On the embedded platform, certain critical data, such as IMU data, is
transmitted through UART. The tty_flip_buffer_push() interface in the TTY
layer uses system_dfl_wq to handle the flipping of the TTY buffer.
Although the unbound workqueue can create new threads on demand and wake
up the kworker thread on an idle CPU, it may be preempted by real-time
tasks or other high-prio tasks.
flush_to_ldisc() needs to wake up the relevant data handle thread. When
executing __wake_up_common_lock(), it calls spin_lock_irqsave(), which
does not disable preemption but disables migration in RT-Linux. This
prevents the kworker thread from being migrated to other cores by CPU's
balancing logic, resulting in long delays. The call trace is as follows:
__wake_up_common_lock
__wake_up
ep_poll_callback
__wake_up_common
__wake_up_common_lock
__wake_up
n_tty_receive_buf_common
n_tty_receive_buf2
tty_ldisc_receive_buf
tty_port_default_receive_buf
flush_to_ldisc
In our system, the processing interval for each frame of IMU data
transmitted via UART can experience significant jitter due to this issue.
Instead of the expected 10 to 15 ms frame processing interval, we see
spikes up to 30 to 35 ms. Moreover, in just one or two hours, there can
be 2 to 3 occurrences of such high jitter, which is quite frequent. This
jitter exceeds the software's tolerable limit of 20 ms.
Introduce flip_wq in tty_port which can be set by tty_port_link_wq() or as
default linked to default workqueue allocated when tty_register_driver().
The default workqueue is allocated with flag WQ_SYSFS, so that cpumask and
nice can be set dynamically. The execution timing of tty_port_link_wq() is
not clearly restricted. The newly added function tty_port_link_driver_wq()
checks whether the flip_wq of the tty_port has already been assigned when
linking the default tty_driver's workqueue to the port. After the user has
set a custom workqueue for a certain tty_port using tty_port_link_wq(), the
system will only use this custom workqueue, even if tty_driver does not
have %TTY_DRIVER_NO_WORKQUEUE flag. When tty_port register device, flip_wq
link operation is done by tty_port_link_driver_wq(), but for in-memory
devices the link operation cannot cover all the cases. Although
tty_port_install() is dedicated for in-memory devices lik PTY to link port
allocated on demand, the logic of tty_port_install() is so simple that
people may not call it, vc_cons[0].d->port is one such case. We check the
buf.flip_wq when flip TTY buffer, if buf.flip_wq of TTY port is NULL, use
system_dfl_wq as a backup.
To avoid naming conflict of the default tty_driver's workqueue, using
'"%s-%s", driver->name, driver->driver_name' as the workqueue name. In
cases where driver_name is not specified and therefore is NULL, the
workqueue is not created. Drivers that do not define driver_name are
potentially in-memory devices like vty, which generally do not require
special workqueue settings. Even with the combination of name and
driver_name, the workqueue names can still be duplicated, as many tty
serial drivers use "ttyS" as dev_name and "serial" as driver_name. I
modified the conflicting driver_name of these drivers by appending a
suffix of _xx based on the corresponding .c file. If this modification is
not made, it could not only lead to duplicate workqueue names but also
result in duplicate entries for the /proc/tty/driver/<driver_name> nodes.
Introduce %TTY_DRIVER_NO_WORKQUEUE flag meaning not to create the
default single tty_driver workqueue. Two reasons why need to introduce the
%TTY_DRIVER_NO_WORKQUEUE flag:
1. If the WQ_SYSFS parameter is enabled, workqueue_sysfs_register() will
fail when trying to create a workqueue with the same name. The pty is an
example of this; if both CONFIG_LEGACY_PTYS and CONFIG_UNIX98_PTYS are
enabled, the call to tty_register_driver() in unix98_pty_init() will fail.
2. Different TTY ports may be used for different tasks, which may require
separate core binding control via workqueues. In this case, the workqueue
created by default in the TTY driver is unnecessary. Enabling this flag
prevents the creation of this redundant workqueue.
After applying this patch, we can set the related UART TTY flip buffer
workqueue by sysfs. We set the cpumask to CPU cores associated with the
IMU tasks, and set the nice to -20. Testing has shown significant
improvement in the previously described issue, with almost no stuttering
occurring anymore.
Tested-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Xin Zhao <jackzxcui1989@163.com>
Link: https://patch.msgid.link/20260213085039.3274704-1-jackzxcui1989@163.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
After commit 84a9582fd2 ("serial: core: Start managing serial controllers
to enable runtime PM") serial drivers need to provide a device in
struct uart_port.dev otherwise an oops happens. To fix this issue
for ip22zilog driver switch driver to a platform driver and setup
the serial device in sgi-ip22 code.
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Link: https://lore.kernel.org/r/20250725134018.136113-1-tsbogend@alpha.franken.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Switch from struct circ_buf to proper kfifo. kfifo provides much better
API, esp. when wrap-around of the buffer needs to be taken into account.
