Re: [PATCH 2/3] dt-bindings: mtd: Add a property to declare secure regions in Qcom NANDc

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

Hi Miquel,

On Tue, Feb 23, 2021 at 05:49:22PM +0100, Miquel Raynal wrote:
> Hi Manivannan,
> 
> Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> wrote on Mon,
> 22 Feb 2021 17:32:58 +0530:
> 
> > On a typical end product, a vendor may choose to secure some regions in
> > the NAND memory which are supposed to stay intact between FW upgrades.
> > The access to those regions will be blocked by a secure element like
> > Trustzone. So the normal world software like Linux kernel should not
> > touch these regions (including reading).
> > 
> > So let's add a property for declaring such secure regions so that the
> > driver can skip touching them.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> > ---
> >  Documentation/devicetree/bindings/mtd/qcom,nandc.yaml | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/mtd/qcom,nandc.yaml b/Documentation/devicetree/bindings/mtd/qcom,nandc.yaml
> > index 84ad7ff30121..7500e20da9c1 100644
> > --- a/Documentation/devicetree/bindings/mtd/qcom,nandc.yaml
> > +++ b/Documentation/devicetree/bindings/mtd/qcom,nandc.yaml
> > @@ -48,6 +48,13 @@ patternProperties:
> >          enum:
> >            - 512
> >  
> > +      qcom,secure-regions:
> > +        $ref: /schemas/types.yaml#/definitions/uint32-array
> > +        description:
> > +          Regions in the NAND memory which are protected using a secure element
> > +          like Trustzone. This property contains the start address and size of
> > +          the secure regions present (optional).
> 
> What does this "(optional)" means? If you mean the property is optional
> then it should be described accordingly in the yaml file, or am I
> missing something?
> 

IIUC, if a property is not listed under "required" section then it is
optional. But I've added the quote here to just make it explicit.

> I wonder if it wouldn't be better to make this a NAND chip node
> property. I don't think a qcom prefix is needed as potentially many
> other SoCs might have the same "feature".
> 
> I'm fine adding support for it in the qcom driver only though.
> 

Hmm, sounds good to me.

Thanks,
Mani

> > +
> >  allOf:
> >    - $ref: "nand-controller.yaml#"
> >  
> 
> Thanks,
> Miquèl