linux-kernel - Re: [PATCH] dt-binding: thermal: Convert marvell,armada-ap806-thermal to DT schema

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Message-ID: <87qzxv5d7z.fsf@bootlin.com>
Date: Fri, 01 Aug 2025 16:27:28 +0200
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: "Rob Herring (Arm)" <robh@...nel.org>
Cc: Andrew Lunn <andrew@...n.ch>,  Gregory Clement
 <gregory.clement@...tlin.com>,  Sebastian Hesselbarth
 <sebastian.hesselbarth@...il.com>,  Krzysztof Kozlowski
 <krzk+dt@...nel.org>,  Conor Dooley <conor+dt@...nel.org>,  "Rafael J.
 Wysocki" <rafael@...nel.org>,  Daniel Lezcano <daniel.lezcano@...aro.org>,
  Zhang Rui <rui.zhang@...el.com>,  Lukasz Luba <lukasz.luba@....com>,
  linux-arm-kernel@...ts.infradead.org,  devicetree@...r.kernel.org,
  linux-kernel@...r.kernel.org,  linux-pm@...r.kernel.org, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH] dt-binding: thermal: Convert
 marvell,armada-ap806-thermal to DT schema

Hi Rob,

Sorry for the delay, I don't know why I forgot these.

...

> +properties:
> +  compatible:
> +    enum:
> +      - marvell,armada-ap806-thermal
> +      - marvell,armada-ap807-thermal
> +      - marvell,armada-cp110-thermal
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    description: overheat interrupt
> +    maxItems: 1
> +
> +  '#thermal-sensor-cells':
> +    description: Cell represents the channel ID. There is one sensor per
> +      channel. O refers to the thermal IP internal channel.
> +    const: 1
> +
> +required:
> +  - compatible
> +  - reg
> +
> +additionalProperties: false

IIRC on these Marvell designs, there was one (or more, I don't remember)
Application Processor (AP) and several Co-Processors (CP).

[On the AP]
The AP8XX overheat interrupt was not directly wired to the GIC but was
going through another intermediate IRQ controller named SEI (System
Error Interrupt).

      Thermal overheat IRQ -> SEI -> GIC

[On the CP]
There was one interrupt controller per CP11X named ICU, which would be
connected to the top level GIC through MSIs. The ICU was however split
into several sub-controllers reaching different areas on the GIC.

                                      MSI
      Thermal overheat IRQ -> ICU SEI -> GIC

As the OS could not guess the internal connexions, I believe we had to
include in the bindings the parent IRQ chip we were connected to. In the
case of the thermal over heat interrupts, they were all going through an
SEI controller (System Error Interrupt) which, if I still remember
correctly, was not the default parent, hence the use of
interrupts-parent/interrupts-extended in the examples.

This is all a bit cloudy in my mind, but I believe these properties
matter and with 'additionalProperties: false' and without
interrupts-parent/interrupts-extended allowed, a real world DT
snippet would not pass the binding checks.

> +examples:
> +  - |
> +    thermal-sensor@80 {
> +        compatible = "marvell,armada-ap806-thermal";
> +        reg = <0x80 0x10>;
> +        interrupts = <18>;

I do not know how accurate the example must be, but maybe the example
shall reflect the SEI connection as well.

> +        #thermal-sensor-cells = <1>;
> +    };

Thanks,
Miquèl