Re: [PATCH 1/1] tpm: disable hwrng for fTPM on some AMD designs

[Jarkko Sakkinen]

On Fri Jul 28, 2023 at 8:18 PM UTC, Daniil Stas wrote:
> On Fri, 28 Jul 2023 19:30:18 +0000
> "Jarkko Sakkinen" <jarkko@xxxxxxxxxx> wrote:
>
> > On Thu Jul 27, 2023 at 3:38 PM UTC, Daniil Stas wrote:
> > > Hi,
> > > I am still getting fTPM stutters with 6.4.3 kernel on Asus GA402RJ
> > > laptop.
> > > Compiling kernel without TPM support makes the stutters go away.
> > > The fTPM firmware version is 0x3005700020005 on my machine.  
> > 
> > This is needs a bit more elaboration in order to be comprehended.
> > 
> > Do you mean by "stutter" unexpected delays and when do they happen?
> > 
> > BR, Jarkko
>
> Yes, unexpected delays. They just happen randomly.
> You can google "AMD fTPM stuttering", there are a lot of examples.
> Here is one: https://www.youtube.com/watch?v=TYnRL-x6DVI

What if you make tpm_amd_is_rng_defective() to unconditonally return
true? Does this make the problem dissappear, or not?

BR, Jarkko