On Mon, Jun 7, 2021 at 7:06 PM Douglas Anderson dianders@chromium.org wrote:
We want to be able to list an eDP panel as a child of an eDP controller node to represent the fact that the panel is connected to the controller's DP AUX bus. Though the panel and the controller are connected in several ways, the DP AUX bus is the primary control interface between the two and thus makes the most sense to model in device tree hierarchy.
Listing a panel in this way makes it possible for the panel driver to easily get access to the DP AUX bus that it resides on, which can be useful to help in auto-detecting the panel and for turning on various bits.
NOTE: historically eDP panels were _not_ listed under their controller but were listed at the top level of the device tree. This will still be supported for backward compatibility (and while DP controller drivers are adapted to support the new DT syntax) but should be considered deprecated since there is no downside to listing the panel under the controller.
For now, the DP AUX bus bindings will only support an eDP panel underneath. It's possible it could be extended to allow having a DP connector under it in the future.
NOTE: there is no "Example" in this bindings file. Yikes! This avoids duplicating the same example lots of places. See users of the aux bus (like ti-sn65dsi86) for examples.
The idea for this bus's design was hashed out over IRC [1].
[1] https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&date=2...
Signed-off-by: Douglas Anderson dianders@chromium.org Reviewed-by: Rob Herring robh@kernel.org
I overall like this approach a lot: Reviewed-by: Linus Walleij linus.walleij@linaro.org
Yours, Linus Walleij