Il 19/02/24 14:59, Michael Walle ha scritto:
On Mon Feb 19, 2024 at 2:35 PM CET, AngeloGioacchino Del Regno wrote:
vbus is always supplied by something, as otherwise USB won't work - whether this
is an always-on regulator or a passthrough from external supply this doesn't really
matter - you should model a regulator-fixed that provides the 5V VBUS line.
I don't think this is correct, though. Think of an on-board USB
hub. There only D+/D- are connected (and maybe the USB3.2 SerDes
lanes). Or have a look at the M.2 pinout. There is no Vbus.
Yes but the MediaTek MTU3 and/or controllers do have it ;-)
.. and ..
For example:
vbus_fixed: regulator-vbus {
compatible = "regulator-fixed";
regulator-name = "usb-vbus";
regulator-always-on;
regulator-boot-on;
regulator-min-microvolt = <5000000>;
regulator-max-microvolt = <5000000>;
};
As mentioned above, I don't think this will make sense in my case.
>> P.S.: If the rail has a different name, please use that different name. Obviously
that requires you to have schematics at hand, and I don't know if you do: if you
don't, then that regulator-vbus name is just fine.
I do have the schematics.
In that case, you should model the power tree with the fixed power lines,
check mt8195-cherry (and/or cherry-tomato) and radxa-nio-12l; even though
those are technically "doing nothing", this is device tree, so it should
provide a description of the hardware ... and the board does have fixed
power lines.
It has at least one: DC-IN (typec, barrel jack or whatever, the board needs
power, doesn't it?!).
Mh, maybe I don't get it. But within the hardware there is simply no
Vbus. Thus I'd argue it doesn't make sense to have a vbus-supply
property. Besides, the mediatek,mtu3.yaml binding lists it as
deprecated anyway and it should rather be on the connector. There,
it makes perfectly sense (at least if it's a USB connector).
Thus in my case, the xhci for the front port has a vbus-supply
property (but it should rather have a connector node, as I've just
learned). But the internal port which connects to the USB hub
shouldn't have one.
+-----+ +-----+ +------+
| |<--Dp/Dn-->| |<------Dp/Dn----->| USB |
| SoC | | | | Conn |
| | | | +-----+ | |
+-----+ | USB | | PWR |--Vbus->| |
| Hub | | SW | +------+
| | +-----+
| | ^
| | | PRTPWR
| |-----'
+-----+
"PWR SW" is a power switch, the input (+5V) isn't shown here. The
power will be enabled by the USB Hub.
Ok then, put the vbus on the connector, where applicable.
If PWR_SW is a physical switch (not detectable), then you can still model it as an
always-on regulator-fixed, as there's no other clean way of doing that.
As for modeling the power tree with the fixed power lines, I mean that you should
add the power rails as described in your schematics.
You will surely have one DC-IN supply, and others. That should be modeled as a
fixed regulator, which outputs to (probably) the PMIC, using it as an input for
its buck regulators.
Again, your PMIC must be getting a voltage from somewhere in order to regulate
that to a different voltage for a different power rail, right? :-)
Regards,
Angelo
