[RFC 2/3] drm/panel: Add simple panel support

Thierry Reding thierry.reding at gmail.com
Wed Sep 4 07:38:30 PDT 2013

On Tue, Sep 03, 2013 at 12:52:36PM -0600, Stephen Warren wrote:
> On 08/30/2013 09:25 AM, Thierry Reding wrote:
> > Add a driver for simple panels. Such panels can have a regulator that
> > provides the supply voltage and a separate GPIO to enable the panel.
> > Optionally the panels can have a backlight associated with them so it
> > can be enabled or disabled according to the panel's power management
> > mode.
> > diff --git a/Documentation/devicetree/bindings/panel/panel-simple.txt b/Documentation/devicetree/bindings/panel/panel-simple.txt
> > +Simple display panel
> > +
> > +Required properties:
> > +- compatible: should be one of:
> > +  - "auo,b101aw03": AU Optronics Corporation 10.1" WSVGA TFT LCD panel
> > +  - "cptt,claa101wb03": Chunghwa Picture Tubes Ltd. 10.1" WXGA TFT LCD panel
> > +  - "pc,vvx10f004b00": Panasonic Corporation 10.1" WUXGA TFT LCD panel
> > +
> > +Optional properties:
> > +- ddc-i2c-bus: phandle of an I2C controller used for DDC EDID probing
> > +- power-supply: regulator to provide the supply voltage
> > +- enable-gpios: GPIO pin to enable or disable the panel
> > +- backlight: phandle of the backlight device attached to the panel
> Do we need to represent the timing requirements e.g. between panel
> enable and backlight enable, or do you expect the driver to hard-code
> this based on the compatible value?

Yes, I'd expect the driver to hard-code that, similar to how the video
mode is hardcoded. ddc-i2c-bus support hasn't even been implemented yet.
I was planning to do that because one of the panels (the Chunghwa I
think) actually is connected via DDC. What I was going to do was prefer
a hardcoded mode over EDID to allow a driver to override a faulty EDID.

> Looking at the driver code, it seems that it has direct knowledge of the
> video mode that each panel supports, so DDC is actually optional unlike
> what I asserted/assumed in my previous response. As such, I guess we
> should have a separate DT binding document for each of the three panels
> (compatible values) listed above that pretty much just says "go look at
> simple-panel.txt".

Okay, I suppose that makes sense.

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