drm/panel: Add Magnachip D53E6EA8966 Panel Controller

From: Chris Morgan <[email protected]>

Add the Magnachip D53E6EA8966 panel IC controller for display panels such as the Samsung AMS495QA01 panel as found on the Anbernic RG503. This panel uses DSI to receive video signals, but 3-wire SPI to receive command signals using DBI.

Changes since V11:
- Added a "Co-developed-by" tag for Maya to capture her contributions correctly.

Changes since V10:
- Guarded definition in drm_of.h with an additional #if statement.
- Narrowed focus of drm_of_get_dsi_bus() to only return dsi_host (no longer populates node on the mipi_dsi_device_info struct).

Changes since V9:
- Set an ifdef to not add the drm_of_get_dsi_bus when MIPI_DSI is not part of the current kernel config.
- Made "info" optional in the drm_of_get_dsi_bus() function.

Changes since V8:
- Set "placeholder" drm_of_get_dsi_bus in drm_of.h to static inline to hopefully eliminate the reported errors once and for all. Tested with 4 different kernel configurations provided by Intel's kernel test robot and no new warnings or errors were introduced.

Changes since V7:
- Removed Linus Walleij review note due to substantial changes.
- Corrected documentation of drm_of_get_dsi_bus function.
- Updated the drm_of_get_dsi_bus function to return pointer to mipi_dsi_host and use ERR_PTR macros.
- Refactored drm_panel_funcs so that the prepare function calls panel specific function for init sequence and uses generic functions otherwise.
- Renamed non-panel specific functions.
- Changed backlight value to int instead of u32.
- Corrected brightness function to use backlight_get_brightness().
- Fix an error reported when CONFIG_OF is selected but CONFIG_DRM_MIPI_DSI is not. Add an if function to drm_of_get_dsi_bus function to return -EINVAL in this instance.

Changes since V6:
- Fixed a trivial error with definition of drm_of_get_dsi_bus().

Changes since V5:
- Reverted dt binding documentation name back to samsung,ams495qa01.yaml.
- Removed no longer needed of_graph.h header file.
- Added backlight as a dependency.

Changes since V4:
- Renamed driver from the panel model to the panel IC controller per DRM team.
- Added a drm_of helper function of drm_of_get_dsi_bus() to handle finding and populating the DSI node when the DSI node is not the parent of the DSI controlled display.
- Converted the documented commands to constants to make it more readable.
- Reset GPIO is now required and documented as GPIO_ACTIVE_LOW.
- Removed "prepared" logic from panel.

Changes since V3:
- Updated documentation to add spi-peripheral-props.yaml per updates
made for similar devices. Note that I removed a "Reviewed-by" tag
from Rob Herring since this change probably needs to be confirmed.
- Added binding for RG503, since this device is now accepted with this
request: https://lore.kernel.org/linux-rockchip/[email protected]/

Changes since V2:
- Added 50hz mode at request of userspace devs.
- Renamed "dupa" to panel name. Good catch Maya.
- Added Maya's Signed-off-by.
- Removed check for max backlight, since it is already done by backlight_device_set_brightness.
- Fixed minor formatting issues on devicetree binding documentation and added port to provided example.

Changes since V1:
- Removed errant reference to backlight in documentation. This is an OLED panel.
- Made elvss regulator optional. In my case its hard wired and not controllable.
- Added "prepared" enum to track panel status to prevent unbalanced regulator enable/disable.

Chris Morgan (4):
drm: of: Add drm_of_get_dsi_bus helper function
dt-bindings: display: panel: Add Samsung AMS495QA01 drm/panel: Add Magnachip D53E6EA8966 Panel Driver
arm64: dts: rockchip: add display to RG503

 .../display/panel/samsung,ams495qa01.yaml     |  57 ++
 .../dts/rockchip/rk3566-anbernic-rg503.dts    |  55 ++
 drivers/gpu/drm/drm_of.c                      |  51 ++
 drivers/gpu/drm/panel/Kconfig                 |  11 +
 drivers/gpu/drm/panel/Makefile                |   1 +
 .../drm/panel/panel-magnachip-d53e6ea8966.c   | 522 ++++++++++++++++++
 include/drm/drm_of.h                          |  12 +
 7 files changed, 709 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/panel/samsung,ams495qa01.yaml
 create mode 100644 drivers/gpu/drm/panel/panel-magnachip-d53e6ea8966.c

2.34.1