linux-kernel - Re: [RFC PATCH 3/4] dt-bindings: reserved-memory: add linaro,restricted-heap

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Message-ID: <CAHUa44Fd-Eo5-CUfxDgCFpRVbJP0gzA7LX_-5=cBfBd8NxhpDw@mail.gmail.com>
Date: Fri, 30 Aug 2024 10:42:32 +0200
From: Jens Wiklander <jens.wiklander@...aro.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	linaro-mm-sig@...ts.linaro.org, op-tee@...ts.trustedfirmware.org, 
	linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, 
	Olivier Masse <olivier.masse@....com>, Thierry Reding <thierry.reding@...il.com>, 
	Yong Wu <yong.wu@...iatek.com>, Sumit Semwal <sumit.semwal@...aro.org>, 
	Benjamin Gaignard <benjamin.gaignard@...labora.com>, Brian Starkey <Brian.Starkey@....com>, 
	John Stultz <jstultz@...gle.com>, "T . J . Mercier" <tjmercier@...gle.com>, 
	Christian König <christian.koenig@....com>, 
	Sumit Garg <sumit.garg@...aro.org>, Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Subject: Re: [RFC PATCH 3/4] dt-bindings: reserved-memory: add linaro,restricted-heap

On Fri, Aug 30, 2024 at 10:20 AM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On Fri, Aug 30, 2024 at 09:03:50AM +0200, Jens Wiklander wrote:
> > From: Olivier Masse <olivier.masse@....com>
> >
> > DMABUF reserved memory definition for OP-TEE secure data path feature.
> >
> > Signed-off-by: Olivier Masse <olivier.masse@....com>
> > Signed-off-by: Jens Wiklander <jens.wiklander@...aro.org>
> > ---
> >  .../linaro,restricted-heap.yaml               | 56 +++++++++++++++++++
> >  1 file changed, 56 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/reserved-memory/linaro,restricted-heap.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/reserved-memory/linaro,restricted-heap.yaml b/Documentation/devicetree/bindings/reserved-memory/linaro,restricted-heap.yaml
> > new file mode 100644
> > index 000000000000..0ab87cf02775
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/reserved-memory/linaro,restricted-heap.yaml
> > @@ -0,0 +1,56 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/reserved-memory/linaro,restricted-heap.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Linaro Secure DMABUF Heap
> > +
> > +maintainers:
> > +  - Olivier Masse <olivier.masse@....com>
> > +
> > +description:
> > +  Linaro OP-TEE firmware needs a reserved memory for the
> > +  Secure Data Path feature (aka SDP).
> > +  The purpose is to provide a restricted memory heap which allow
> > +  the normal world OS (REE) to allocate/free restricted buffers.
> > +  The TEE is reponsible for protecting the SDP memory buffers.
> > +  TEE Trusted Application can access restricted memory references
> > +  provided as parameters (DMABUF file descriptor).
>
> And what is the difference from regular reserved memory? Why it cannot
> be used?

Good question. I need a compatible = "linaro,restricted-heap" to find
it, but it appears that's permitted with regular reserved memory.
Let's drop this patch. Thanks for pointing me in the right direction.

>
> > +
> > +allOf:
> > +  - $ref: "reserved-memory.yaml"
>
> It does not look like you tested the bindings, at least after quick
> look. Please run  (see
> Documentation/devicetree/bindings/writing-schema.rst for instructions).
> Maybe you need to update your dtschema and yamllint.

You're right, sorry.

>
> > +
> > +properties:
> > +  compatible:
> > +    const: linaro,restricted-heap
> > +
> > +  reg:
> > +    description:
> > +      Region of memory reserved for OP-TEE SDP feature
> > +
> > +  no-map:
> > +    $ref: /schemas/types.yaml#/definitions/flag
> > +    description:
> > +      Avoid creating a virtual mapping of the region as part of the OS'
> > +      standard mapping of system memory.
> > +
> > +unevaluatedProperties: false
>
> This goes after "required:" block.

OK

>
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - no-map
> > +
> > +examples:
> > +  - |
> > +  reserved-memory {
> > +    #address-cells = <2>;
> > +    #size-cells = <2>;
> > +
> > +    sdp@...00000 {
> > +      compatible = "linaro,restricted-heap";
> > +      no-map;
> > +      reg = <0 0x3E800000 0 0x00400000>;
>
> lowercase hex
>

OK


Thanks,
Jens

> Best regards,
> Krzysztof
>