[v2,00/12] Add RS485 support to DW UART

This patchset adds RS-485 support to the DW UART driver. The patchset
has two main parts. The first part adds HW support for RS-485 itself
in various modes of operation and the second part focuses on enabling
9th bit addressing mode that can be used on a multipoint RS-485
communications line.

To configure multipoint addressing, ADDRB flag is added to termios
and two new IOCTLs are added into serial core. Lukas Wunner brought up
during v1 review that if this addressing is only going to be used with
RS-485, doing it within rs485_config would avoid having to add those
IOCTLs. There was some counterexample w/o further details mentioned for
RS-232 usage by Andy Shevchenko. I left the IOCTL approach there but if
somebody has further input on this, please voice it as it is user-space
facing API.

I decided to rewrite the UART_CAP_NOTEMT patch from scratch myself
based on Uwe Kleine-König's earlier suggestion and include it to this
series. To make waiting for a single character easy and to avoid
storing it per purpose in the uart drivers, I decided to add
frame_time into uart_port. It turned out to beneficial also for serial
core which had to reverse calculate it from uart_port->timeout). I was
thinking of removing uart_port->timeout entirely and derive the value
timeout from frame_time and fifosize where needed but I was not sure
if that's ok to do lockingwise (not that fifosize is a variable that
is expected to change so maybe I'm just being too cautious).

I added some sketch on the ACPI enumeration file to satisfy Andy's
request but I really don't know much about what should be put there.
Please check it out and comment if I managed to make a mess out of it.

I'm aware of the RS485 changes Lino Sanfilippo recently posted
to linux-serial list which will make one assignment in the patchset
redundant. I'll make the adjustment if those get applied into
upstream.

Cc: linux-api@vger.kernel.org

v1 -> v2:
- Add uart_port->frame_time to avoid the need to store it per purpose
- Included NOTEMT patch rewritten from scratch
- Merge HW half & full-duplex patches
- Detect RS485 HW using RE_EN register write+read
- Removed SER_RS485_SW_RX_OR_TX
- Relocated/renamed RE polarity DT prop
- Use SER_RS485_RTS_ON_SEND rather than DT prop directly
- Removed DE polarity prop, it is still configurable but with rts one instead
- Make DE active-high by default in dwlib
- Don't unnecessarily clear DE/RE_EN for non-RS485 mode
- Prevent ADDRB and addrmode desync for RS485->RS232 transition
- Added ACPI enumeration doc
- Changed -EINVAL to -ENOTTY if no set/get_addr handler is present
- Clear ADDRB in set_termios of a few more drivers
- Added filtering for addresses to avoid them leaking into data stream
- Reworded comments & commit messages as requested

Ilpo Järvinen (12):
  serial: Store character timing information to uart_port
  serial: 8250: Handle UART without interrupt on TEMT
  serial: 8250_dwlib: RS485 HW half & full duplex support
  serial: 8250_dwlib: Implement SW half duplex support
  dt_bindings: rs485: Add receiver enable polarity
  ACPI / property: Document RS485 _DSD properties
  serial: termbits: ADDRB to indicate 9th bit addressing mode
  serial: General support for multipoint addresses
  serial: 8250: make saved LSR larger
  serial: 8250: create lsr_save_mask
  serial: 8250_lpss: Use 32-bit reads
  serial: 8250_dwlib: Support for 9th bit multipoint addressing

 .../devicetree/bindings/serial/rs485.yaml     |   5 +
 .../driver-api/serial/serial-rs485.rst        |  23 +-
 .../firmware-guide/acpi/enumeration.rst       |  25 ++
 arch/alpha/include/uapi/asm/ioctls.h          |   3 +
 arch/alpha/include/uapi/asm/termbits.h        |   1 +
 arch/mips/include/uapi/asm/ioctls.h           |   3 +
 arch/mips/include/uapi/asm/termbits.h         |   1 +
 arch/parisc/include/uapi/asm/ioctls.h         |   3 +
 arch/parisc/include/uapi/asm/termbits.h       |   1 +
 arch/powerpc/include/uapi/asm/ioctls.h        |   3 +
 arch/powerpc/include/uapi/asm/termbits.h      |   1 +
 arch/sh/include/uapi/asm/ioctls.h             |   3 +
 arch/sparc/include/uapi/asm/ioctls.h          |   3 +
 arch/sparc/include/uapi/asm/termbits.h        |   1 +
 arch/xtensa/include/uapi/asm/ioctls.h         |   3 +
 drivers/char/pcmcia/synclink_cs.c             |   2 +
 drivers/ipack/devices/ipoctal.c               |   2 +
 drivers/mmc/core/sdio_uart.c                  |   2 +
 drivers/net/usb/hso.c                         |   3 +-
 drivers/s390/char/tty3270.c                   |   3 +
 drivers/staging/greybus/uart.c                |   2 +
 drivers/tty/amiserial.c                       |   6 +-
 drivers/tty/moxa.c                            |   1 +
 drivers/tty/mxser.c                           |   1 +
 drivers/tty/serial/8250/8250.h                |   1 +
 drivers/tty/serial/8250/8250_core.c           |   6 +-
 drivers/tty/serial/8250/8250_dwlib.c          | 232 +++++++++++++++++-
 drivers/tty/serial/8250/8250_dwlib.h          |   5 +
 drivers/tty/serial/8250/8250_lpss.c           |   2 +-
 drivers/tty/serial/8250/8250_port.c           |  42 ++--
 drivers/tty/serial/serial_core.c              |  76 +++++-
 drivers/tty/synclink_gt.c                     |   2 +
 drivers/tty/tty_ioctl.c                       |   2 +
 drivers/usb/class/cdc-acm.c                   |   2 +
 drivers/usb/serial/usb-serial.c               |   6 +-
 include/linux/serial_8250.h                   |   7 +-
 include/linux/serial_core.h                   |   7 +
 include/uapi/asm-generic/ioctls.h             |   3 +
 include/uapi/asm-generic/termbits.h           |   1 +
 include/uapi/linux/serial.h                   |   8 +
 net/bluetooth/rfcomm/tty.c                    |   2 +
 41 files changed, 470 insertions(+), 35 deletions(-)

On Mon, Apr 4, 2022 at 10:29 AM Ilpo Järvinen
<ilpo.jarvinen@linux.intel.com> wrote:

>
>  #define CLOCAL 00100000
> +#define ADDRB  010000000               /* address bit */
>  #define CMSPAR   010000000000          /* mark or space (stick) parity */
>  #define CRTSCTS          020000000000          /* flow control */
>
> diff --git a/arch/mips/include/uapi/asm/termbits.h b/arch/mips/include/uapi/asm/termbits.h
> index dfeffba729b7..e7ea31cfec78 100644
> --- a/arch/mips/include/uapi/asm/termbits.h
> +++ b/arch/mips/include/uapi/asm/termbits.h
> @@ -181,6 +181,7 @@ struct ktermios {
>  #define         B3000000 0010015
>  #define         B3500000 0010016
>  #define         B4000000 0010017
> +#define ADDRB    0020000       /* address bit */
>  #define CIBAUD   002003600000  /* input baud rate */
>  #define CMSPAR   010000000000  /* mark or space (stick) parity */
>  #define CRTSCTS          020000000000  /* flow control */

It looks like the top bits are used the same way on all architectures
already, while the bottom bits of the flag differ. Could you pick
the next free bit from the top to use the same value 04000000000
everywhere?

        Arnd