Hi Paul,
On Thu, Mar 03, 2022 at 09:26:30PM +0100, Paul Kocialkowski wrote:
> On Wed 02 Feb 22, 21:34, Jagan Teki wrote:
> > Devices can also be child nodes when we also control that device
> > through the upstream device (ie, MIPI-DCS for a MIPI-DSI device).
> >
> > drm_of_find_panel_or_bridge can lookup panel or bridge for a given
> > device has port and endpoint and it fails to lookup if the device
> > has a child nodes.
>
> This patch breaks the logicvc drm driver that I'm currently developping.
> The symptom is that drm_of_find_panel_or_bridge now always returns
> -EPROBE_DEFER even after the panel has probed and is running well.
> It seems that the function can no longer find the panel.
>
> I haven't figured out the details, but reverting your patch makes
> it work again. I suspect other drivers might be affected as well, so
> it would probably be a good idea to revert the patch until the root
> cause is clearly understood and the patch can be adapted accordingly.
>
> Here is what the device-tree looks like:
>
> / {
> panel: panel-lvds {
> compatible = "panel-lvds";
>
> [...]
>
> port {
> #address-cells = <1>;
> #size-cells = <0>;
>
> panel_input: endpoint@0 {
> reg = <0>;
> remote-endpoint = <&logicvc_output>;
> };
> };
> };
> };
>
> &amba {
> logicvc: logicvc@43c00000 {
> compatible = "xylon,logicvc-3.02.a", "syscon", "simple-mfd";
> reg = <0x43c00000 0x6000>;
>
> #address-cells = <1>;
> #size-cells = <1>;
>
> [...]
>
> logicvc_display: display-engine@0 {
> compatible = "xylon,logicvc-4.01.a-display";
>
> [...]
I think the issue lies in what you left out here: you have another node
aside from the port one, called layers. I *think* the issue is that the
code will now pick up the layers node, and try to use it as a panel,
which will never probe.
I've had a look at all the other bindings though, it seems like this
driver is the only one that can be affected: the anx7625 seems to be the
only other driver that has a child node that isn't either a port or a
panel (aux-bus) but it doesn't use drm_of_find_panel_or_bridge either.
Maxime
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