Re: [PATCH v2 1/6] dt-bindings: reserved-memory: Add Owl SoC serial number binding

[Cristian Ciocaltea <cristian.ciocaltea@gmail.com>]

On Thu, Apr 01, 2021 at 12:07:04PM -0500, Rob Herring wrote:
> On Tue, Mar 30, 2021 at 04:48:16PM +0300, Cristian Ciocaltea wrote:
> > Add devicetree binding for the Actions Semi Owl SoC serial number
> > reserved-memory range.
> > 
> > Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
> > ---
> >  .../actions,owl-soc-serial.yaml               | 53 +++++++++++++++++++
> >  1 file changed, 53 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/reserved-memory/actions,owl-soc-serial.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/reserved-memory/actions,owl-soc-serial.yaml b/Documentation/devicetree/bindings/reserved-memory/actions,owl-soc-serial.yaml
> > new file mode 100644
> > index 000000000000..41b71f47ee6c
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/reserved-memory/actions,owl-soc-serial.yaml
> > @@ -0,0 +1,53 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/reserved-memory/actions,owl-soc-serial.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Actions Semi Owl reserved-memory for SoC serial number
> > +
> > +maintainers:
> > +  - Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
> > +
> > +description: |
> > +  Provide access to the memory region where the two parts of the Actions
> > +  Semi Owl SoC serial number (low & high) can be read from. This information
> > +  is provided by the bootloader, hence expose it under /reserved-memory node.
> > +
> > +  Please refer to reserved-memory.txt in this directory for common binding
> > +  part and usage.
> > +
> > +  This is currently supported only on the S500 SoC variant.
> > +
> > +properties:
> > +  compatible:
> > +    oneOf:
> > +      - const: actions,owl-soc-serial
> > +      - items:
> > +          - enum:
> > +              - actions,s500-soc-serial
> > +          - const: actions,owl-soc-serial
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +
> > +additionalProperties: true
> > +
> > +examples:
> > +  - |
> > +    reserved-memory {
> > +        #address-cells = <1>;
> > +        #size-cells = <1>;
> > +        ranges;
> > +
> > +        soc_serial: soc-serial@800 {
> > +            compatible = "actions,s500-soc-serial", "actions,owl-soc-serial";
> > +            reg = <0x800 0x8>;
> 
> You end up wasting a whole page of memory for 8 bytes. It may be better 
> to copy this to a DT property ('serial-number' is already a defined root 
> property).

Actually there is more information provided by the vendor bootloader
in this memory page, so we might use it once we are able to decode it.
For the moment I could only identify the serial number.

Thanks,
Cristi

> Rob