[RFC,0/2] Add DRM panel driver for Ilitek ILI9341 based panels in parallel RGB mode

Message

Josef Luštický March 4, 2019, 12:50 p.m. UTC

These patches add panel driver for ili9341-based panels in parallel RGB mode.
The driver was developed for DispleyTech DT024CTFT LCD panel [1] which features ILI9341 chip [2].
The driver was tested on the Allwinner A13 (sun5i) platform.

The driver supports 240x320 pixel resolution with 18-bit RGB (6 wires per color)
and SPI control bus with Data/Command GPIO pin:
DisplayTech DT024CTFT panel is configured with the IM[0:3] pins
set to "1110" - see page 10 in datasheet [2].

The Data/Command GPIO is optional, however at the moment the driver requires it:
The display itself is capable of 9-bit SPI without the Data/Command GPIO.
Support for such configuration can be added later to the driver.

Optional HW reset gpio can be specified, otherwise SW reset command is used
during the initialization.

The ILI9341 displays have two command sets:
Level 1 conforms to MIPI specs
Level 2 is outside the MIPI specs - custom defines are used in the driver

The ILI9341 supports various RGB modes (e.g. NVSYNC, DE_LOW, clock freq, etc.),
however values that are presented in the ILI9341 datasheet [2] are used
by the driver in struct drm_display_mode.


General note on ILI9341-based displays:
The ILI9341 chip can be used in parallel RGB with SPI control
or in SPI only mode where the image data itself is also transferred via SPI.
This driver supports parallel RGB displays - it works with displays wired with 18-bit RGB input,
it does not support SPI data mode (i.e. Multi-inno mi0283qt or Adafruit yx240qv29 are not supported by this driver).
The SPI data mode is naturally much slower than the parallel RGB mode.

General note on DisplayTech DT024CTFT panel:
The panel supports different configuation options (18/16/6-bit RGB or 9/8-bit SPI) depending on the IM[0:3] wiring.
To keep this patch small for reveiw, at the moment only 18-bit RGB mode and 8-bit SPI with Data/Command GPIO
is supported by this driver.


I kindly ask you for a patch review.

Links to datasheet:
[1] https://www.displaytech-us.com/sites/default/files/display-data-sheet/DT024CTFT-v10_0.pdf
[2] https://cdn-shop.adafruit.com/datasheets/ILI9341.pdf

Best regards,
Josef Lusticky

Josef Lusticky (2):
  drm/panel: Add Ilitek ILI9341 parallel RGB panel driver
  dt-bindings: panel: Add Ilitek ILI9341 panel documentation

 .../bindings/display/panel/ilitek,ili9341.txt |  33 ++
 MAINTAINERS                                   |   6 +
 drivers/gpu/drm/panel/Kconfig                 |   7 +
 drivers/gpu/drm/panel/Makefile                |   1 +
 drivers/gpu/drm/panel/panel-ilitek-ili9341.c  | 320 ++++++++++++++++++
 5 files changed, 367 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/panel/ilitek,ili9341.txt
 create mode 100644 drivers/gpu/drm/panel/panel-ilitek-ili9341.c