Date:	Tue, 29 Oct 2013 03:12:05 -0500
From:	Kumar Gala <galak@...eaurora.org>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Tomasz Figa <tomasz.figa@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Olof Johansson <olof@...om.net>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Kevin Hilman <khilman@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Pawel Moll <Pawel.Moll@....com>, Arnd Bergmann <arnd@...db.de>,
	Stephen Warren <swarren@...dotorg.org>,
	Tomasz Figa <t.figa@...sung.com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Alexandre Courbot <acourbot@...dia.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Dave P Martin <Dave.Martin@....com>
Subject: Re: [PATCH v9 1/5] ARM: add basic support for Trusted Foundations


On Oct 28, 2013, at 7:25 PM, Mark Rutland wrote:

> 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@...dia.com>
>>>>> Reviewed-by: Tomasz Figa <t.figa@...sung.com>
>>>>> Reviewed-by: Stephen Warren <swarren@...dia.com>
>>>>> ---
>>>>> .../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.

I'm of the opinion that making all vendor specific properties vendor prefixed is the easiest rule of thumb and leaves no gray area to have to argue about.

- k

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

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