Look at pl011_dma_tx_refill() or cpm_uart_tx_pump() changes for example.
Kfifo API can also fill in scatter-gather DMA structures, so it easier
for that use case too. Look at lpuart_dma_tx() for example. Note that
not all drivers can be converted to that (like atmel_serial), they
handle DMA specially.
Note that usb-serial uses kfifo for TX for ages.
omap needed a bit more care as it needs to put a char into FIFO to start
the DMA transfer when OMAP_DMA_TX_KICK is set. In that case, we have to
do kfifo_dma_out_prepare twice: once to find out the tx_size (to find
out if it is worths to do DMA at all -- size >= 4), the second time for
the actual transfer.
All traces of circ_buf are removed from serial_core.h (and its struct
uart_state).
Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Al Cooper <alcooperx@gmail.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: Kumaravel Thiagarajan <kumaravel.thiagarajan@microchip.com>
Cc: Tharun Kumar P <tharunkumar.pasumarthi@microchip.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Vineet Gupta <vgupta@kernel.org>
Cc: Richard Genoud <richard.genoud@gmail.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Cc: Alexander Shiyan <shc_work@mail.ru>
Cc: Baruch Siach <baruch@tkos.co.il>
Cc: Maciej W. Rozycki <macro@orcam.me.uk>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Neil Armstrong <neil.armstrong@linaro.org>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: Taichi Sugaya <sugaya.taichi@socionext.com>
Cc: Takao Orito <orito.takao@socionext.com>
Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>
Cc: Pali Rohár <pali@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Alim Akhtar <alim.akhtar@samsung.com>
Cc: Laxman Dewangan <ldewangan@nvidia.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: Orson Zhai <orsonzhai@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Hammer Hsieh <hammerh0314@gmail.com>
Cc: Peter Korsgaard <jacmet@sunsite.dk>
Cc: Timur Tabi <timur@kernel.org>
Cc: Michal Simek <michal.simek@amd.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20240405060826.2521-13-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.
To avoid adding this functionality to all UART drivers, wrap the
spin_[un]lock*() invocations for uart_port::lock into helper functions
which just contain the spin_[un]lock*() invocations for now. In a
subsequent step these helpers will gain the console synchronization
mechanisms.
Converted with coccinelle. No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Link: https://lore.kernel.org/r/20230914183831.587273-31-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
There should be no reason to adjust old ktermios which is going to get
discarded anyway.
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220816115739.10928-7-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Currently, uart_console_write->putchar's second parameter (the
character) is of type int. It makes little sense, provided uart_console_write()
accepts the input string as "const char *s" and passes its content -- the
characters -- to putchar(). So switch the character's type to unsigned
char.
We don't use char as that is signed on some platforms. That would cause
troubles for drivers which (implicitly) cast the char to u16 when
writing to the device. Sign extension would happen in that case and the
value written would be completely different to the provided char. DZ is
an example of such a driver -- on MIPS, it uses u16 for dz_out in
dz_console_putchar().
Note we do the char -> uchar conversion implicitly in
uart_console_write(). Provided we do not change size of the data type,
sign extension does not happen there, so the problem is void.
This makes the types consistent and unified with the rest of the uart
layer, which uses unsigned char in most places already. One exception is
xmit_buf, but that is going to be converted later.
Cc: Paul Cercueil <paul@crapouillou.net>
Cc: Tobias Klauser <tklauser@distanz.ch>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Vineet Gupta <vgupta@kernel.org>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: bcm-kernel-feedback-list@broadcom.com
Cc: Alexander Shiyan <shc_work@mail.ru>
Cc: Baruch Siach <baruch@tkos.co.il>
Cc: "Maciej W. Rozycki" <macro@orcam.me.uk>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: Karol Gugala <kgugala@antmicro.com>
Cc: Mateusz Holenko <mholenko@antmicro.com>
Cc: Vladimir Zapolskiy <vz@mleia.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: Taichi Sugaya <sugaya.taichi@socionext.com>
Cc: Takao Orito <orito.takao@socionext.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: "Andreas Färber" <afaerber@suse.de>
Cc: Manivannan Sadhasivam <mani@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Cc: Orson Zhai <orsonzhai@gmail.com>
Cc: Baolin Wang <baolin.wang7@gmail.com>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Peter Korsgaard <peter@korsgaard.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Acked-by: Richard Genoud <richard.genoud@gmail.com> [atmel_serial]
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Neil Armstrong <narmstrong@baylibre.com> # meson_serial
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220303080831.21783-1-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Include the more general linux/io.h instead of asm/io.h
as checkpatch suggests.
Signed-off-by: Zihao Tang <tangzihao1@hisilicon.com>
Signed-off-by: Jay Fang <f.fangjian@huawei.com>
Link: https://lore.kernel.org/r/1620874904-39285-5-git-send-email-f.fangjian@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.
Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20191213000657.931618-21-dima@arista.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.
