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>
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 <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200723003357.26897-2-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Sealevel XR17V35X based devices are inoperable on kernel versions
4.11 and above due to a change in the GPIO preconfiguration introduced in
commit
7dea8165f1. This patch fixes this by preconfiguring the GPIO on Sealevel
cards to the value (0x00) used prior to commit 7dea8165f1
With GPIOs preconfigured as per commit 7dea8165f1 all ports on
Sealevel XR17V35X based devices become stuck in high impedance
mode, regardless of dip-switch or software configuration. This
causes the device to become effectively unusable. This patch (in
various forms) has been distributed to our customers and no issues
related to it have been reported.
Fixes: 7dea8165f1 ("serial: exar: Preconfigure xr17v35x MPIOs as output")
Signed-off-by: Matthew Howell <matthew.howell@sealevel.com>
Link: https://lore.kernel.org/r/alpine.DEB.2.21.2007221605270.13247@tstest-VirtualBox
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit 7b668c064e ("serial: 8250: Fix max baud limit in generic 8250
port") fixed limits of a baud rate setting for a generic 8250 port.
In other words since that commit the baud rate has been permitted to be
within [uartclk / 16 / UART_DIV_MAX; uartclk / 16], which is absolutely
normal for a standard 8250 UART port. But there are custom 8250 ports,
which provide extended baud rate limits. In particular the Mediatek 8250
port can work with baud rates up to "uartclk" speed.
Normally that and any other peculiarity is supposed to be handled in a
custom set_termios() callback implemented in the vendor-specific
8250-port glue-driver. Currently that is how it's done for the most of
the vendor-specific 8250 ports, but for some reason for Mediatek a
solution has been spread out to both the glue-driver and to the generic
8250-port code. Due to that a bug has been introduced, which permitted the
extended baud rate limit for all even for standard 8250-ports. The bug
has been fixed by the commit 7b668c064e ("serial: 8250: Fix max baud
limit in generic 8250 port") by narrowing the baud rates limit back down to
the normal bounds. Unfortunately by doing so we also broke the
Mediatek-specific extended bauds feature.
A fix of the problem described above is twofold. First since we can't get
back the extended baud rate limits feature to the generic set_termios()
function and that method supports only a standard baud rates range, the
requested baud rate must be locally stored before calling it and then
restored back to the new termios structure after the generic set_termios()
finished its magic business. By doing so we still use the
serial8250_do_set_termios() method to set the LCR/MCR/FCR/etc. registers,
while the extended baud rate setting procedure will be performed later in
the custom Mediatek-specific set_termios() callback. Second since a true
baud rate is now fully calculated in the custom set_termios() method we
need to locally update the port timeout by calling the
uart_update_timeout() function. After the fixes described above are
implemented in the 8250_mtk.c driver, the Mediatek 8250-port should
get back to normally working with extended baud rates.
Link: https://lore.kernel.org/linux-serial/20200701211337.3027448-1-danielwinkler@google.com
Fixes: 7b668c064e ("serial: 8250: Fix max baud limit in generic 8250 port")
Reported-by: Daniel Winkler <danielwinkler@google.com>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: stable <stable@vger.kernel.org>
Tested-by: Claire Chang <tientzu@chromium.org>
Link: https://lore.kernel.org/r/20200714124113.20918-1-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.
Deterministic algorithm:
For each file:
If not .svg:
For each line:
If doesn't contain `\bxmlns\b`:
For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`:
If both the HTTP and HTTPS versions
return 200 OK and serve the same content:
Replace HTTP with HTTPS.
Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Link: https://lore.kernel.org/r/20200718123840.19957-1-grandmaster@al2klimov.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Since commit 84af7a6194 ("checkpatch: kconfig: prefer 'help' over
'---help---'"), the number of '---help---' has been gradually
decreasing, but there are still more than 2400 instances.
This commit finishes the conversion. While I touched the lines,
I also fixed the indentation.
There are a variety of indentation styles found.
a) 4 spaces + '---help---'
b) 7 spaces + '---help---'
c) 8 spaces + '---help---'
d) 1 space + 1 tab + '---help---'
e) 1 tab + '---help---' (correct indentation)
f) 1 tab + 1 space + '---help---'
g) 1 tab + 2 spaces + '---help---'
In order to convert all of them to 1 tab + 'help', I ran the
following commend:
$ find . -name 'Kconfig*' | xargs sed -i 's/^[[:space:]]*---help---/\thelp/'
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Pull tty/serial driver updates from Greg KH:
"Here is the tty and serial driver updates for 5.8-rc1
Nothing huge at all, just a lot of little serial driver fixes, updates
for new devices and features, and other small things. Full details are
in the shortlog.
