Quoting Dmitry Baryshkov (2024-10-25 03:49:36)
> On Tue, Oct 22, 2024 at 06:15:47PM -0700, Stephen Boyd wrote:
> > Quoting Dmitry Baryshkov (2024-09-20 02:38:53)
> > > On Sat, Aug 31, 2024 at 09:06:53PM GMT, Stephen Boyd wrote:
>
> >
> > Either way the problem seems to be that I need to associate one
> > drm_bridge with two displayport altmode drivers and pass some fwnode
> > handle to drm_connector_oob_hotplug_event() in a way that we can map
> > that back to the right output endpoint in the DP bridge graph. That
> > seems to imply that we need to pass the fwnode for the usb-c-connector
> > in addition to the fwnode for the drm_bridge, so that the drm_bridge
> > code can look at its DT graph and find the remote node connected.
> > Basically something like this:
> >
> > void drm_connector_oob_hotplug_event(struct fwnode_handle *connector_fwnode,
> > struct fwnode_handle
> > *usb_connector_fwnode,
> > enum drm_connector_status status)
> >
> > (We might as well also pass the number of lanes here)
>
> I think this is a bit of an overkill.
>
> The drm_connector_oob_hotplug_event() is fine as it is, it gets
> "fwnode_handle to report the event on".
Ok. I understand that drm_*() shouldn't know about USB or type-c in
general.
>
> What needs to be changed (in my humble opinion) is the
> drm_connector_find_by_fwnode() function (or likely a new function is to
> be added): if it can not find drm_connector for the passed fwnode, it
> should look it up on the parent, then on parent's parent, etc, until we
> actually find the drm_connector (good) or we reach the root (sad).
>
> And finally after getting the drm_connector, the oob_hotplug_event()
> callback should also receive the fwnode argument. This way the connector
> (or the bridge) can identify the fwnode (aka usb-c-connector in our
> case) that caused the event.
>
> WDYT?
Ok I think I'm following along. The dp->connector_fwnode in
displayport.c will always be the usb-c-connector node in your example?
And that will search for the connector or bridge associated with that
usb-c-connector node. Then when it comes time to call
drm_connector_oob_hotplug_event() it will take the usb-c-connector
fwnode as 'connector_fwnode' and in that function we'll make
drm_connector_find_by_fwnode() implement the parent walk? The
cros-ec-typec compatible node will register a drm_bridge in all cases,
and that is the parent of the usb-c-connector node, so the walk will end
there.
Then you want to pass the usb-c-connector fwnode to
connector->funcs->oob_hotplug_event()? So
drm_bridge_connector_oob_hotplug_event() changes to also get the
usb-c-connector fwnode. This plan should work.
At this point we need to tell the DP bridge, like IT6505, that it's one
or the other output endpoints that it should use, but we haven't
directly connected the usb-c-connector to the output ports of IT6505
because drm_of_find_panel_or_bridge() can't find the parent of the
usb-c-connector if we connect the DP bridge to the usb-c-connector
graphs. We'll need a way for the bridge to know which output port is
connected to a usb-c-connector fwnode. Some sort of API like
fwnode_graph_get_endpoint_connected_to_fwnode(bridge_fwnode, usb_c_fwnode)
that takes the bridge fwnode and traverses the graph to find the
endpoint in that's connected to 'usb_c_fwnode'. That traversal API will
need help from the intermediate node, cros-ec-typec, so maybe it is
better as a drm_bridge API that uses some new drm_bridge_funcs callback.
This way IT6505 can ask the bridge chain which output DP endpoint is
actually associated with the connector fwnode it gets from the
oob_hotplug_event() callback.
