linux.git/drivers/tty/serial/serial_core.c, branch v6.1

serial: Deassert Transmit Enable on probe in driver-specific way

2022-09-25T07:28:57+00:00

When a UART port is newly registered, uart_configure_port() seeks to
deassert RS485 Transmit Enable by setting the RTS bit in port->mctrl.
However a number of UART drivers interpret a set RTS bit as *assertion*
instead of deassertion:  Affected drivers include those using
serial8250_em485_config() (except 8250_bcm2835aux.c) and some using
mctrl_gpio (e.g. imx.c).

Since the interpretation of the RTS bit is driver-specific, it is not
suitable as a means to centrally deassert Transmit Enable in the serial
core.  Instead, the serial core must call on drivers to deassert it in
their driver-specific way.  One way to achieve that is to call
->rs485_config().  It implicitly deasserts Transmit Enable.

So amend uart_configure_port() and uart_resume_port() to invoke
uart_rs485_config().  That allows removing calls to uart_rs485_config()
from drivers' ->probe() hooks and declaring the function static.

Skip any invocation of ->set_mctrl() if RS485 is enabled.  RS485 has no
hardware flow control, so the modem control lines are irrelevant and
need not be touched.  When leaving RS485 mode, reset the modem control
lines to the state stored in port->mctrl.  That way, UARTs which are
muxed between RS485 and RS232 transceivers drive the lines correctly
when switched to RS232.  (serial8250_do_startup() historically raises
the OUT1 modem signal because otherwise interrupts are not signaled on
ancient PC UARTs, but I believe that no longer applies to modern,
RS485-capable UARTs and is thus safe to be skipped.)

imx.c modifies port->mctrl whenever Transmit Enable is asserted and
deasserted.  Stop it from doing that so port->mctrl reflects the RS232
line state.

8250_omap.c deasserts Transmit Enable on ->runtime_resume() by calling
->set_mctrl().  Because that is now a no-op in RS485 mode, amend the
function to call serial8250_em485_stop_tx().

fsl_lpuart.c retrieves and applies the RS485 device tree properties
after registering the UART port.  Because applying now happens on
registration in uart_configure_port(), move retrieval of the properties
ahead of uart_add_one_port().

Link: https://lore.kernel.org/all/20220329085050.311408-1-matthias.schiffer@ew.tq-group.com/
Link: https://lore.kernel.org/all/8f538a8903795f22f9acc94a9a31b03c9c4ccacb.camel@ginzinger.com/
Fixes: d3b3404df318 ("serial: Fix incorrect rs485 polarity on uart open")
Cc: stable@vger.kernel.org # v4.14+
Reported-by: Matthias Schiffer 
Reported-by: Roosen Henri 
Tested-by: Matthias Schiffer 
Reviewed-by: Ilpo Järvinen 
Signed-off-by: Lukas Wunner 
Link: https://lore.kernel.org/r/2de36eba3fbe11278d5002e4e501afe0ceaca039.1663863805.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman

tty: Make ->set_termios() old ktermios const

2022-08-30T12:22:35+00:00

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

Reviewed-by: Andy Shevchenko 
Signed-off-by: Ilpo Järvinen 
Link: https://lore.kernel.org/r/20220816115739.10928-9-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: Make ->set_termios() old ktermios const

2022-08-30T12:22:35+00:00

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

Reviewed-by: Andy Shevchenko 
Signed-off-by: Ilpo Järvinen 
Link: https://lore.kernel.org/r/20220816115739.10928-7-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

tty: move from strlcpy with unused retval to strscpy

2022-08-30T12:21:59+00:00

Follow the advice of the below link and prefer 'strscpy' in this
subsystem. Conversion is 1:1 because the return value is not used.
Generated by a coccinelle script.

Link: https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/
Reviewed-by: Jiri Slaby 
Signed-off-by: Wolfram Sang 
Link: https://lore.kernel.org/r/20220818210113.7469-1-wsa+renesas@sang-engineering.com
Signed-off-by: Greg Kroah-Hartman

Merge tag 'tty-6.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

2022-08-08T18:31:40+00:00

Pull tty / serial driver updates from Greg KH:
 "Here is the big set of tty and serial driver changes for 6.0-rc1.

