[PATCH v4 0/5] Add support for PinePhone LCD panel

[Ondrej Jirman]

This patchset adds support for the LCD panel of PinePhone.

The first 3 patches are for the panel itself, and the last 2 patches are
for enabling it on PinePhone.

I've tested this on PinePhone 1.0 and 1.2.

Please take a look.

thank you and regards,
  Ondrej Jirman

Changes in v4:
- use ->type from the mode instead of hardcoding (Samuel)
- move init_sequence to ->prepare (Samuel)
- move anti-flicker delay to ->enable, explain it (Samuel)
- add enter_sleep after display_off (Samuel)
- drop ->disable (move code to ->unprepare)
- add ID bytes dumping (Linus)
  (I can't test it since allwinner DSI driver has a broken
   dcs_read function, and I didn't manage to fix it.)
- document magic bytes (Linus)
- assert reset during powerup
- cleanup powerup timings according to the datasheet

Changes in v3:
- Panel driver renamed to the name of the LCD controller
- Re-organize the driver slightly to more easily support more panels
  based on the same controller.
- Add patch to enable the touchscreen to complete the LCD support
  on PinePhone.
- Dropped the "DSI fix" patch (the driver seems to work for me without it)
- Improved brightness levels handling:
  - PinePhone 1.0 uses default levels generated by the driver
  - On PinePhone 1.1 duty cycles < 20% lead to black screen, so
    default levels can't be used. Martijn Braam came up with a
    list of duty cycle values that lead to perception of linear
    brigtness level <-> light intensity on PinePhone 1.1
- There was some feedback on v2 about this being similar to st7701.
  It's only similar in name. Most of the "user commands" are different,
  so I opted to keep this in a new driver instead of creating st770x.
  
  Anyone who likes to check the differences, here are datasheets:

  - https://megous.com/dl/tmp/ST7703_DS_v01_20160128.pdf
  - https://megous.com/dl/tmp/ST7701.pdf

Changes in v2:
- DT Example fix.
- DT Format fix.
- Raised copyright info to 2020.
- Sort panel operation functions.
- Sort inclusion.


-- For phone owners: --

There's an open question on how to set the backlight brightness values
on post 1.0 revision phone, since lower duty cycles (< 10-20%) lead
to backlight being black. It would be nice if more people can test
the various backlight levels on 1.1 and 1.2 revision with this change
in dts:

       brightness-levels = <0 1000>;
       num-interpolated-steps = <1000>;

and report at what brightness level the backlight turns on. So far it
seems this has a wide range. Lowest useable duty cycle for me is ~7%
on 1.2 and for Martijn ~20% on 1.1.

Icenowy Zheng (4):
  dt-bindings: vendor-prefixes: Add Xingbangda
  dt-bindings: panel: Add binding for Xingbangda XBD599 panel
  drm: panel: Add Xingbangda XBD599 panel (ST7703 controller)
  arm64: dts: sun50i-a64-pinephone: Enable LCD support on PinePhone

Ondrej Jirman (1):
  arm64: dts: sun50i-a64-pinephone: Add touchscreen support

 .../display/panel/sitronix,st7703.yaml        |  63 +++
 .../devicetree/bindings/vendor-prefixes.yaml  |   2 +
 .../allwinner/sun50i-a64-pinephone-1.1.dts    |  19 +
 .../dts/allwinner/sun50i-a64-pinephone.dtsi   |  54 ++
 drivers/gpu/drm/panel/Kconfig                 |  10 +
 drivers/gpu/drm/panel/Makefile                |   1 +
 drivers/gpu/drm/panel/panel-sitronix-st7703.c | 535 ++++++++++++++++++
 7 files changed, 684 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/panel/sitronix,st7703.yaml
 create mode 100644 drivers/gpu/drm/panel/panel-sitronix-st7703.c

-- 
2.27.0