_early and some if UPIO_AU blocks.
Create a separate file from them.

Also handle errors properly in the cases where RT288x/Au1xxx code is
not configured.

It seems that 0x1000 mapsize is likely overkill but I've kept it the
same as previously (the value was shrunk to that value in commit
b2b13cdfd05e ("SERIAL 8250: Fixes for Alchemy UARTs.")). Seemingly, the
driver only needs to access register at 0x28 for the divisor latch.

The Kconfig side is a bit tricky. As SERIAL_8250_RT288X is bool it can
only be =y. It is possible to have SERIAL_8250=m + SERIAL_8250_RT288X=y
which required altering when 8250/ is included or the rt288x would not
be built.

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: 8250: Add dl_read/write, bugs and mapsize into plat_serial8250_port

Add mapsize, bugs, and divisor latch read/write functions
(->dl_read/write()) into plat_serial8250_port to carry the setup

serial: 8250: Add dl_read/write, bugs and mapsize into plat_serial8250_port

Add mapsize, bugs, and divisor latch read/write functions
(->dl_read/write()) into plat_serial8250_port to carry the setup
necessary for RT288x/Au1xxx devices over to uart port.

Document the added members with kerneldoc style but do not enable
kerneldoc yet as there are many fields which remain undocumented.

While at it, convert .bugs in struct uart_8250_port to u16 to match it
with the type used in struct plat_serial8250_port.

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: 8250: Document uart_8250_port's ->dl_read/write()

Add documentation for the struct uart_8250_port divisor latch function
pointers. Documentation is in kernel doc format but don't enable kern

serial: 8250: Document uart_8250_port's ->dl_read/write()

Add documentation for the struct uart_8250_port divisor latch function
pointers. Documentation is in kernel doc format but don't enable kernel
doc yet as many other fields remain undocumented.

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: 8250: Change dl_read/write to handle value as u32

Divisor latch read/write functions currently handle the value is int.
As the value is related to HW context, u32 makes much more sense than

serial: 8250: Change dl_read/write to handle value as u32

Divisor latch read/write functions currently handle the value is int.
As the value is related to HW context, u32 makes much more sense than a
signed type.

While at it, name the parameters in the callback signature.

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: Remove extern from func prototypes in headers

Remove unnecessary externs from function prototypes in serial_8250.h
and serial_core.h.

Suggested-by: Jiri Slaby <[email protected]>
Signed-

serial: Remove extern from func prototypes in headers

Remove unnecessary externs from function prototypes in serial_8250.h
and serial_core.h.

Suggested-by: Jiri Slaby <[email protected]>
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: 8250: Reorder fields in 'struct plat_serial8250_port'

Group some variables based on their sizes to reduce hole and avoid padding.
On x86_64, this shrinks the size of 'struct plat_serial8250_

serial: 8250: Reorder fields in 'struct plat_serial8250_port'

Group some variables based on their sizes to reduce hole and avoid padding.
On x86_64, this shrinks the size of 'struct plat_serial8250_port'
from 144 to 128 bytes.

It saves a few bytes of memory.

Signed-off-by: Christophe JAILLET <[email protected]>
Link: https://lore.kernel.org/r/f3cb1efe1454e0615840fd331ee335bc441589a9.1676665358.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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serial: 8250: Toggle IER bits on only after irq has been set up

Invoking TIOCVHANGUP on 8250_mid port on Ice Lake-D and then reopening
the port triggers these faults during serial8250_do_startup():

serial: 8250: Toggle IER bits on only after irq has been set up

Invoking TIOCVHANGUP on 8250_mid port on Ice Lake-D and then reopening
the port triggers these faults during serial8250_do_startup():

DMAR: DRHD: handling fault status reg 3
DMAR: [DMA Write NO_PASID] Request device [00:1a.0] fault addr 0x0 [fault reason 0x05] PTE Write access is not set

If the IRQ hasn't been set up yet, the UART will have zeroes in its MSI
address/data registers. Disabling the IRQ at the interrupt controller
won't stop the UART from performing a DMA write to the address programmed
in its MSI address register (zero) when it wants to signal an interrupt.

The UARTs (in Ice Lake-D) implement PCI 2.1 style MSI without masking
capability, so there is no way to mask the interrupt at the source PCI
function level, except disabling the MSI capability entirely, but that
would cause it to fall back to INTx# assertion, and the PCI specification
prohibits disabling the MSI capability as a way to mask a function's
interrupt service request.

The MSI address register is zeroed by the hangup as the irq is freed.
The interrupt is signalled during serial8250_do_startup() performing a
THRE test that temporarily toggles THRI in IER. The THRE test currently
occurs before UART's irq (and MSI address) is properly set up.

Refactor serial8250_do_startup() such that irq is set up before the
THRE test. The current irq setup code is intermixed with the timer
setup code. As THRE test must be performed prior to the timer setup,
extract it into own function and call it only after the THRE test.

