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

[Stefan Berger <stefanb@linux.ibm.com>]

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