All of these have been in linux-next with no issues for a while"
* tag 'tty-5.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (67 commits)
tty: serial: qcom_geni_serial: Add 51.2MHz frequency support
tty: serial: imx: clear Ageing Timer Interrupt in handler
serial: 8250_fintek: Add F81966 Support
sc16is7xx: Add flag to activate IrDA mode
dt-bindings: sc16is7xx: Add flag to activate IrDA mode
serial: 8250: Support rs485 bus termination GPIO
serial: 8520_port: Fix function param documentation
dt-bindings: serial: Add binding for rs485 bus termination GPIO
vt: keyboard: avoid signed integer overflow in k_ascii
serial: 8250: Enable 16550A variants by default on non-x86
tty: hvc_console, fix crashes on parallel open/close
serial: imx: Initialize lock for non-registered console
sc16is7xx: Read the LSR register for basic device presence check
sc16is7xx: Allow sharing the IRQ line
sc16is7xx: Use threaded IRQ
sc16is7xx: Always use falling edge IRQ
tty: n_gsm: Fix bogus i++ in gsm_data_kick
tty: n_gsm: Remove unnecessary test in gsm_print_packet()
serial: stm32: add no_console_suspend support
tty: serial: fsl_lpuart: Use __maybe_unused instead of #if CONFIG_PM_SLEEP
...
Commit e8759ad17d ("serial: uapi: Add support for bus termination")
introduced the ability to enable rs485 bus termination from user space.
So far the feature is only used by a single driver, 8250_exar.c, using a
hardcoded GPIO pin specific to Siemens IOT2040 products.
Provide for a more generic solution by allowing specification of an
rs485 bus termination GPIO pin in the device tree: Amend the serial
core to retrieve the GPIO from the device tree (or ACPI table) and amend
the default ->rs485_config() callback for 8250 drivers to change the
GPIO on request from user space.
Perhaps 8250_exar.c can be converted to the generic approach in a
follow-up patch.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Link: https://lore.kernel.org/r/94c6c800d1ca9fa04766dd1d43a8272c5ad4bedd.1589811297.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Standard 8250 UART ports are designed in a way so they can communicate
with baud rates up to 1/16 of a reference frequency. It's expected from
most of the currently supported UART controllers. That's why the former
version of serial8250_get_baud_rate() method called uart_get_baud_rate()
with min and max baud rates passed as (port->uartclk / 16 / UART_DIV_MAX)
and ((port->uartclk + tolerance) / 16) respectively. Doing otherwise, like
it was suggested in commit ("serial: 8250_mtk: support big baud rate."),
caused acceptance of bauds, which was higher than the normal UART
controllers actually supported. As a result if some user-space program
requested to set a baud greater than (uartclk / 16) it would have been
permitted without truncation, but then serial8250_get_divisor(baud)
(which calls uart_get_divisor() to get the reference clock divisor) would
have returned a zero divisor. Setting zero divisor will cause an
unpredictable effect varying from chip to chip. In case of DW APB UART the
communications just stop.
Lets fix this problem by getting back the limitation of (uartclk +
tolerance) / 16 maximum baud supported by the generic 8250 port. Mediatek
8250 UART ports driver developer shouldn't have touched it in the first
place notably seeing he already provided a custom version of set_termios()
callback in that glue-driver which took into account the extended baud
rate values and accordingly updated the standard and vendor-specific
divisor latch registers anyway.
Fixes: 81bb549fdf ("serial: 8250_mtk: support big baud rate.")
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Long Cheng <long.cheng@mediatek.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: linux-mips@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mediatek@lists.infradead.org
Link: https://lore.kernel.org/r/20200506233136.11842-2-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We're about to amend uart_get_rs485_mode() to support a GPIO pin for
rs485 bus termination. Retrieving the GPIO descriptor may fail, so
allow uart_get_rs485_mode() to return an errno and change all callers
to check for failure.
The GPIO descriptor is going to be stored in struct uart_port. Pass
that struct to uart_get_rs485_mode() in lieu of a struct device and
struct serial_rs485, both of which are directly accessible from struct
uart_port.
A few drivers call uart_get_rs485_mode() before setting the struct
device pointer in struct uart_port. Shuffle those calls around where
necessary.
[Heiko Stuebner did the ar933x_uart.c portion, hence his Signed-off-by.]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/271e814af4b0db3bffbbb74abf2b46b75add4516.1589285873.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
If the call to uart_add_one_port() in serial8250_register_8250_port()
fails, a half-initialized entry in the serial_8250ports[] array is left
behind.
