On Wed, Apr 27, 2022 at 12:29 PM Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, Apr 21, 2022 at 1:54 PM Maxime Ripard <maxime@xxxxxxxxxx> wrote:
> >
> > On Thu, Apr 21, 2022 at 01:15:54PM +0530, Jagan Teki wrote:
> > > + Linus
> > > + Marek
> > > + Laurent
> > > + Robert
> > >
> > > On Thu, Apr 21, 2022 at 4:40 AM Bjorn Andersson
> > > <bjorn.andersson@xxxxxxxxxx> wrote:
> > > >
> > > > Commit '80253168dbfd ("drm: of: Lookup if child node has panel or
> > > > bridge")' attempted to simplify the case of expressing a simple panel
> > > > under a DSI controller, by assuming that the first non-graph child node
> > > > was a panel or bridge.
> > > >
> > > > Unfortunately for non-trivial cases the first child node might not be a
> > > > panel or bridge. Examples of this can be a aux-bus in the case of
> > > > DisplayPort, or an opp-table represented before the panel node.
> > > >
> > > > In these cases the reverted commit prevents the caller from ever finding
> > > > a reference to the panel.
> > > >
> > > > This reverts commit '80253168dbfd ("drm: of: Lookup if child node has
> > > > panel or bridge")', in favor of using an explicit graph reference to the
> > > > panel in the trivial case as well.
> > >
> > > This eventually breaks many child-based devm_drm_of_get_bridge
> > > switched drivers. Do you have any suggestions on how to proceed to
> > > succeed in those use cases as well?
> >
> > I guess we could create a new helper for those, like
> > devm_drm_of_get_bridge_with_panel, or something.
>
> I think using the same existing helper and updating child support is
> make sense, as there is a possibility to use the same host for child
> and OF-graph bindings.
>
> I can see two possible solutions (as of now)
>
> 1. adding "dcs-child-type" bindings for child-based panel or bridge
> 2. iterate child and skip those nodes other than panel or bridge. or
> iterate sub-child to find it has a panel or bridge-like aux-bus (which
> is indeed hard as this configuration seems not 'standard' i think )
>
> Any inputs?
Checking aux-bus with the sub-node panel can be a possible check to
look at it, any comments?
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -244,6 +244,25 @@ int drm_of_find_panel_or_bridge(const struct
device_node *np,
if (panel)
*panel = NULL;
+ /**
+ * Devices can also be child nodes when we also control that device
+ * through the upstream device (ie, MIPI-DCS for a MIPI-DSI device).
+ *
+ * Lookup for a child node of the given parent that isn't either port
+ * or ports.
+ */
+ for_each_available_child_of_node(np, remote) {
+ if (of_node_name_eq(remote, "port") ||
+ of_node_name_eq(remote, "ports"))
+ continue;
+
+ if (!(of_node_name_eq(remote, "aux-bus") &&
+ of_get_child_by_name(remote, "panel")))
+ continue;
+
+ goto of_find_panel_or_bridge;
+ }
+
/*
* of_graph_get_remote_node() produces a noisy error message if port
* node isn't found and the absence of the port is a legit case here,
@@ -254,6 +273,8 @@ int drm_of_find_panel_or_bridge(const struct
device_node *np,
return -ENODEV;
remote = of_graph_get_remote_node(np, port, endpoint);
+
+of_find_panel_or_bridge:
if (!remote)
return -ENODEV;
Jagan.