Update the drivers/tty files files with the correct SPDX license
identifier based on the license text in the file itself. The SPDX
identifier is a legally binding shorthand, which can be used instead of
the full boiler plate text.
This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: David Sterba <dsterba@suse.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Eric Anholt <eric@anholt.net>
Cc: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ray Jui <rjui@broadcom.com>
Cc: Scott Branden <sbranden@broadcom.com>
Cc: bcm-kernel-feedback-list@broadcom.com
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Joachim Eastwood <manabian@gmail.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Tobias Klauser <tklauser@distanz.ch>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Richard Genoud <richard.genoud@gmail.com>
Cc: Alexander Shiyan <shc_work@mail.ru>
Cc: Baruch Siach <baruch@tkos.co.il>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>
Cc: "Uwe Kleine-König" <kernel@pengutronix.de>
Cc: Pat Gefre <pfg@sgi.com>
Cc: "Guilherme G. Piccoli" <gpiccoli@linux.vnet.ibm.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Vladimir Zapolskiy <vz@mleia.com>
Cc: Sylvain Lemieux <slemieux.tyco@gmail.com>
Cc: Carlo Caione <carlo@caione.org>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Andy Gross <andy.gross@linaro.org>
Cc: David Brown <david.brown@linaro.org>
Cc: "Andreas Färber" <afaerber@suse.de>
Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Laxman Dewangan <ldewangan@nvidia.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Patrice Chotard <patrice.chotard@st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Peter Korsgaard <jacmet@sunsite.dk>
Cc: Timur Tabi <timur@tabi.org>
Cc: Tony Prisk <linux@prisktech.co.nz>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: "Sören Brinkmann" <soren.brinkmann@xilinx.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Jiri Slaby <jslaby@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Use container_of instead of casting first structure member.
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit 717f3bbab3,
'serial_core: Fix conditional start_tx on ring buffer not empty'
exposes an incorrect assumption in several drivers' start_tx methods;
the tx ring buffer can, in fact, be empty when restarting tx while
performing flow control.
Affected drivers:
sunsab.c
ip22zilog.c
pmac_zilog.c
sunzilog.c
m32r_sio.c
imx.c
Other in-tree serial drivers either are not affected or already
test for empty tx ring buffer before transmitting.
Test for empty tx ring buffer in start_tx() method, after transmitting
x_char (if applicable).
Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Seth Bollinger <sethb@digi.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org> # 3.15
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
If IGNBRK is set without either BRKINT or PARMRK set, some uart
drivers send a 0x00 byte for BREAK without the TTYBREAK flag to the
line discipline, when it should send either nothing or the TTYBREAK flag
set. This happens because the read_status_mask masks out the BI
condition, which uart_insert_char() then interprets as a normal 0x00 byte.
SUS v3 is clear regarding the meaning of IGNBRK; Section 11.2.2, General
Terminal Interface - Input Modes, states:
"If IGNBRK is set, a break condition detected on input shall be ignored;
that is, not put on the input queue and therefore not read by any
process."
Fix read_status_mask to include the BI bit if IGNBRK is set; the
lsr status retains the BI bit if a BREAK is recv'd, which is
subsequently ignored in uart_insert_char() when masked with the
ignore_status_mask.
Affected drivers:
8250 - all
serial_txx9
mfd
amba-pl010
amba-pl011
atmel_serial
bfin_uart
dz
ip22zilog
max310x
mxs-auart
netx-serial
pnx8xxx_uart
pxa
sb1250-duart
sccnxp
serial_ks8695
sirfsoc_uart
st-asc
vr41xx_siu
zs
sunzilog
fsl_lpuart
sunsab
ucc_uart
bcm63xx_uart
sunsu
efm32-uart
pmac_zilog
mpsc
msm_serial
m32r_sio
Unaffected drivers:
omap-serial
rp2
sa1100
imx
icom
Annotated for fixes:
altera_uart
mcf
Drivers without break detection:
21285
xilinx-uartps
altera_jtaguart
apbuart
arc-uart
clps711x
max3100
uartlite
msm_serial_hs
nwpserial
lantiq
vt8500_serial
Unknown:
samsung
mpc52xx_uart
bfin_sport_uart
cpm_uart/core
Fixes: Bugzilla #71651, '8250_core.c incorrectly handles IGNBRK flag'
Reported-by: Ivan <athlon_@mail.ru>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
These aren't necessary after switch and while blocks.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This one was omitted by the "TTY: switch tty_flip_buffer_push" patch
because I did not compile-test mips driver. Now I do.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The serial drivers are really just tty drivers, so move them to
drivers/tty/ to make things a bit neater overall.
This is part of the tty/serial driver movement proceedure as proposed by
Arnd Bergmann and approved by everyone involved a number of months ago.
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Rogier Wolff <R.E.Wolff@bitwizard.nl>
Cc: Michael H. Warfield <mhw@wittsend.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
