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Date: Sun, 24 Mar 2024 04:14:36 +0200
Message-Id: <D01M8YKG5ZG0.287OTMCUU2KP5@kernel.org>
Subject: Re: [PATCH v4] Documentation: tpm_tis
From: "Jarkko Sakkinen" <jarkko@kernel.org>
To: "Jarkko Sakkinen" <jarkko@kernel.org>, "Daniel P. Smith"
 <dpsmith@apertussolutions.com>, <linux-integrity@vger.kernel.org>
Cc: "Jonathan Corbet" <corbet@lwn.net>, "Lino Sanfilippo"
 <l.sanfilippo@kunbus.com>, "Jason Gunthorpe" <jgg@ziepe.ca>, "Peter Huewe"
 <peterhuewe@gmx.de>, "James Bottomley"
 <James.Bottomley@HansenPartnership.com>, "Alexander Steffen"
 <Alexander.Steffen@infineon.com>, <keyrings@vger.kernel.org>,
 <linux-doc@vger.kernel.org>, <linux-kernel@vger.kernel.org>, "Randy Dunlap"
 <rdunlap@infradead.org>, "Richard Cochran" <richardcochran@gmail.com>,
 "open list:PTP HARDWARE CLOCK SUPPORT:Keyword:(?:b|_)ptp(?:b|_)"
 <netdev@vger.kernel.org>
References: <20240322123542.24158-1-jarkko@kernel.org>
 <5a494de5-b004-440c-bcdf-7bdfa3a8c508@apertussolutions.com>
 <D01CLI2TC5SZ.1A48PDHM5F3UA@kernel.org>
In-Reply-To: <D01CLI2TC5SZ.1A48PDHM5F3UA@kernel.org>

On Sat Mar 23, 2024 at 8:40 PM EET, Jarkko Sakkinen wrote:
> > Would it be worth clarifying here that one of those interfaces is=20
> > defined in the Mobile TPM specification, which also refers to its=20
> > interface as the CRB interface. In the past, this has caused great=20
> > confusion when working with individuals from the embedded community,=20
> > e.g., Arm. The Mobile TPM CRB interface, which can also be found being=
=20
> > used by some generations of AMD fTPM, is a doorbell style interface=20
> > using general-purpose memory. I would also point out that the Mobile TP=
M=20
> > CRB interface does not provide for the concept of localities.
>
> I don't necessarily disagree but it is out of scope for this. I'm not
> sure tho why "mobile" CRB would ever need that sort of separate
> dicussion.
>
> Some CRB implementations have localities some don't, and also fTPM
> implementations on x86 vary, no need to state that separately for
> mobile.

I.e. the variance exist but it is not "mobile" specific.

E.g. when I developed tpm_crb in 2014 at that time Intel PTT only
had a single locality (AFAIK later multiple localities were added
to support TXT).

In all cases this tpm_crb discussion is not really part of tpm_tis
discussion.

BR, Jarkko