linux-kernel - MSI B350M MORTAR: tpm tpm0: AMD fTPM version 0x3005700000004 causes system stutter; hwrng disabled

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Date:   Sun, 25 Jun 2023 10:20:22 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Mario Limonciello <mario.limonciello@....com>,
        "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-integrity@...r.kernel.org,
        Jarkko Sakkinen <jarkko@...nel.org>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Jason Gunthorpe <jgg@...pe.ca>, Peter Huewe <peterhuewe@....de>
Subject: MSI B350M MORTAR: tpm tpm0: AMD fTPM version 0x3005700000004 causes
 system stutter; hwrng disabled

Dear Mario, dear Jason, dear Linux folks,

Thank you for your great work on the Linux kernel.

On an MSI MS-7A37/B350M MORTAR (MS-7A37) even updating to their latest 
system firmware 1.O7 released on their Web site on May, 23rd 2023 [1].

> Beschreibung:
> -  AGESA ComboAm4v2PI 1.2.0.A. update.
> -  TPM Out of Bounds Access security patch.

But Linux 6.4.-rc7 still disables the hwrng from AMD fTPM.

     Jun 24 21:32:09.978772 tokeiihto kernel: DMI: Micro-Star 
International Co., Ltd. MS-7A37/B350M MORTAR (MS-7A37), BIOS 1.O7 05/09/2023
     […]
     Jun 24 21:32:10.259986 tokeiihto kernel:  tpm tpm0: AMD fTPM 
version 0x3005700000004 causes system stutter; hwrng disabled

Unfortunately, the warning does not say, what firmware version is 
needed, and what the user can do about it.

The comment in the code, added in v6.3-rc2 with commit f1324bbc4011 
(tpm: disable hwrng for fTPM on some AMD designs) [2], says:

     /*
      * Some AMD fTPM versions may cause stutter
      * https://www.amd.com/en/support/kb/faq/pa-410
      *
      * Fixes are available in two series of fTPM firmware:
      * 6.x.y.z series: 6.0.18.6 +
      * 3.x.y.z series: 3.57.y.5 +
      */

Mapping 0x3005700000004 from the Linux warning to the comment, I assume 
the board’s firmware is 3.57.0.4?

What AGESA ComboAm4v2PI would MSI need to ship, so the issue is fixed? 
The previous system firmware version shipped 3.4e.0.4? (Is it decimal or 
hexadecimal?)

     [  282.864564] tpm tpm0: AMD fTPM version 0x3004e00000004 causes 
system stutter; hwrng disabled

Kind regards,

Paul

[1]: https://de.msi.com/Motherboard/B350M-MORTAR/support#bios
[2]: 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f1324bbc4011ed8aef3f4552210fc429bcd616da