Re: [PATCH v6 3/6] dt/bindings: add bindings for optee

Jens Wiklander
2015-11-19T09:18:22Z

On Mon, Nov 16, 2015 at 11:01:10AM -0600, Rob Herring wrote:
> On Thu, Oct 29, 2015 at 09:21:25AM +0100, Jens Wiklander wrote:
> > Introduces optee prefix and adds bindings for ARM TrustZone based OP-TEE
> > implementation.
> >
> > Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
> > ---
> > .../bindings/arm/firmware/optee,optee-tz.txt | 29 ++++++++++++++++++++++
> > .../devicetree/bindings/vendor-prefixes.txt | 1 +
> > 2 files changed, 30 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/arm/firmware/optee,optee-tz.txt
> >
> > diff --git a/Documentation/devicetree/bindings/arm/firmware/optee,optee-tz.txt b/Documentation/devicetree/bindings/arm/firmware/optee,optee-tz.txt
> > new file mode 100644
> > index 0000000..0a8ed0d
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/arm/firmware/optee,optee-tz.txt
> > @@ -0,0 +1,29 @@
> > +OP-TEE Device Tree Bindings
> > +
> > +OP-TEE is a piece of software using hardware features to provide a Trusted
> > +Execution Environment. The security can be provided with ARM TrustZone, but
> > +also by virtualization or a separate chip. As there's no single OP-TEE
> > +vendor we're using "optee" as the first part of compatible property,
> > +indicating the OP-TEE protocol is used when communicating with the secure
> > +world.
> > +
> > +* OP-TEE based on ARM TrustZone required properties:
> > +
> > +- compatible : should contain "optee,optee-tz"
>
> I would leave off optee as a vendor. Different implementations by
> vendors should then add their vendor prefix as they all have the chance
> to screw-up something. I suppose we could do "linaro" as the reference
> implementation.

OK, I'll use "linaro" then.

>
> > +
> > +- method : The method of calling the OP-TEE Trusted OS. Permitted
> > + values are:
> > +
> > + "smc" : SMC #0, with the register assignments specified
> > + in drivers/tee/optee/optee_smc.h
> > +
> > + "hvc" : HVC #0, with the register assignments specified
> > + in drivers/tee/optee/optee_smc.h
>
> The use here would be a guest VM calling thru to hypervisor and then
> hypervisor calling optee?

Yes, the hypervisor needs to be involved (translating IPA to PA etc)
when invoking secure world.

>
> > +
> > +
> > +
> > +Example:
> > + optee {
>
> This should go under a /firmware node similar to
> Documentation/devicetree/bindings/arm/firmware/tlm,trusted-foundations.txt.

I tried that and discovered that a
compatible = "simple-bus";
is needed for the firmware node for optee to get probed. Is it OK to write
the example as:

firmware {
compatible = "simple-bus";

optee {
...

Thanks,
Jens