Hi John,
Am Montag, den 22.02.2016, 14:14 +0000 schrieb John Keeping:
> Hi,
>
> Is there a reason why endpoints in a device tree graph can't be
> disabled?
You can always remove them using /delete-node/, which also has the
advantage of reminding you not to leave a single dangling endpoint.
> I would like to be able to force the use of a particular CRTC for
> certain outputs even though the hardware is capable of connecting any
> CRTC to any output. In this case I need to be able to support a wide
> range of frequencies for external HDMI monitors so I will configure one
> of the CRTCs to be able to generate these while the other will be tied
> into a limited set of clock rates as a result of the overall system
> clock setup.
>
> Currently this can only be achieved by removing the endpoints from the
> base SoC .dtsi file but it feels like it should be possible to add
> 'status = "disabled"' to the nodes in the board-specific .dts in order
> to disable undesirable configurations.
>
> I tested the change below and it behaves exactly as I want, but I don't
> claim to understand all of the users of these functions to know if it
> will break something else (hence this isn't a formal patch).
I don't know that any driver depends on being able to parse disabled
endpoints, but given the above I'm not sure that keeping disabled
endpoints in the device tree is a useful feature.
Disabling ports makes more sense to me. It should be documented in
Documentation/devicetree/bindings/graph.txt though.
> -- >8 --
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 017dd94..1e56b91 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -2143,7 +2143,7 @@ struct device_node *of_graph_get_port_by_id(struct device_node *parent, u32 id)
> if (node)
> parent = node;
>
> - for_each_child_of_node(parent, port) {
> + for_each_available_child_of_node(parent, port) {
> u32 port_id = 0;
>
> if (of_node_cmp(port->name, "port") != 0)
> @@ -2209,7 +2209,7 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
> * getting the next child. If the previous endpoint is NULL this
> * will return the first child.
> */
> - endpoint = of_get_next_child(port, prev);
> + endpoint = of_get_next_available_child(port, prev);
> if (endpoint) {
> of_node_put(port);
> return endpoint;
> @@ -2219,7 +2219,7 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
> prev = NULL;
>
> do {
> - port = of_get_next_child(parent, port);
> + port = of_get_next_available_child(parent, port);
> if (!port)
> return NULL;
> } while (of_node_cmp(port->name, "port"));
> -- 8< --
>
>
> Thanks,
> John
best regards
Philipp
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