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);@@ -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;-- 8< --
Thanks, John
best regards Philipp