[PATCH v1 0/4] drm: mxsfb: Support LCDIF interface pixel format

[Francesco Dolcini <francesco@dolcini.it>]

From: Francesco Dolcini <francesco.dolcini@toradex.com>

The LCDIF data bus format describes how color component bits are assigned
to the physical LCD_DATA pins. This is a property of the LCDIF-to-display
wiring and can differ from the input format advertised by the downstream
panel or bridge.

Such a distinction is required when a narrower LCDIF bus is connected to
a wider display interface. For example, an 18-bit or 16-bit LCDIF bus can
drive a 24-bit display by wiring the available color bits to the
appropriate display inputs. Configuring LCDIF from the display's 24-bit
format in this case selects the wrong LCD_DATABUS_WIDTH mode, changing the
color-bit assignment on the LCD_DATA pins and resulting in incorrect
colors.

Add the optional interface-pix-fmt property to the LCDIF binding and make
the mxsfb driver use it in preference to the format reported by the
downstream display. When the property is absent, the existing behavior is
preserved.

This follows the approach already used by the i.MX IPUv3 parallel display
driver in drivers/gpu/drm/imx/ipuv3/parallel-display.c.

Set the interface format for the Colibri iMX6ULL and Colibri iMX7 boards,
which route an 18-bit LCD interface.

Francesco Dolcini (4):
  dt-bindings: lcdif: Add interface pixel format
  drm: mxsfb: Allow optional LCDIF interface format override
  ARM: dts: imx6ull-colibri: Set LCDIF format
  ARM: dts: imx7-colibri: Set LCDIF format

 .../devicetree/bindings/display/fsl,lcdif.yaml   |  7 +++++++
 arch/arm/boot/dts/nxp/imx/imx6ull-colibri.dtsi   |  1 +
 arch/arm/boot/dts/nxp/imx/imx7-colibri.dtsi      |  1 +
 drivers/gpu/drm/mxsfb/mxsfb_drv.c                | 16 ++++++++++++++++
 drivers/gpu/drm/mxsfb/mxsfb_drv.h                |  2 ++
 drivers/gpu/drm/mxsfb/mxsfb_kms.c                |  8 ++++++++
 6 files changed, 35 insertions(+)

-- 
2.47.3