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

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Message-ID: <CAL_Jsq+fV-W+PqZpvns5oFNyGXxKYYrHe1ipG7gj6dN-c2JJ6g@mail.gmail.com>
Date: Fri, 1 Aug 2025 15:22:20 -0500
From: Rob Herring <robh@...nel.org>
To: Miquel Raynal <miquel.raynal@...tlin.com>
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

On Fri, Aug 1, 2025 at 9:27 AM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
>
> 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.

'interrupt-parent' is implicitly allowed anywhere. Who is the parent
is outside the scope of the binding given it can vary.

> > +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.

No one has cared about converting the Marvell bindings, so *shrug*.

Really, the whole example should be deleted when/if the parent is
properly documented.

Rob