[PATCH V2 2/4] drm/bridge: Introduce pre_enable_upstream_first to alter bridge init order

[Jagan Teki]

Hi Dave,

On Fri, Mar 4, 2022 at 8:48 PM Dave Stevenson
<dave.stevenson at raspberrypi.com> wrote:
>
> DSI sink devices typically want the DSI host powered up and configured
> before they are powered up. pre_enable is the place this would normally
> happen, but they are called in reverse order from panel/connector towards
> the encoder, which is the "wrong" order.
>
> Add a new flag pre_enable_upstream_first that any bridge can set
> to swap the order of pre_enable (and post_disable) for that and the
> immediately upstream bridge.
> Should the immediately upstream bridge also set the
> pre_enable_upstream_first flag, the bridge upstream of that will be called
> before either of those which requested pre_enable_upstream_first.
>
> eg:
> - Panel
> - Bridge 1
> - Bridge 2 pre_enable_upstream_first
> - Bridge 3
> - Bridge 4 pre_enable_upstream_first
> - Bridge 5 pre_enable_upstream_first
> - Bridge 6
> - Encoder
> Would result in pre_enable's being called as Panel, Bridge 1, Bridge 3,
> Bridge 2, Bridge 6, Bridge 5, Bridge 4, Encoder.

Look like this is something that I've reproduced before, isn't it?
https://patchwork.kernel.org/project/dri-devel/patch/20210214194102.126146-6-jagan@amarulasolutions.com/

Jagan.