Re: [PATCH v9 1/5] ARM: add basic support for Trusted Foundations

[Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>]

On Mon, Oct 28, 2013 at 11:31:36PM +0000, Tomasz Figa wrote:
> On Monday 28 of October 2013 14:56:49 Olof Johansson wrote:
> > On Mon, Oct 28, 2013 at 05:57:04AM -0500, Kumar Gala wrote:
> > > On Oct 28, 2013, at 5:28 AM, Alexandre Courbot wrote:
> > > > Trusted Foundations is a TrustZone-based secure monitor for ARM that
> > > > can be invoked using the same SMC-based API on all supported
> > > > platforms. This patch adds initial basic support for Trusted
> > > > Foundations using the ARM firmware API. Current features are limited
> > > > to the ability to boot secondary processors.
> > > > 
> > > > Note: The API followed by Trusted Foundations does *not* follow the
> > > > SMC
> > > > calling conventions. It has nothing to do with PSCI neither and is
> > > > only
> > > > relevant to devices that use Trusted Foundations (like most
> > > > Tegra-based
> > > > retail devices).
> > > > 
> > > > Signed-off-by: Alexandre Courbot <acourbot-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> > > > Reviewed-by: Tomasz Figa <t.figa-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
> > > > Reviewed-by: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> > > > ---
> > > > .../arm/firmware/tl,trusted-foundations.txt        | 20 ++++++
> > > > .../devicetree/bindings/vendor-prefixes.txt        |  1 +
> > > > arch/arm/Kconfig                                   |  2 +
> > > > arch/arm/Makefile                                  |  1 +
> > > > arch/arm/firmware/Kconfig                          | 28 ++++++++
> > > > arch/arm/firmware/Makefile                         |  1 +
> > > > arch/arm/firmware/trusted_foundations.c            | 79
> > > > ++++++++++++++++++++++ arch/arm/include/asm/trusted_foundations.h  
> > > >       | 67 ++++++++++++++++++ 8 files changed, 199 insertions(+)
> > > > create mode 100644
> > > > Documentation/devicetree/bindings/arm/firmware/tl,trusted-foundatio
> > > > ns.txt create mode 100644 arch/arm/firmware/Kconfig
> > > > create mode 100644 arch/arm/firmware/Makefile
> > > > create mode 100644 arch/arm/firmware/trusted_foundations.c
> > > > create mode 100644 arch/arm/include/asm/trusted_foundations.h
> > > > 
> > > > diff --git
> > > > a/Documentation/devicetree/bindings/arm/firmware/tl,trusted-foundat
> > > > ions.txt
> > > > b/Documentation/devicetree/bindings/arm/firmware/tl,trusted-foundat
> > > > ions.txt new file mode 100644
> > > > index 0000000..2ec75c9
> > > > --- /dev/null
> > > > +++
> > > > b/Documentation/devicetree/bindings/arm/firmware/tl,trusted-foundat
> > > > ions.txt @@ -0,0 +1,20 @@
> > > > +Trusted Foundations
> > > > +-------------------
> > > > +
> > > > +Boards that use the Trusted Foundations secure monitor can signal
> > > > its
> > > > +presence by declaring a node compatible with
> > > > "tl,trusted-foundations"
> > > > +under the /firmware/ node
> > > > +
> > > > +Required properties:
> > > > +- compatible : "tl,trusted-foundations"
> > > > +- version-major : major version number of Trusted Foundations
> > > > firmware
> > > > +- version-minor: minor version number of Trusted Foundations
> > > > firmware
> > > 
> > > vendor prefix version.
> > 
> > Are you saying he should use tl,version-major tl,version-minor? For
> > bindings that are already vendor-specific we haven't (on ARM) asked for
> > vendor prefix on properties. It doesn't mean that we should keep going
> > down that route though, so I'm just asking for clarification for my own
> > edification. :)
> 
> This is a good question. We should decide what the right thing (TM) is and 
> write it down. I, on the contrary, was convinced that it's the way Kumar 
> says.

The impression I got was that properties should be prefixed when they're
extremely vendor-specific and could clash with a more generic property. I'm not
sure that firmware will ever have a generic binding given the variation even in
the set of implemented functionality.

I would imagine that there are many ways different firmwares might be
versioned, and I can't see version-major or version-minor clashing with a
generic property we might add later. However prefixing would not be harmful, so
I'm not opposed to it if others want that.

Another option would be to support a fallback compatible list (e.g.
"tl,trusted-foundations-${MAJOR}-${MINOR}", "tl,trusted-foundations"), and get
versioning information from there. Given that could be painful to handle I
don't want to force it if not required.

Thanks,
Mark.