[v7,0/9] serial: sc16is7xx: fix GPIO regression and rs485 improvements

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

Hello,
this patch series mainly fixes a GPIO regression and improve RS485 flags and
properties detection from DT.

It now also includes various small fixes and improvements that were previously
sent as separate patches, but that made testing everything difficult.

Patch 1 fixes an issue with init of first port during probing.

Patch 2 fixes an issue when debugging IOcontrol register, but it is also
necessary for patch "fix regression with GPIO configuration" to work.

Patch 3 is a refactor of GPIO registration code in preparation for patch 5.

Patches 4 and 5 fix a GPIO regression by (re)allowing to choose GPIO function
for GPIO pins shared with modem status lines.

Patch 6 fixes a bug with the output value when first setting the GPIO direction.

Patch 7 allows to read common rs485 device-tree flags and properties.

Patch 8 introduces a delay after a reset operation to respect datasheet
timing recommandations.

Patch 9 improves comments about chip variants.

I have tested the changes on a custom board with two SC16IS752 DUART using a
Variscite IMX8MN NANO SOM.

Thank you.

Link: [v1] https://lkml.org/lkml/2023/5/17/967
      [v1] https://lkml.org/lkml/2023/5/17/777
      [v1] https://lkml.org/lkml/2023/5/17/780
      [v1] https://lkml.org/lkml/2023/5/17/785
      [v1] https://lkml.org/lkml/2023/5/17/1311
      [v2] https://lkml.org/lkml/2023/5/18/516
      [v3] https://lkml.org/lkml/2023/5/25/7
      [v4] https://lkml.org/lkml/2023/5/29/656
      [v5] https://lkml.org/lkml/2023/6/1/1046
      [v6] https://lkml.org/lkml/2023/6/1/1328

Changes for V3:
- Integrated all patches into single serie to facilitate debugging and tests.
- Reduce number of exported GPIOs depending on new property
  nxp,modem-control-line-ports
- Added additional example in DT bindings

Changes for V4:
- Increase reset post delay to relax scheduler.
- Put comments patches at the end.
- Remove Fixes tag for patch "mark IOCONTROL register as volatile".
- Improve commit messages after reviews.
- Fix coding style issues after reviews.
- Change GPIO registration to always register the maximum number of GPIOs
  supported by the chip, but maks-out GPIOs declared as modem control lines.
- Add patch to refactor GPIO registration.
- Remove patch "serial: sc16is7xx: fix syntax error in comments".
- Remove patch "add dump registers function"

Changes for V5:
- Change patch order to facilitate stable backport(s).
- Change duplicate device addresses in DT binding examples.
- Use GENMASK for bit masks.
- Replace of_property_for_each_u32() with device_property_read_u32_array
- Add "Cc: stable..." tags

Changes for V6:
- Fix compilation bug introduced by patch 3

Changes for V7:
- Minor changes and coding style fixes after review for
  patch 5 "fix regression with GPIO configuration".

Hugo Villeneuve (9):
  serial: sc16is7xx: fix broken port 0 uart init
  serial: sc16is7xx: mark IOCONTROL register as volatile
  serial: sc16is7xx: refactor GPIO controller registration
  dt-bindings: sc16is7xx: Add property to change GPIO function
  serial: sc16is7xx: fix regression with GPIO configuration
  serial: sc16is7xx: fix bug when first setting GPIO direction
  serial: sc16is7xx: add call to get rs485 DT flags and properties
  serial: sc16is7xx: add post reset delay
  serial: sc16is7xx: improve comments about variants

 .../bindings/serial/nxp,sc16is7xx.txt         |  46 +++++
 drivers/tty/serial/sc16is7xx.c                | 169 +++++++++++++-----
 2 files changed, 175 insertions(+), 40 deletions(-)


base-commit: 9e87b63ed37e202c77aa17d4112da6ae0c7c097c