Re: [GIT PULL 1/7] soc/tegra: Changes for v5.20-rc1

From: Jon Hunter <jonathanh@nvidia.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Thierry Reding <thierry.reding@gmail.com>,
	arm-soc <arm@kernel.org>, SoC Team <soc@kernel.org>,
	"open list:TEGRA ARCHITECTURE SUPPORT"
	<linux-tegra@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-edac@vger.kernel.org, Borislav Petkov <bp@alien8.de>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Tony Luck <tony.luck@intel.com>,
	James Morse <james.morse@arm.com>,
	Robert Richter <rric@kernel.org>
Subject: Re: [GIT PULL 1/7] soc/tegra: Changes for v5.20-rc1
Date: Thu, 14 Jul 2022 07:49:41 +0100	[thread overview]
Message-ID: <da970752-0d99-9c81-07d8-2eeb783093d3@nvidia.com> (raw)
In-Reply-To: <CAK8P3a1sDbtEUaT7Z5k_SfUcA7OBUxkny7kmKOMFaE96qaGeXg@mail.gmail.com>

On 13/07/2022 13:36, Arnd Bergmann wrote:
> On Wed, Jul 13, 2022 at 2:19 PM Jon Hunter <jonathanh@nvidia.com> wrote:
>> On 13/07/2022 13:14, Arnd Bergmann wrote:
>>>>> For the other patches, I found two more problems:
>>>>>
>>>>>> Bitan Biswas (1):
>>>>>>         soc/tegra: fuse: Expose Tegra production status
>>>>>
>>>>> Please don't just add random attributes in the soc device infrastructure.
>>>>> This one has a completely generic name but a SoC specific
>>>>> meaning, and it lacks a description in Documentation/ABI.
>>>>> Not sure what the right ABI is here, but this is something that needs
>>>>> to be discussed more broadly when you send a new version.
>>>>
>>>> I wasn't aware that the SoC device infrastructure was restricted to only
>>>> standardized attributes. Looks like there are a few other outliers that
>>>> add custom attributes: UX500, ARM Integrator and RealView, and OMAP2.
>>>>
>>>> Do we have some other place where this kind of thing can be exposed? Or
>>>> do we just need to come up with some better way of namespacing these?
>>>> Perhaps it would also be sufficient if all of these were better
>>>> documented so that people know what to look for on their platform of
>>>> interest.
>>>
>>> It's not a 100% strict rule, I've just tried to limit it as much as possible,
>>> and sometimes missed drivers doing it anyway. My main goal here is
>>> to make things consistent between SoC families, so if one piece of
>>> information is provided by a number of them, I'd rather have a standard
>>> attribute, or a common way of encoding this in the existing attributes
>>> than to have too many custom attributes with similar names.
>>
>>
>> Makes sense. Any recommendations for this specific attribute? I could
>> imagine other vendors may have engineering devices and production
>> versions. This is slightly different from the silicon version.
> 
> Not sure, I haven't seen this one referenced elsewhere so far.
> 
> What is the actual information this encodes in your case? Is this fused
> down in a way that production devices lose access to certain features
> that could be security critical but are useful for development?

Yes I believe it is precisely that. Exact details I am not clear on, but 
I see a lot of references to this throughout our userspace and testing 
code.

Jon

-- 
nvpublic

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel