drm/solomon: Add SSD130x OLED displays SPI support

Hello,

This series adds a ssd130x-spi driver that provides a 4-wire SPI transport
support for SSD130x OLED controllers that can be accessed over a SPI bus.

The driver is quite similar to existing ssd130x-i2c driver that is used by
I2C controllers, but there is a difference in the protocol used by SSD130x
depending on the transport used. The details are in patch #4 description.

Patch #1 just makes the current ssd130x-i2c compatible strings in the DT
binding to be deprecated, and add new ones that don't have an "fb-i2c".

Patch #2 extends the DT binding with the properties needed to support SPI.

Patch #3 adds the new compatible strings to the OF device ID table in the
ssd130x-i2c DRM driver and deprecate the old ones.

Patch #4 moves the device info for the different SSD130x variants from
the ssd130x-i2c transport driver to the ssd130x core driver.

Finally patch #5 adds the ssd130x-spi DRM driver for the OLED controllers
that come with a 4-wire SPI interface, instead of an I2C interface.

This is a v4 that addresses the issues pointed out in v3.

Best regards,
Javier

Changes in v4:
- Add a description for the dc-gpios property for SPI (Geert Uytterhoeven)
- Export ssd13x_variants array using EXPORT_SYMBOL_NS_GPL() (Andy Shevchenko)
- Use MODULE_IMPORT_NS(DRM_SSD130X) in the ssd130x-i2c driver (Andy Shevchenko)
- Use MODULE_IMPORT_NS(DRM_SSD130X) in the ssd130x-spi driver (Andy Shevchenko)

Changes in v3:
- Drop the "sinowealth,sh1106-i2c", wasn't in a released version (Chen-Yu Tsai)
- Continue enforcing required properties for deprecated strings (Maxime Ripard)
- Add a comment to the properties required for SPI (Geert Uytterhoeven)
- Drop the "sinowealth,sh1106-i2c", wasn't in a released version (Chen-Yu Tsai)
- s/it/they in the commit description (Geert Uytterhoeven)
- Drop unnecessary blank line (Geert Uytterhoeven)
- Export variants array and use &info[ID] in device table (Andy Shevchenko)
- Drop ssd130x_spi_get_dc() helper and open code it (Geert Uytterhoeven)
- Export variants array and use &info[ID] in device table (Andy Shevchenko)
- Add Geert Uytterhoeven's Reviewed-by tag to patches.

Changes in v2:
- Drop the -i2c suffixes from the compatible strings too (Geert Uytterhoeven)
- Don't add compatible strings with an "-spi" suffix (Geert Uytterhoeven)
- Use the compatible strings that don't have "fb-i2c" (Geert Uytterhoeven).
- Drop ssd13x_variant_to_info() and just use the array index (Neil Armstrong).
- Add the same compatible strings than I2C (Geert Uytterhoeven)
- Add Mark Brown's Acked-by tag to all patches.

Javier Martinez Canillas (5):
  dt-bindings: display: ssd1307fb: Deprecate "-i2c" compatible strings
  dt-bindings: display: ssd1307fb: Extend schema for SPI controllers
  drm/solomon: Add ssd130x new compatible strings and deprecate old
    ones.
  drm/solomon: Move device info from ssd130x-i2c to the core driver
  drm/solomon: Add SSD130x OLED displays SPI support

 .../bindings/display/solomon,ssd1307fb.yaml   |  86 +++++++--
 drivers/gpu/drm/solomon/Kconfig               |   9 +
 drivers/gpu/drm/solomon/Makefile              |   1 +
 drivers/gpu/drm/solomon/ssd130x-i2c.c         |  64 +++----
 drivers/gpu/drm/solomon/ssd130x-spi.c         | 178 ++++++++++++++++++
 drivers/gpu/drm/solomon/ssd130x.c             |  35 +++-
 drivers/gpu/drm/solomon/ssd130x.h             |  14 ++
 7 files changed, 330 insertions(+), 57 deletions(-)
 create mode 100644 drivers/gpu/drm/solomon/ssd130x-spi.c

-- 
2.35.1