Re: [PATCH v5 1/5] ARM: add basic Trusted Foundations support

[Stephen Warren <swarren@wwwdotorg.org>]

On 09/09/2013 12:38 AM, Alexandre Courbot wrote:
> On Sat, Sep 7, 2013 at 4:29 AM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>> On 09/04/2013 09:27 PM, Alexandre Courbot wrote:
>>> Trusted Foundations is a TrustZone-based secure monitor for ARM that
>>> can be invoked  using a consistent 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.

>>> diff --git a/arch/arm/include/asm/trusted_foundations.h b/arch/arm/include/asm/trusted_foundations.h
>>
>> Do we need to add the following here:
>>
>> #if !IS_ENABLED(CONFIG_OF)
>> static inline void register_trusted_foundations(...) {}
>> #endif

Uggh. I meant to write **of_**register_trusted_foundations() there.

>> So that there is a dummy no-op function for the non-DT-support case? I
>> guess Tegra always has CONFIG_OF enabled so that call from
>> mach-tegra/common.c in patch 2 will never be an issue, but perhaps it
>> might if anyone else uses this?
> 
> My expectation is that register_trusted_foundations() is called by the
> platform code once it has established (through whatever mean it likes)
> that Trusted Foundations is required. For platforms supporting DT,
> of_register_trusted_foundations() takes care of that. Platforms that
> don't support DT need another way to decide whether they *need* TF or
> not. Once a platform decided that it needs TF, its absence is not an
> option, and therefore I'd think that register_trusted_foundations()
> should hard-fail if support is not compiled in. Or maybe I missed your
> point?

So yes, you missed my point, but it was my fault:-)

Most of_* can be called irrespective of CONFIG_OF, and since
of_register_trusted_foundations() is meant to handle internally the "do
I need to do anything" case, I think it makes sense to be allowed to
call it unconditionally without determining anything about either
CONFIG_OF or TF DT node presence?