Re: [PATCH v2 2/2] tpm_crb: Raise durations for Amazon NitroTPM

[Graf (AWS), Alexander]

On 16.10.26 18:27, Jonathan McDowell wrote:
> On Fri, Oct 16, 2026 at 04:37:33AM +0000, Surendran Kanagaraj wrote:
>> TPM commands need to complete within the command duration defined in
>> the TPM2 spec or keep answering TPM2_RC_RETRY for at most
>> TPM2_DURATION_LONG (2s).
>>
>> In rare scenarios NitroTPM can enter a mode where it either sends
>> TPM2_RC_RETRY for more than 2s or delays command completion. When
>> this happens during auth session start, the driver disables the chip
>> and every subsequent request fails:
>>
>>      tpm tpm0: in retry loop
>>      tpm tpm0: tpm2_load_context: failed with a TPM error 0x0922
>>
>> Add support for vendor duration overrides to the CRB driver, based on
>> the vendor ID read from the interface ID register. For NitroTPM, raise
>> TPM_SHORT, TPM_MEDIUM and TPM_LONG to 30s which covers the longest
>> unavailability time along with some headroom.
> Bumping all of these to 30s seems excessive. Is it really the case that
> all commands can potentially take this long? Is that because of
> non-TPM-related operations Nitro might be doing behind the scenes?


We won't reach the 30s, which is exactly why it's a safe default for the 
safety net that these timeouts are :).


Alex