regulator: support the HiSilicon STB PMOC voltage rails

[Severity: Medium]
Will this strict constraint reject device trees for the other supported SoCs?

The description explicitly mentions support for multiple HiSilicon STB SoCs (Hi3798cv200/mv100/mv200) which have different voltage reference designs. However, restricting the compatible property to a single exact value (hisilicon,hi3798cv200-regulator) rejects device trees that use SoC-specific compatible strings (e.g., hisilicon,hi3798mv200-regulator) or fallback lists.

This prevents the proper representation of the other supported hardware variants without failing schema validation (dt_binding_check).

[Severity: High]
Does the lack of hardware calibration properties here cause overvoltage in the driver?

By not including properties to describe the physical hardware bounds (e.g., duty-cycle mappings or pwm-regulator integration), strict validation prevents defining these board-specific calibration values in the device tree.

As a result, the follow-up commit "regulator: histb: add voltage regulator driver" relies on the standard OS policy constraints (regulator-min-microvolt and regulator-max-microvolt) as physical 100% and 0% duty cycle calibration boundaries:

drivers/regulator/histb-regulator.c:histb_regulator_probe() {
    ...
        priv->min_uV = init_data->constraints.min_uV;
        priv->max_uV = init_data->constraints.max_uV;
    ...
}

If a device tree author specifies a tighter policy constraint to protect hardware (e.g., a maximum of 1.0V when the physical maximum is 1.15V), a legitimate request for 1.0V outputs a 0% duty cycle:

drivers/regulator/histb-regulator.c:histb_regulator_set_voltage() {
    ...
        if (min_uV >= priv->max_uV)
                duty = 0;
    ...
}

This configures the hardware to physically deliver the unconstrained maximum of 1.15V, completely bypassing the intended safety bounds and potentially damaging connected components.

The PMOC block of the HiSilicon STB SoCs (Hi3798cv200/mv100/mv200) drives an external converter with a PWM signal. Add dt-binding doc.

Signed-off-by David Yang <[email protected]>

---
 .../hisilicon,hi3798cv200-regulator.yaml      | 48 +++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml new file +4 -0

new file mode 100644
index 000000000000..812d94aca1f5
@@ -0,0 +1,48 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/hisilicon,hi3798cv200-regulator.yaml#

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml new file +17 -0

+
+  The voltage range depends on the board design: reference designs specify
+  0.65 V to 1.15 V for the Hi3798cv200, and 0.7 V to 1.25 V for the Hi3798mv200;
+  a customized board has to figure out its own. The regulator itself has no
+  other source of calibration.
+
+properties:
+  compatible:
+    const: hisilicon,hi3798cv200-regulator
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - regulator-min-microvolt

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml line 14

Quoted 3 lines · David Yang

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml new file +3 -0

+description: |
+  HiSilicon STB SoCs (Hi3798cv200/mv100/mv200) provide PWM outputs in the PMOC
+  block which drive an external converter.

SoCs rarely provide supplies for themselves (they are rather called power domains in such case) and above wording suggests this is actually something external. It also speaks about PWM but binding has no PWM.

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml line 43

Quoted 2 lines

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml new file +2 -0

+        compatible = "hisilicon,hi3798cv200-regulator";
+        reg = <0x8a23018 0x4>;

And one word is rarely a device, which adds to the confusion.

Quoted 9 lines · Krzysztof Kozlowski

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml line 14

Quoted 3 lines · David Yang

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml new file +3 -0

+description: |
+  HiSilicon STB SoCs (Hi3798cv200/mv100/mv200) provide PWM outputs in the PMOC
+  block which drive an external converter.

SoCs rarely provide supplies for themselves (they are rather called power domains in such case) and above wording suggests this is actually something external. It also speaks about PWM but binding has no PWM.

I think this is talking about something like pwm-regulator.c.

Quoted 4 lines

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml line 43

Quoted 2 lines

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml new file +2 -0

+        compatible = "hisilicon,hi3798cv200-regulator";
+        reg = <0x8a23018 0x4>;

And one word is rarely a device, which adds to the confusion.

It is possible for a simple analog block...

Quoted 7 lines

Quoted 5 lines

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml line 43

Quoted 3 lines

Documentation/devicetree/bindings/regulator/hisilicon,hi3798cv200-regulator.yaml new file +2 -0

+        compatible = "hisilicon,hi3798cv200-regulator";
+        reg = <0x8a23018 0x4>;

And one word is rarely a device, which adds to the confusion.

It is possible for a simple analog block...

Hi, I'm planning to spin up with another version. What should I do with the binding next?