Here's the two DT snippets that I've ended up with:
typec {
compatible = "google,cros-ec-typec";
ports {
port@0 {
reg = <0>;
typec_dp_in: endpoint {
remote-endpoint = <&usb_1_qmp_phy_out_dp>;
};
};
port@1 {
reg = <1>;
typec_usb0_in: endpoint@0 {
reg = <0>;
remote-endpoint = <&usb_hub_dfp1_ss>;
};
typec_usb1_in: endpoint@1 {
reg = <1>;
remote-endpoint = <&usb_hub_dfp2_ss>;
};
}
// This port is not really needed because we know the
// mapping from input ports to usb-c-connectors
port@2 {
reg = <2>;
typec0_out: endpoint@0 {
reg = <0>;
remote-endpoint = <&usb_c0_ss_in>;
};
typec1_out: endpoint@1 {
reg = <1>;
remote-endpoint = <&usb_c1_ss_in>;
};
}
};
usb_c0: connector@0 {
compatible = "usb-c-connector";
reg = <0>;
ports {
port@0 {
reg = <0>;
usb_c0_hs_in: endpoint {
remote-endpoint = <&usb_hub_dfp1_hs>;
};
};
port@1 {
reg = <1>;
usb_c0_ss_in: endpoint {
remote-endpoint = <&typec0_out>;
};
};
};
};
usb_c1: connector@1 {
compatible = "usb-c-connector";
reg = <1>;
ports {
port@0 {
reg = <0>;
usb_c1_hs_in: endpoint {
remote-endpoint = <&usb_hub_dfp2_hs>;
};
};
port@1 {
reg = <1>;
usb_c1_ss_in: endpoint {
remote-endpoint = <&typec1_out>;
};
};
};
};
};
&usb_1_qmpphy {
ports {
port@0 {
endpoint@0 {
data-lanes = <0 1>;
// this might go to USB-3 hub
};
usb_1_qmp_phy_out_dp: endpoint@1 {
remote-endpoint = <&typec_dp_in>;
data-lanes = <2 3>;
};
}
};
};
-------
typec {
ports {
port@0 {
reg = <0>;
typec_dp0_in: endpoint@0 {
reg = <0>;
remote-endpoint = <&dp_bridge_out_0>;
};
typec_dp1_in: endpoint@1 {
reg = <1>;
remote-endpoint = <&dp_bridge_out_1>;
};
};
port@1 {
reg = <1>;
typec_usb0_in: endpoint@0 {
reg = <0>;
remote-endpoint = <&usb_hub_0_ss>;
};
typec_usb1_in: endpoint@1 {
reg = <1>;
remote-endpoint = <&usb_hub_1_ss>;
};
}
};
connector@0 {
port@1 {
endpoint@0 {
remote-endpoint = <&usb_hub_0_hs>;
};
};
};
connector@1 {
port@1 {
endpoint@0 {
remote-endpoint = <&usb_hub_1_hs>;
};
};
};
};
dp_bridge {
ports {
port@1 {
dp_bridge_out_0: endpoint@0 {
remote-endpoint = <&typec_dp0_in>;
data-lanes = <0 1>;
};
dp_bridge_out_1: endpoint@1 {
remote-endpoint = <&typec_dp1_in>;
data-lanes = <2 3>;
};
};
};
};
-------
I wonder about a case where we may take two lanes and connect them to a
usb-c-connector and then take the other two lanes and send them through
a mux to two more usb-c-connectors. I think we'll need another property
in that case that indicates which input DP endpoints correspond to the
usb-c-connector nodes.
typec {
ports {
port@0 {
reg = <0>;
typec_dp0_in: endpoint@0 {
reg = <0>;
remote-endpoint = <&dp_bridge_out_0>;
};
typec_dp1_in: endpoint@1 {
reg = <1>;
remote-endpoint = <&dp_bridge_out_1>;
};
};
port@1 {
reg = <1>;
typec_usb0_in: endpoint@0 {
reg = <0>;
remote-endpoint = <&usb_hub_0_ss>;
};
typec_usb1_in: endpoint@1 {
reg = <1>;
remote-endpoint = <&usb_hub_1_ss>;
};
typec_usb2_in: endpoint@2 {
reg = <2>;
remote-endpoint = <&usb_hub_2_ss>;
};
}
};
dp-2-usb-mapping = <0 0>, <1 1>, <1 2>;
};
This property would indicate dp endpoint 0 goes to usb-c-connector 0
while dp endpoint 1 goes to usb-c-connector 1 and 2. I don't have this
hardware but I could see how someone might do this by adding another mux
that the EC controls. I don't want to design a binding and have to
rework it in the future to handle this new case. I hope adding a new
property, or getting more information from the EC firmware, will be
sufficient to describe the linkage between the DP endpoint and the
connectors managed by the cros-ec-typec device.