  It was delayed from last week as I wanted to make sure the last commit
  here got some good testing in linux-next and elsewhere as it seemed to
  show up only late in testing for some reason.

  Nothing major here, just lots of cleanups from Jiri and Ilpo to make
  the tty core cleaner (Jiri) and the rs485 code simpler to use (Ilpo).

  Also included in here is the obligatory n_gsm updates from Daniel
  Starke and lots of tiny driver updates and minor fixes and tweaks for
  other smaller serial drivers.

  All of these have been in linux-next for a while with no reported
  problems"

* tag 'tty-6.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (186 commits)
  tty: serial: qcom-geni-serial: Fix %lu -> %u in print statements
  tty: amiserial: Fix comment typo
  tty: serial: document uart_get_console()
  tty: serial: serial_core, reformat kernel-doc for functions
  Documentation: serial: link uart_ops properly
  Documentation: serial: move GPIO kernel-doc to the functions
  Documentation: serial: dedup kernel-doc for uart functions
  Documentation: serial: move uart_ops documentation to the struct
  dt-bindings: serial: snps-dw-apb-uart: Document Rockchip RV1126
  serial: mvebu-uart: uart2 error bits clearing
  tty: serial: fsl_lpuart: correct the count of break characters
  serial: stm32: make info structs static to avoid sparse warnings
  serial: fsl_lpuart: zero out parity bit in CS7 mode
  tty: serial: qcom-geni-serial: Fix get_clk_div_rate() which otherwise could return a sub-optimal clock rate.
  serial: 8250_bcm2835aux: Add missing clk_disable_unprepare()
  tty: vt: initialize unicode screen buffer
  serial: remove VR41XX serial driver
  serial: 8250: lpc18xx: Remove redundant sanity check for RS485 flags
  serial: 8250_dwlib: remove redundant sanity check for RS485 flags
  dt_bindings: rs485: Correct delay values
  ...

tty: serial: document uart_get_console()

2022-07-28T08:37:42+00:00

This was the only function mentioned in the text, but was neither linked
nor documented. So document and link it, so that hyperlinking works in
the text.

Signed-off-by: Jiri Slaby 
Link: https://lore.kernel.org/r/20220728061056.20799-6-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman

tty: serial: serial_core, reformat kernel-doc for functions

2022-07-28T08:37:42+00:00

There are many annotated functions in serial_core.c, but they do not
completely conform to the kernel-doc style. So reformat them and link
them from the Documentation.

Signed-off-by: Jiri Slaby 
Link: https://lore.kernel.org/r/20220728061056.20799-5-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman

Documentation: serial: dedup kernel-doc for uart functions

2022-07-28T08:37:42+00:00

Some of the serial (uart_*) functions are documented twice. Once as
kernel-doc along their sources and once in Documentation. So deduplicate
these texts, merge them into kernel-doc in the sources, and link them
using kernel-doc: from the Documentation.

To be properly linked and rendered, tabulators had to be removed from
the comments.

Signed-off-by: Jiri Slaby 
Link: https://lore.kernel.org/r/20220728061056.20799-2-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman

serial: core: sanitize RS485 delays read from device tree

2022-07-14T14:34:24+00:00

Currently the RTS delays set via device tree are not clamped to a maximum
value although the device tree bindings documentation for RS485 claims that
only a maximum of 1000 msecs is allowed.

So clamp the values to avoid arbitrary high delay settings. However clamp
the values to 100 instead of 1000 msecs to be consistent which the maximum
that is allowed when setting the delays from userspace via the UART ioctl
TIOCSRS485.

Signed-off-by: Lino Sanfilippo 
Link: https://lore.kernel.org/r/20220710164442.2958979-6-LinoSanfilippo@gmx.de
Signed-off-by: Greg Kroah-Hartman

serial: core: move sanitizing of RS485 delays into own function

2022-07-14T14:34:24+00:00

Move the sanitizing of RS485 delays out of uart_sanitize_serial_rs485()
into the new function uart_sanitize_serial_rs485_delays().

Reviewed-by: Ilpo Järvinen 
Signed-off-by: Lino Sanfilippo 
Link: https://lore.kernel.org/r/20220710164442.2958979-5-LinoSanfilippo@gmx.de
Signed-off-by: Greg Kroah-Hartman