A subsequent reprobe of the same serial port causes that entry to be
reused. Because uart->port.dev is set, uart_remove_one_port() is called
for the half-initialized entry and bails out with an error message:
bcm2835-aux-uart 3f215040.serial: Removing wrong port: (null) != (ptrval)
The same happens on failure of mctrl_gpio_init() since commit
4a96895f74 ("tty/serial/8250: use mctrl_gpio helpers").
Fix by zeroing the uart->port.dev pointer in the probe error path.
The bug was introduced in v2.6.10 by historical commit befff6f5bf5f
("[SERIAL] Add new port registration/unregistration functions."):
https://git.kernel.org/tglx/history/c/befff6f5bf5f
The commit added an unconditional call to uart_remove_one_port() in
serial8250_register_port(). In v3.7, commit 835d844d1a ("8250_pnp:
do pnp probe before legacy probe") made that call conditional on
uart->port.dev which allows me to fix the issue by zeroing that pointer
in the error path. Thus, the present commit will fix the problem as far
back as v3.7 whereas still older versions need to also cherry-pick
835d844d1a.
Fixes: 835d844d1a ("8250_pnp: do pnp probe before legacy probe")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org # v2.6.10
Cc: stable@vger.kernel.org # v2.6.10: 835d844d1a: 8250_pnp: do pnp probe before legacy
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/b4a072013ee1a1d13ee06b4325afb19bda57ca1b.1589285873.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Pull tty/serial updates from Greg KH:
"Here is the big set of TTY / Serial patches for 5.7-rc1
Lots of console fixups and reworking in here, serial core tweaks
(doesn't that ever get old, why are we still creating new serial
devices?), serial driver updates, line-protocol driver updates, and
some vt cleanups and fixes included in here as well.
All have been in linux-next with no reported issues"
* tag 'tty-5.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (161 commits)
serial: 8250: Optimize irq enable after console write
serial: 8250: Fix rs485 delay after console write
vt: vt_ioctl: fix use-after-free in vt_in_use()
vt: vt_ioctl: fix VT_DISALLOCATE freeing in-use virtual console
tty: serial: make SERIAL_SPRD depend on COMMON_CLK
tty: serial: fsl_lpuart: fix return value checking
tty: serial: fsl_lpuart: move dma_request_chan()
ARM: dts: tango4: Make /serial compatible with ns16550a
ARM: dts: mmp*: Make the serial ports compatible with xscale-uart
ARM: dts: mmp*: Fix serial port names
ARM: dts: mmp2-brownstone: Don't redeclare phandle references
ARM: dts: pxa*: Make the serial ports compatible with xscale-uart
ARM: dts: pxa*: Fix serial port names
ARM: dts: pxa*: Don't redeclare phandle references
serial: omap: drop unused dt-bindings header
serial: 8250: 8250_omap: Add DMA support for UARTs on K3 SoCs
serial: 8250: 8250_omap: Work around errata causing spurious IRQs with DMA
serial: 8250: 8250_omap: Extend driver data to pass FIFO trigger info
serial: 8250: 8250_omap: Move locking out from __dma_rx_do_complete()
serial: 8250: 8250_omap: Account for data in flight during DMA teardown
...
Commit 7f9803072f ("serial: 8250: Support console on software emulated
rs485 ports") amended serial8250_console_write() with rs485 support, but
positioned the invocation of ->rs485_stop_tx() after re-enablement of
interrupts. The irq handler and ->console_write() are serialized with
the port spinlock, so no problem there, but due to the rs485 delay, the
irq handler may unnecessarily spin for a while. Avoid that by moving
->rs485_stop_tx() before re-enablement of interrupts, which also mirrors
the order at the beginning of serial8250_console_write().
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/019839cb1f61b01210b6ff9ac9f9079ca77f8411.1585319447.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
As per Advisory 27 of AM437x Silicon errata document, Spurious UART
interrupts may occur when DMA mode (FCR.DMA_MODE) is enabled. The
Interrupt Controller flags that a UART interrupt has occurred; however,
the associated IT_PENDING bit remains set to 1, indicating that no
interrupt is pending. Acknowledge the spurious interrupts for every
occurrence as workaround.
Errata is applicable to all TI SoCs with this IP.
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20200319110344.21348-6-vigneshr@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Although same 8250 compliant UART IP is reused across different SoC,
their integration wrt DMA varies greatly across SoCs. Therefore,
different SoC may need to use different FIFO trigger level for DMA
event and DMA configuration parameters. Provide a way to pass this
information via driver data. This is required to support UART DMA on
AM654/J721e SoCs.
