[PATCH] of: Add simple panel device tree binding

[Tomi Valkeinen]

On 2013-11-22 20:41, Thierry Reding wrote:

> +Example:
> +
> +	panel: panel {
> +		compatible = "cptt,claa101wb01";
> +		ddc-i2c-bus = <&panelddc>;
> +
> +		power-supply = <&vdd_pnl_reg>;
> +		enable-gpios = <&gpio 90 0>;
> +
> +		backlight = <&backlight>;
> +	};

I'm somewhat torn with this, as I agree with Thierry that it's correct
to have a panel database in the driver, but, on the other hand, it does
seem impractical.

In my experience, there are lots of panels out there, and each board I
have has a different one. So, while just a gut feeling, we could end up
with lots of panel, each used only on one board.

With a quick thought, things would work fine if we just added the
videomode data to the DT data, instead of a driver database, as Laurent
suggested.

However... I don't think the panels are usually as simple as that. With
the panels I've worked with, the driver has to know things like:

- Does the power supply need to be enabled before the enable gpio, and
if so, how long before? And the same for power off.

- Does the video stream need to be enabled before the enable gpio, and
if so, how long before? And the same for power off.

- Is the gpio enable, power down, or reset? If reset, what are the timings.

Where will those be defined? This goes back to the power sequence stuff
again... (Was the power sequences series forgotten?) And defining such
sequences in DT data is, I think, bad idea. But having them in the
driver would be fine. If we have those in the driver, it's better to
have the video modes there also.

The sequence for power, gpio and video stream is most likely common for
most panels. Power-on is done with enabling, in order: power, video,
gpio. And power-off is vice versa. But we need delays in between, and I
don't know if we can have some kind of common delays that'd work for
most of the panels.

If we can, we could perhaps define in detail our "common simple panel"
spec, which would contain sequences, timings, powers, gpios, and so on,
so it would be easy to see if a particular panel fits into our simple
panel spec.

 Tomi


-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 901 bytes
Desc: OpenPGP digital signature
URL: <http://lists.freedesktop.org/archives/dri-devel/attachments/20131211/9ce0e72b/attachment.pgp>