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

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Date:   Wed, 10 Mar 2021 09:15:14 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Miquèl Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh R <vigneshr@...com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        MTD Maling List <linux-mtd@...ts.infradead.org>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Boris Brezillon <boris.brezillon@...labora.com>
Subject: Re: [PATCH 2/3] dt-bindings: mtd: Add a property to declare secure
 regions in Qcom NANDc

On Tue, Mar 09, 2021 at 07:32:28PM -0700, Rob Herring wrote:
> On Sun, Mar 7, 2021 at 10:31 PM Manivannan Sadhasivam
> <manivannan.sadhasivam@...aro.org> wrote:
> >
> > On Fri, Mar 05, 2021 at 05:36:57PM -0600, Rob Herring wrote:
> > > On Mon, Feb 22, 2021 at 05:32:58PM +0530, Manivannan Sadhasivam wrote:
> > > > 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
> > >
> > > Don't you need 64-bit regions potentially? Though 4GB should be enough
> > > for anyone.
> > >
> >
> > Yes, given the size of current NAND based systems around, I thought 32 bit is
> > enough.
> 
> Huh!? I was joking. 4GB is small nowadays. Make this 64-bit.
> 

Well I was speaking in the context of Qcom chipsets making use of NAND. Mostly
the Qcom modem chipsets have <4GB of memory. But since this property is now not
specific to Qcom, I agree with you and will make it 64 bit.

Thanks,
Mani

> Rob