The ->setup_timer() needs to be part of the struct uart_8250_ops in
order to not create circular dependency between 8250 and 8250_base
modules.

Fixes: 40b36daad0ac ("[PATCH] 8250 UART backup timer")
Reported-by: Lennert Buytenhek <[email protected]>
Tested-by: Lennert Buytenhek <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
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: Make ->set_termios() old ktermios const

There should be no reason to adjust old ktermios which is going to get
discarded anyway.

Reviewed-by: Andy Shevchenko <[email protected]>
Sig

serial: Make ->set_termios() old ktermios const

There should be no reason to adjust old ktermios which is going to get
discarded anyway.

Reviewed-by: Andy Shevchenko <[email protected]>
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: 8250: create lsr_save_mask

Allow drivers to alter LSR save mask.

Reviewed-by: Andy Shevchenko <[email protected]>
Signed-off-by: Ilpo Järvinen <[email protected]

serial: 8250: create lsr_save_mask

Allow drivers to alter LSR save mask.

Reviewed-by: Andy Shevchenko <[email protected]>
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: 8250: make saved LSR larger

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 chain

serial: 8250: make saved LSR larger

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

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Revert "serial: 8250: Handle UART without interrupt on TEMT using em485"

This partially reverts commit f6f586102add. The code added by
that commit containted math overflow for 32-bit archs. In
addit

Revert "serial: 8250: Handle UART without interrupt on TEMT using em485"

This partially reverts commit f6f586102add. The code added by
that commit containted math overflow for 32-bit archs. In
addition, the approach used in it is unnecessarily complicated
requiring a dedicated timer just for notemt. A simpler approach
for providing UART_CAP_NOTEMT already exists (patches 1-2):
https://lore.kernel.org/linux-serial/[email protected]/T/#u
Thus, simply revert the UART_CAP_NOTEMT change for now.

There were two driver changes within the patch series adding
UART_CAP_NOTEMT taking advantage of the newly added flag.
This does not revert the driver changes and therefore also
UART_CAP_NOTEMT define has to remain. UART_CAP_NOTEMT remains
no-op until support is again added.

Fixes: f6f586102add ("serial: 8250: Handle UART without interrupt on TEMT using em485")
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: 8250: Handle UART without interrupt on TEMT using em485

Introduce the UART_CAP_NOTEMT capability. The capability indicates that
the UART doesn't have an interrupt available on TEMT.

In the

serial: 8250: Handle UART without interrupt on TEMT using em485

Introduce the UART_CAP_NOTEMT capability. The capability indicates that
the UART doesn't have an interrupt available on TEMT.

In the case where the device does not support it, we calculate the
maximum time it could take for the transmitter to empty the
shift register. When we get in the situation where we get the
THRE interrupt, we check if the TEMT bit is set. If it's not, we start
the a timer and recall __stop_tx() after the delay.

The transmit sequence is a bit modified when the capability is set. The
new timer is used between the last interrupt(THRE) and a potential
stop_tx timer.

Signed-off-by: Giulio Benetti <[email protected]>
[moved to use added UART_CAP_TEMT]
Signed-off-by: Heiko Stuebner <[email protected]>
[moved to use added UART_CAP_NOTEMT, improve timeout]
Signed-off-by: Eric Tremblay <[email protected]>
[rebased to v5.17, making use of tty_get_frame_size]
Signed-off-by: Uwe Kleine-König <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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

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

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

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 <[email protected]>
Cc: Ulrich Teichert <[email protected]>
Cc: Linus Torvalds <[email protected]>
Signed-off-by: Lukas Wunner <[email protected]>
Link: https://lore.kernel.org/r/b83d069cb516549b8a5420e097bb6bdd806f36fc.1640695609.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty/serial: make port of serial8250_register_8250_port const

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 seria

tty/serial: make port of serial8250_register_8250_port const

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

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

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

drivers/tty/serial/8250/8250_port.c:349:14: warning: no previous prototype for ‘au

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

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

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serial: 8250: Add 8250 port clock update method

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
happ

serial: 8250: Add 8250 port clock update method

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 <[email protected]>

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

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

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 a

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

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

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serial: 8250: Generalize rs485 software emulation

Commit e490c9144cfa ("tty: Add software emulated RS485 support for 8250")
introduced support to use RTS as an rs485 Transmit Enable signal.
So far t

serial: 8250: Generalize rs485 software emulation

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 <[email protected]>
Cc: Matwey V. Kornilov <[email protected]>
Link: https://lore.kernel.org/r/5ac0464ae4414708e723a1e0d52b0c1b2bd41b9b.1582895077.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty/serial: Migrate 8250_fsl to use has_sysrq

The SUPPORT_SYSRQ ifdeffery is not nice as:
- May create misunderstanding about sizeof(struct uart_port) between
different objects
- Prevents moving f

tty/serial: Migrate 8250_fsl to use has_sysrq

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 <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: [email protected]
Signed-off-by: Dmitry Safonov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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