linux-kernel - Re: tpm_tis TPM2.0 not detected on cold boot

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Message-Id: <3d57a904-81fc-f898-c9e0-1931da4aed3a@linux.ibm.com>
Date:   Mon, 31 Dec 2018 13:10:20 -0500
From:   Ken Goldman <kgold@...ux.ibm.com>
To:     Michael Niewöhner <linux@...ewoehner.de>,
        linux-integrity@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: tpm_tis TPM2.0 not detected on cold boot

On 12/30/2018 8:22 AM, Michael Niewöhner wrote:
>> difference is that on a cold boot, the TPM takes longer to initialize.
> Well, as I said. Waiting for 10, 20 or even 60 seconds in the boot manager does
> not solve the problem. So the problem is NOT that the TPM takes longer to
> initialize. Even adding a delay of 20 seconds before TPM init does not solve
> that while that should be more than enough time.
> 

This may be TPM hardware dependent.  As I understand it ...

A TPM is permitted to run it's self tests in the background after an
Init (cold boot) , but it's not required to do so.

A TPM that does not - that waits until one of the self test commands is 
issued - will appear to take longer to initialize.

In fact, it's not taking longer.  It's just waiting for some software
to issue a self test command, and will wait forever.