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

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Message-ID: <20210223185610.7f495406@xps13>
Date:   Tue, 23 Feb 2021 18:56:10 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     richard@....at, vigneshr@...com, robh+dt@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-mtd@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        boris.brezillon@...labora.com
Subject: Re: [PATCH 2/3] dt-bindings: mtd: Add a property to declare secure
 regions in Qcom NANDc

Hi Manivannan,

Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org> wrote on Tue,
23 Feb 2021 23:15:46 +0530:

> Hi Miquel,
> 
> On Tue, Feb 23, 2021 at 05:49:22PM +0100, Miquel Raynal wrote:
> > Hi Manivannan,
> > 
> > Manivannan Sadhasivam <manivannan.sadhasivam@...aro.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@...aro.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.

Absolutely, I was just wondering why you mentioned it here. I don't
think it's useful, you can drop it.

> 
> > 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  


Thanks,
Miquèl