Re: [PATCH 3/6] dt-bindings: display: add data-enable polarity property

Laurent Pinchart
2018-09-05T20:50:21Z

Hi Stefan,

On Wednesday, 5 September 2018 21:10:08 EEST Stefan Agner wrote:
> On 05.09.2018 00:07, Laurent Pinchart wrote:
> > On Wednesday, 5 September 2018 08:21:10 EEST Stefan Agner wrote:
> >> Allow to specify the data-enable polarity required by a dumb VGA
> >> DAC converting parallel RGB to VGA.
> >>
> >> Signed-off-by: Stefan Agner <stefan@agner.ch>
> >> ---
> >>
> >> .../devicetree/bindings/display/bridge/dumb-vga-dac.txt | 1 +
> >> 1 file changed, 1 insertion(+)
> >>
> >> diff --git
> >> a/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
> >> b/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt index
> >> 164cbb15f04c..adbd2ca0af2f 100644
> >> --- a/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
> >> +++ b/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
> >> @@ -18,6 +18,7 @@ graph bindings specified in
> >> Documentation/devicetree/bindings/graph.txt.
> >>
> >> Optional properties:
> >> - vdd-supply: Power supply for DAC
> >>
> >> +- de-active: data-enable pulse is active low/high/ignored
> >
> > Which value corresponds to low, high and ignored ?
>
> The wording is taken from
> Documentation/devicetree/bindings/display/panel/display-timing.txt. But
> I agree, not very useful.
>
> 0 is low active, 1 is high active, and none is using driver defaults.
>
> How about:
> - de-active: data-enable pulse is 0=active low/1=active high

The data enable signal isn't really a pulse. I would word this as

- de-active: Polarity of the data enable signal. 0 for active low, 1 for
active high, unset for system-specific defaults.

> >> Example
> >> -------

--
Regards,

Laurent Pinchart