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SubjectRe: [RFC PATCH 1/2] dt-bindings: arm: Add secure-clocks binding description
On Sat, 25 Apr 2020 at 00:06, Rob Herring <robh+dt@kernel.org> wrote:
>
> On Thu, Apr 23, 2020 at 1:49 AM Etienne Carriere
> <etienne.carriere@linaro.org> wrote:
> >
> > Describe how clocks property can leverage secure- property prefix
> > for clocks handled exclusively or shared by secure and non-secure
> > worlds.
> >
> > Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
> > ---
> > .../devicetree/bindings/arm/secure.txt | 19 +++++++++++++++++++
> > 1 file changed, 19 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/arm/secure.txt b/Documentation/devicetree/bindings/arm/secure.txt
> > index f27bbff2c780..9bc94921f2a6 100644
> > --- a/Documentation/devicetree/bindings/arm/secure.txt
> > +++ b/Documentation/devicetree/bindings/arm/secure.txt
> > @@ -53,6 +53,25 @@ Valid Secure world properties
> > status = "disabled"; /* disabled in both */
> > status = "disabled"; secure-status = "disabled"; /* disabled in both */
> >
> > +- secure-clocks : specifies the Phandle list secure world shall use
> > + for the related clocks whereas property "clocks" specifies the
> > + clock Phandle list non-secure shall use for the that clocks.
> > + This configuration can apply for example when a hardware clock is
> > + shared by the 2 worlds and the hardware implements a specific interface
> > + for each world, i.e.:
> > +
> > + clocks = <&clk DMA_NS>; /* NS relies on clock handle DMA_NS */
> > + secure-clocks = <&clk DMA_S>; /* S relies on clock handle DMA_S */
>
> The device has to know what it's clocks are for and should know if
> some clocks are secure only.
>
> > + Another example where use of "clocks" and "secure-clocks" can apply
> > + is when hardware implements a clock that secure and non-secure must
> > + share, as a shared GPIO bank clock, and secure world relies on clock
> > + device driver whereas non-secure world relies on a software service
> > + exposed by secure world as SCMI clock device. I.e.:
> > +
> > + clocks = <&scmi_clk 2>; /* NS relies on SCMI resources */
> > + secure-clocks= <&clk 5>; /* S accesses the SoC reset interfaces */
>
> If you have this case, I don't think this is the solution. I don't
> think it scales well and you probably need separate DTs. It's
> something to solve in the system DT project.

Acked,

Thanks,
Etienne

>
> Rob

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