linux-kernel - Re: [PATCH 1/4] dt-bindings: syscon: Add syscon endian properties support

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Message-ID: <20200313122634.lfdharbhxvnoew6r@ubsrv2.baikal.int>
Date:   Fri, 13 Mar 2020 15:26:34 +0300
From:   Sergey Semin <Sergey.Semin@...kalelectronics.ru>
To:     Rob Herring <robh@...nel.org>
CC:     Lee Jones <lee.jones@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Paul Burton <paulburton@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] dt-bindings: syscon: Add syscon endian properties
 support

On Thu, Mar 12, 2020 at 04:11:02PM -0500, Rob Herring wrote:
> On Fri, Mar 06, 2020 at 04:03:38PM +0300, Sergey.Semin@...kalelectronics.ru wrote:
> > From: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> > 
> > In accordance with the syscon-driver (drivers/mfd/syscon.c) the syscon
> > dts-nodes may accept endian properties of the boolean type: little-endian,
> > big-endian, native-endian. Lets make sure that syscon bindings json-schema
> > also supports them.
> > 
> > Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> > Signed-off-by: Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>
> > Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
> > Cc: Paul Burton <paulburton@...nel.org>
> > Cc: Ralf Baechle <ralf@...ux-mips.org>
> > ---
> >  Documentation/devicetree/bindings/mfd/syscon.yaml | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/mfd/syscon.yaml b/Documentation/devicetree/bindings/mfd/syscon.yaml
> > index 39375e4313d2..9ee404991533 100644
> > --- a/Documentation/devicetree/bindings/mfd/syscon.yaml
> > +++ b/Documentation/devicetree/bindings/mfd/syscon.yaml
> > @@ -61,6 +61,11 @@ properties:
> >      description:
> >        Reference to a phandle of a hardware spinlock provider node.
> >  
> > +patternProperties:
> > +  "^(big|little|native)-endian$":
> > +    $ref: /schemas/types.yaml#/definitions/flag
> > +    description: Bytes order of the system controller memory space.
> 
> Common properties should have a type definition in a common schema. For 
> this one, I'd like it in the core schema in dtschema. 

So what do you suggest then? Will you move this file to the dt-scheme/schemas
in your repo? What shall I do with this patch, just drop? Or would you like me
to fork your dt-schema repo, add dt-schemas/schemas/mfd/syscon.yaml file similar
to this one with "*-endian" property supported, then pull-request or
send a patch with the alteration back to your repo?

> 
> I'd expect for any specific 'syscon', either none or only a subset of 
> these are valid, so I don't think this should be added here.

AFAIU mfd/syscon.yaml describes a generic syscon compatible with generic
driver drivers/mfd/syscon.c, which may have any of these properties
declared in its dt-node. We can't predict which one because, well, it's
generic. At the same time, yes, only a subset of these properties can be
supported by a specific system controller, which one can be determined
by the controller specific dt schema. So if we left the property here in
the generic syscon.yaml, then the controller dt-schema would have had a
pattern like:

>
> allOf:
>   - $ref: ../../mfd/syscon.yaml#
>
> properties:
>   little-endian: true
>
> additionalProperties: false
>

as I did for soc/baikal-t1/be,bt1-l2-ctl.yaml. See the patch: "dt-bindings:
Add Baikal-T1 L2-cache Control Block dts bindings file" in the corresponding
patchset in your email Inbox.

Regards,
-Sergey

> 
> Rob