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SubjectRe: [PATCH 3/9] drm/panel: simple: make it possible to override LCD bus format
On Wed, Oct 11, 2017 at 01:23:35PM +0200, Lothar Waßmann wrote:
> The baseboards for the Ka-Ro electronics series of i.MX modules
> use a 24bit LCD interface, no matter what LCD bus width the SoC on the
> module provides and what the LCD panel expects. LCDs with 6bit per color
> will ignore the 2 LSBs of each color lane, and modules using a SoC
> that provides only 6bit per color, drive the display information on the
> 6 MSBs of each color lane and tie the 2 LSBs of each color lane to GND.
>
> Thus, no matter what combination of LCD and SoC is used, the LCD port
> can be used without shuffling bit lanes by always configuring the LCD
> output to 24bit mode.

Thanks for providing good reasoning as to why this is needed.

>
> Add a function to handle certain quirks of the LCD interface to the
> panel driver to be able to override the bus format specified in a
> panel's display_mode.
>
> Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
> ---
> .../bindings/display/panel/simple-panel.txt | 2 ++
> drivers/gpu/drm/panel/panel-simple.c | 40 +++++++++++++++++++++-
> 2 files changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/display/panel/simple-panel.txt b/Documentation/devicetree/bindings/display/panel/simple-panel.txt
> index 1341bbf..e2308c3 100644
> --- a/Documentation/devicetree/bindings/display/panel/simple-panel.txt
> +++ b/Documentation/devicetree/bindings/display/panel/simple-panel.txt
> @@ -7,6 +7,8 @@ Optional properties:
> - ddc-i2c-bus: phandle of an I2C controller used for DDC EDID probing
> - enable-gpios: GPIO pin to enable or disable the panel
> - backlight: phandle of the backlight device attached to the panel
> +- bus-format-override: override the bus_format setting of the panel's
> + display_mode settings

You need to define valid values here.

However, we also have this proposal[1]. Please align to a common one.
BTW, we don't need another common panel binding file that [1] added. We
already have panel-dpi.txt for parallel interface panels. And
personally, I'd like to see simple-panel.txt disappear.

Rob

[1] https://patchwork.ozlabs.org/patch/823104/

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