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20200319110344.21348-5-vigneshr@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Terminate and flush DMA internal buffers, before pushing RX data to
higher layer. Otherwise, this will lead to data corruption, as driver
would end up pushing stale buffer data to higher layer while actual data
is still stuck inside DMA hardware and has yet not arrived at the
memory.
While at that, replace deprecated dmaengine_terminate_all() with
dmaengine_terminate_async().
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20200319110344.21348-2-vigneshr@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When port's throttle callback is called, it should stop pushing any more
data into TTY buffer to avoid buffer overflow. This means driver has to
stop HW from receiving more data and assert the HW flow control. For
UARTs with auto HW flow control (such as 8250_omap) manual assertion of
flow control line is not possible and only way is to allow RX FIFO to
fill up, thus trigger auto HW flow control logic.
Therefore make sure that 8250 generic IRQ handler does not drain data
when port is stopped (i.e UART_LSR_DR is unset in read_status_mask). Not
servicing, RX FIFO would trigger auto HW flow control when FIFO
occupancy reaches preset threshold, thus halting RX.
Since, error conditions in UART_LSR register are cleared just by reading
the register, data has to be drained in case there are FIFO errors, else
error information will lost.
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20200319103230.16867-2-vigneshr@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
It would be too tricky and error prone to allow DMA operations on
kernel console.
One of the concern is when DMA is a separate device, for example on
Intel CherryTrail platforms, and might need special work around to be
functional, see the commit
eebb3e8d8a ("ACPI / LPSS: override power state for LPSS DMA device")
for more information.
Another one is that kernel console is used in atomic context, e.g.
when printing crucial information to the user (Oops or crash),
and DMA may not serve due to power management complications
including non-atomic ACPI calls but not limited to it (see above).
Besides that, other concerns are described in the commit
84b40e3b57 ("serial: 8250: omap: Disable DMA for console UART")
done for OMAP UART and may be repeated here.
Disable any kind of DMA operations on kernel console due to above concerns.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200217114016.49856-7-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 <rmk+kernel@armlinux.org.uk>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200217114016.49856-6-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We need the vt fixes in here and it resolves a merge issue with
drivers/tty/vt/selection.c
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit e490c9144c ("tty: Add software emulated RS485 support for 8250")
introduced support to use RTS as an rs485 Transmit Enable signal if data
is transmitted through the tty layer.
Console messages bypass the tty layer and instead are emitted via
serial8250_console_write(). Amend that function to drive RTS as well,
allowing for a console on rs485 ports.
Note that serial8250_console_write() may be called concurrently to the
tty layer accessing the port. The two protect their accesses with the
port lock, but serial8250_console_write() may find RTS still being
asserted by the tty layer, in which case it shouldn't be deasserted
after the console message has been printed. Recognize such situations
by checking the em485->tx_stopped flag.
If a delay_rts_before_send or delay_rts_after_send has been specified,
serial8250_console_write() busy-waits for its duration. Optimizations
for those wait times are conceivable: E.g. if RTS is already asserted,
we could check whether em485->start_tx_timer is active and wait only
for the remaining expire time. But this would require calling into
the hrtimer infrastructure, which involves acquiring locks and
potentially reprogramming timer hardware. Such operations seem too
risky in the context of console printout, which needs to work even when
the kernel has crashed and emits a BUG splat. So I've gone with a
simplistic solution which just always waits for the full delay.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Matwey V. Kornilov <matwey@sai.msu.ru>
Link: https://lore.kernel.org/r/65edffce4670a19e598015c03cbe46f1ffd93e43.1582895077.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Amend 8250_bcm2835aux.c to support rs485 as introduced for 8250_omap.c
by commit e490c9144c ("tty: Add software emulated RS485 support for
8250").
The bcm2835aux differs from omap chips by inverting the meaning of RTS
in the MCR register: If the bit is clear, RTS is high. With omap, it's
apparently the other way round.
Moreover, omap achieves half-duplex mode by disabling the UART_IER_RDI
interrupt and clearing the RX FIFO when TX stops. This approach doesn't
work on bcm2835aux because the UART_LSR_DR bit is set even when
UART_IER_RDI is disabled. Consequently, serial8250_handle_irq() invokes
serial8250_rx_chars() to empty the FIFO and characters are received even
though the user requested half-duplex. Solve by disabling the receiver
using the non-standard CNTL register.
Cache that register in the driver's private data for performance. Set
the private data pointer before calling serial8250_register_8250_port()
to prevent a null pointer deref in case one of the rs485 callbacks is
invoked immediately after port registration.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Matwey V. Kornilov <matwey@sai.msu.ru>
Link: https://lore.kernel.org/r/dd86460e20a8f979b7272a0bde73640312b902b1.1582895077.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
