linux-kernel - Re: [PATCH 1/3] dt-bindings: reset: syscon-reboot: Add priority property

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Date:   Fri, 2 Sep 2022 15:37:21 -0500
From:   Rob Herring <robh@...nel.org>
To:     Pali Rohár <pali@...nel.org>
Cc:     Marek Behún <kabel@...nel.org>,
        devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 1/3] dt-bindings: reset: syscon-reboot: Add priority
 property

On Mon, Aug 22, 2022 at 03:50:50PM +0200, Pali Rohár wrote:
> On Monday 22 August 2022 07:47:28 Rob Herring wrote:
> > On Sat, Aug 20, 2022 at 12:29:23PM +0200, Pali Rohár wrote:
> > > This new optional priority property allows to specify custom priority level
> > > of reset device. Default level was always 192.
> > 
> > Why do we need/want this? What problem does it solve?
> 
> See patch 3/3.
> 
> > > Signed-off-by: Pali Rohár <pali@...nel.org>
> > > ---
> > >  .../devicetree/bindings/power/reset/syscon-reboot.yaml        | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/power/reset/syscon-reboot.yaml b/Documentation/devicetree/bindings/power/reset/syscon-reboot.yaml
> > > index da2509724812..d905133aab27 100644
> > > --- a/Documentation/devicetree/bindings/power/reset/syscon-reboot.yaml
> > > +++ b/Documentation/devicetree/bindings/power/reset/syscon-reboot.yaml
> > > @@ -42,6 +42,10 @@ properties:
> > >      $ref: /schemas/types.yaml#/definitions/uint32
> > >      description: The reset value written to the reboot register (32 bit access).
> > >  
> > > +  priority:
> > 
> > A bit too generic for the name.
> > 
> > > +    $ref: /schemas/types.yaml#/definitions/sint32
> > > +    description: Priority level of this syscon reset device. Default 192.
> > 
> > default: 192
> > 
> > 
> > Though I'm not really sure about the whole concept of this in DT. Where 
> > does 192 come from?
> 
> Implicitly from the current implementation and how it is used.

Implementation of what? u-boot? BSD? robOS?

> > Presumably if we have more than 1 reset device, then 
> > 'priority' is needed in multiple places. So you need a common schema 
> > defining the property (as property types should be defined exactly 
> > once) which this schema can reference.
> > 
> > Rob
> 
> Sorry, I do not understand.

So just keep sending new versions instead?

syscon-reboot is not the only binding for a system reset device, right? 
So those others reset devices will need 'priority' too. For a given 
property, there should only be one schema definition defining the type 
for the property. Otherwise, there might be conflicts. So you need a 
common schema doing that. And here you would just have 'priority: true' 
or possibly some binding specific constraints.

Rob