Re: [PATCH v7 0/3] Add support for TPM devices over I2C bus

[Stefan Berger]

On 3/27/23 04:04, Joel Stanley wrote:
> On Mon, 27 Mar 2023 at 03:52, Ninad Palsule <ninad@linux.vnet.ibm.com> wrote:
> > Hi Joel,
> >
> > On 3/26/23 8:05 PM, Joel Stanley wrote:
> > > Hi Ninad,
> > >
> > > On Sun, 26 Mar 2023 at 22:44, Ninad Palsule <ninad@linux.ibm.com> wrote:
> > > > Hello,
> > > >
> > > > I have incorporated review comments from Stefan. Please review.
> > > >
> > > > This drop adds support for the TPM devices attached to the I2C bus. It
> > > > only supports the TPM2 protocol. You need to run it with the external
> > > > TPM emulator like swtpm. I have tested it with swtpm.
> > > Nice work. I tested these stop cedric's aspeed-8.0 qemu tree, using
> > > the rainier machine and the openbmc dev-6.1 kernel.
> > >
> > > We get this message when booting from a kernel:
> > >
> > > [    0.582699] tpm_tis_i2c 12-002e: 2.0 TPM (device-id 0x1, rev-id 1)
> > > [    0.586361] tpm tpm0: A TPM error (256) occurred attempting the self test
> > > [    0.586623] tpm tpm0: starting up the TPM manually
> > >
> > > Do we understand why the error appears?
> >
> >
> > Yes, As per kernel code this is an expected error for some emulators.
> >
> > On swtpm emulator, It returns TPM2_RC_INITIALIZE if emulator is not
> > initialized. I searched it in swtpm and it indicated that selftest
> > requested before it is initialized. I meant to ask Stefan but busy with
> > the review comments.
>
> The swtpm man page mentions some flags we can set. Perhaps they would help?
>
>         --flags [not-need-init]
> [,startup-clear|startup-state|startup-deactivated|startup-none]

With firmware initializing the TPM 2 neither of these options is necessary.
If firmware doesn't initialize the TPM 2 then Linux will show that error 
message and initialize it.



   Stefan