linux-kernel - Re: [PATCH v6 1/5] ARM: add basic support for Trusted Foundations

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Date:	Tue, 17 Sep 2013 12:28:53 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Alexandre Courbot <acourbot@...dia.com>,
	Russell King <linux@....linux.org.uk>,
	Tomasz Figa <t.figa@...sung.com>,
	Dave Martin <Dave.Martin@....com>,
	Olof Johansson <olof@...om.net>, Arnd Bergmann <arnd@...db.de>,
	Kevin Hilman <khilman@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6 1/5] ARM: add basic support for Trusted Foundations

On Tue, Sep 17, 2013 at 1:50 AM, Stephen Warren <swarren@...dotorg.org> wrote:
> On 09/15/2013 03:40 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).
>
>> diff --git a/arch/arm/firmware/trusted_foundations.c b/arch/arm/firmware/trusted_foundations.c
>
>> +#if IS_ENABLED(CONFIG_OF)
>> +void of_register_trusted_foundations(void)
>> +{
>> +     struct device_node *node;
>> +     struct trusted_foundations_platform_data pdata;
>> +     int err;
>> +
>> +     node = of_find_compatible_node(NULL, NULL, "tl,trusted-foundations");
>> +     if (!node)
>> +             return;
> ...
>
>> diff --git a/arch/arm/include/asm/trusted_foundations.h b/arch/arm/include/asm/trusted_foundations.h
>
>> +#if IS_ENABLED(CONFIG_TRUSTED_FOUNDATIONS)
>> +void register_trusted_foundations(struct trusted_foundations_platform_data *pd);
>> +#if IS_ENABLED(CONFIG_OF)
>> +void of_register_trusted_foundations(void);
>> +#endif
>
> I still don't think that's correct.
>
> If TF support is enabled, yet DT support is not enabled, then there is
> no prototype, implementation, or dummy implementation for
> of_register_trusted_foundations(). I think there should be a dummy
> implementation in this case, shouldn't there?
>
>> +
>> +#else /* CONFIG_TRUSTED_FOUNDATIONS */
>> +
>> +#include <linux/printk.h>
>> +#include <linux/of.h>
>> +#include <asm/bug.h>
>> +
>> +static inline void register_trusted_foundations(
>> +                                struct trusted_foundations_platform_data *pd)
>> +{
>> +     panic("No support for Trusted Foundations, stopping...\n");
>> +}
>> +
>> +#if IS_ENABLED(CONFIG_OF)
>> +static inline void of_register_trusted_foundations(void)
>> +{
>> +     /* If we find the target should enable TF but does not support it,
>> +      * fail as the system won't be able to do much anyway */
>> +     if (of_find_compatible_node(NULL, NULL, "tl,trusted-foundations"))
>> +             register_trusted_foundations(NULL);
>> +}
>> +#else
>> +static inline void of_register_trusted_foundations(void)
>> +{
>> +}
>> +#endif /* CONFIG_OF */
>
> That's more complex than it needs to be; there is a dummy
> of_find_compatible_node() in the !OF case, so you don't need to ifdef
> the implementation of of_register_trusted_foundations(); you just need
> the first implementation here.
>
>> +#endif /* CONFIG_TRUSTED_FOUNDATIONS */
>
> In summary, I think you need:
>
> If TF is enabled, always implement of_register_trusted_foundations() in
> the C file, and rely on of_find_compatible_node() to return NULL if
> !CONFIG_OF.
>
> If TF is not enabled, implement the inline version in the header file,
> and again rely on of_find_compatible_node() to return NULL if !CONFIG_OF.

Indeed, all your points are correct, and I've clearly been negligent
here. Sorry about that.

Will have to submit a v7, but hopefully we can get the acks that we
need (Russel?) on this version.

Alex.
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