>
> > Corsola could work with this design, but we'll need to teach
> > dp_altmode_probe() to look for the drm_bridge elsewhere besides as the
> > parent of the usb-c-connector node. That implies using the 'displayport'
> > property in the cros-ec-typec node or teaching dp_altmode_probe() to
> > look for the port@1/endpoint@1 remote-endpoint handle in the
> > usb-c-connector graph.
> >
> > Assuming the bindings you've presented here are fine and good and I got
> > over the differences between Trogdor and Corsola, then I can make mostly
> > everything work with the drm_connector_oob_hotplug_event() signature
> > change from above and some tweaks to dp_altmode_probe() to look for
> > port@1/endpoint@1 first because that's the "logical" DP input endpoint
> > in the usb-c-connector binding's graph. Great! The final roadblock I'm
> > at is that HPD doesn't work on Trogdor, so I can't signal HPD through
> > the typec framework.
>
> Hmm, I thought that a normal DP's HPD GPIO works on the trogdor. Was I
> misunderstanding it? But then we don't know, which USB-C connector
> triggered the HPD...
By HPD not working on Trogdor I mean that the EC doesn't tell the kernel
about the state of HPD for a usb-c-connector in software. Instead, HPD
is signaled directly to the DP controller in hardware via a GPIO. It is
as you suspect, we don't know which USB-C connector has HPD unless we
read the mux controlled by the EC and combine that with what the DP
driver knows about the state of the HPD pin.
>
> > This series fixes that problem by "capturing" HPD state from the
> > upstream drm_bridge, e.g. msm_dp, by hooking the struct
> > drm_bridge_funcs::hpd_notify() path and injecting HPD into the typec
> > messages received from the EC. That's a workaround to make the typec
> > framework see HPD state changes that are otherwise invisible to the
> > kernel. Newer firmwares actually tell us the state of HPD properly, but
> > even then we have to read a gpio mux controlled by the EC to figure out
> > which usb-c-connector is actually muxing DP when HPD changes on either
> > typec_port. Having a drm_bridge in cros-ec-typec helped here because we
> > could hook this path and signal HPD if we knew the firmware was fixed.
> > If we don't have the drm_bridge anymore, I'm lost how to do this.
>
> It's probably okay to add one, but let me think if we can work without
> it. Can we make EC driver listen for that single HPD GPIO (by making it
> an actual GPIO rather than "dp_hot") and then react to it?
I don't know how we handle the attention message, HPD_IRQ, because
that's a short pulse that the kernel may miss when this is a GPIO that
has to be triggered when both falling and rising. When the pin goes
directly to the DP controller this is fine because the hardware can
detect that. Similarly, when the EC sends the message about an HPD_IRQ
we can replay that into the type-c framework and signal attention
through drm_connector_oob_hotplug_event()/hpd_notify() paths.
>
> >
> > Maybe the right answer here is to introduce a drm_connector_dp_typec
> > structure that is created by the TCPM (cros-ec-typec) that sets a new
> > DRM_BRIDGE_OP_DP_TYPEC bridge op flag? And then teach
> > drm_bridge_connector about this new flag, similar to the HDMI one. The
> > drm_bridge could implement some function that maps the typec_port
> > (usb-c-connector) to the upstream drm_bridge (ANX7625) graph port,
> > possibly all in drm_bridge_connector_oob_hotplug_event() so that nothing
> > else really changes. It could also let us keep hooking the hpd_notify()
> > path for the workaround needed on Trogdor. And finally it may let us
> > harmonize the two DT bindings so that we only have one port@1/endpoint
> > node in the usb-c-connector.
>
> I think we have lightly discussed adding drm_connector_displayport, so
> that part is okay. But my gut feeling is that there should be no _typec
> part in thart picture. The DRM framework shouldn't need to know all the
> Type-C details.
>
Alright, got it.
