[PATCH] dt-bindings: usb: snps,dwc3-common: Document usb-psy-name

[PATCH] dt-bindings: usb: snps,dwc3-common: Document usb-psy-name

[Venkat Yadlapati via B4 Relay]

From: Venkat Yadlapati <venkat.yadlapati@yahoo.com>

The dwc3 driver reads usb-psy-name since commit 6f0764b5adea ("usb: dwc3:
add a power supply for current control") to tell a power supply the
current the USB host grants, but the property was never documented.

An LLM was used to help write this commit message.

Signed-off-by: Venkat Yadlapati <venkat.yadlapati@yahoo.com>
---
The dwc3 driver has read usb-psy-name for a long time, but the property
was never documented. The Motorola Signature uses it to tell the
qcom_battmgr USB power supply the current the host grants.

Checked with dt_binding_check and with dtbs_check on the Motorola
Signature devicetree, which sets the property.

I used an LLM (Claude) to help write this patch and its commit message.
I reviewed it.
---
 Documentation/devicetree/bindings/usb/snps,dwc3-common.yaml | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/devicetree/bindings/usb/snps,dwc3-common.yaml b/Documentation/devicetree/bindings/usb/snps,dwc3-common.yaml
index 6c0b8b653824..5d46db402f93 100644
--- a/Documentation/devicetree/bindings/usb/snps,dwc3-common.yaml
+++ b/Documentation/devicetree/bindings/usb/snps,dwc3-common.yaml
@@ -42,6 +42,13 @@ properties:
     minItems: 1
     maxItems: 19
 
+  usb-psy-name:
+    $ref: /schemas/types.yaml#/definitions/string
+    description:
+      Name of the power supply that is told the current the USB host
+      grants to the device (e.g. after enumeration), so the charger can
+      draw it.
+
   phy-names:
     minItems: 1
     maxItems: 19

---
base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
change-id: 20261116-vantage-dwc3-eccc2f123d3c

Best regards,
--  
Venkat Yadlapati <venkat.yadlapati@yahoo.com>

Re: [PATCH] dt-bindings: usb: snps,dwc3-common: Document usb-psy-name

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] dt-bindings: usb: snps,dwc3-common: usb-psy-name exposes
  Linux psy name
--

commit 4bb8a88bbaa8fbc9c3b1e6963f4478fd21569377
Author: Venkat Yadlapati <venkat.yadlapati@yahoo.com>

dt-bindings: usb: snps,dwc3-common: Document usb-psy-name

This commit documents the usb-psy-name string property in the common
Synopsys DWC3 Devicetree binding schema.

> diff --git a/Documentation/devicetree/bindings/usb/snps,dwc3-common.yaml b/Documentation/devicetree/bindings/usb/snps,dwc3-common.yaml
> index 6c0b8b6538246..5d46db402f935 100644
> --- a/Documentation/devicetree/bindings/usb/snps,dwc3-common.yaml
> +++ b/Documentation/devicetree/bindings/usb/snps,dwc3-common.yaml
> @@ -42,6 +42,13 @@ properties:
>      minItems: 1
>      maxItems: 19
>  
> +  usb-psy-name:
> +    $ref: /schemas/types.yaml#/definitions/string
> +    description:
> +      Name of the power supply that is told the current the USB host
> +      grants to the device (e.g. after enumeration), so the charger can
> +      draw it.
> +
>    phy-names:
>      minItems: 1
>      maxItems: 19

[Severity: Medium]
Should usb-psy-name be part of the Devicetree binding ABI rather than a
phandle reference?

In drivers/usb/dwc3/core.c, dwc3_get_usb_power_supply() passes
usb-psy-name to power_supply_get_by_name(), which matches against the
Linux-internal power_supply_desc.name string (such as "qcom-battmgr-usb").
Devicetree bindings describe hardware relationships between devices using
phandles (for example, power-supplies or a usb-connector graph link)
rather than Linux driver registration names, which are normally only used
by legacy board files or software_node glue.

In addition, the qcom_battmgr use case mentioned in the patch notes will
not work at runtime: dwc3_vbus_draw_work() calls
power_supply_set_property() with POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT,
but neither sm8350_usb_psy_desc nor sc8280xp_usb_psy_desc in
drivers/power/supply/qcom_battmgr.c defines a .set_property callback, so
power_supply_set_property() always returns -ENODEV.

Also, this places usb-psy-name in the middle of the paired phys and
phy-names properties.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261116-vantage-dwc3-v1-1-6abb5a3277f0@yahoo.com?part=1