linux-kernel - Re: [PATCH] tpm: tis: Increase the default for timeouts B and C

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Message-ID: <Z-5qVBjeRfEdRAP5@earth.li>
Date: Thu, 3 Apr 2025 12:00:36 +0100
From: Jonathan McDowell <noodles@...th.li>
To: Michal Suchánek <msuchanek@...e.de>
Cc: Peter Huewe <peterhuewe@....de>, Jarkko Sakkinen <jarkko@...nel.org>,
	Jason Gunthorpe <jgg@...pe.ca>, linux-integrity@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tpm: tis: Increase the default for timeouts B and C

On Wed, Apr 02, 2025 at 10:07:39PM +0200, Michal Suchánek wrote:
>On Wed, Apr 02, 2025 at 06:45:40PM +0100, Jonathan McDowell wrote:
>> On Wed, Apr 02, 2025 at 07:21:30PM +0200, Michal Suchanek wrote:
>> > With some Infineon chips the timeouts in tpm_tis_send_data (both B and
>> > C) can reach up to about 2250 ms.
>> >
>> > Extend the timeout duration to accommodate this.
>>
>> The problem here is the bump of timeout_c is going to interact poorly with
>> the Infineon errata workaround, as now we'll wait 4s instead of 200ms to
>> detect the stuck status change.
>
>Yes, that's problematic. Is it possible to detect the errata by anything
>other than waiting for the timeout to expire?

Not that I'm aware of, nor have seen in my experimentation. It's a 
"stuck" status, so the timeout is how it's detected.

OOI, have you tried back porting the fixes that are in mainline for 6.15 
to your frankenkernel? I _think_ the errata fix might end up resolving 
at least the timeout for valid for you, as a side effect? We're 
currently rolling them out across our fleet, but I don't have enough 
runtime yet to be sure they've sorted all the timeout instances we see.

J.

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