linux-kernel - Re: [PATCH v4 2/3] dt-bindings: mtd: Add a property to declare secure regions in NAND chips

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Message-ID: <20210308101059.08658fbe@collabora.com>
Date:   Mon, 8 Mar 2021 10:10:59 +0100
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     miquel.raynal@...tlin.com, richard@....at, robh+dt@...nel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Daniele.Palmas@...it.com, bjorn.andersson@...aro.org
Subject: Re: [PATCH v4 2/3] dt-bindings: mtd: Add a property to declare
 secure regions in NAND chips

On Mon,  8 Mar 2021 11:14:46 +0530
Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org> 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
> drivers can skip touching them.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>  Documentation/devicetree/bindings/mtd/nand-controller.yaml | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mtd/nand-controller.yaml b/Documentation/devicetree/bindings/mtd/nand-controller.yaml
> index d0e422f4b3e0..15a674bedca3 100644
> --- a/Documentation/devicetree/bindings/mtd/nand-controller.yaml
> +++ b/Documentation/devicetree/bindings/mtd/nand-controller.yaml
> @@ -143,6 +143,13 @@ patternProperties:
>            Ready/Busy pins. Active state refers to the NAND ready state and
>            should be set to GPIOD_ACTIVE_HIGH unless the signal is inverted.
>  
> +      secure-regions:
> +        $ref: /schemas/types.yaml#/definitions/uint32-matrix
> +        description:
> +          Regions in the NAND chip which are protected using a secure element
> +          like Trustzone. This property contains the start address and size of
> +          the secure regions present.
> +

Since you declare this as a generic property, I think it'd be simpler
to do the check at the core level.

>      required:
>        - reg
>