On Tue, Mar 13, 2018 at 11:36:25AM -0400, Stephen Douthit wrote:
> On 03/13/2018 10:40 AM, Stefan Berger wrote:
> > I think that should be a first test, maybe also for CRB.
> 
> I don't think we can make that the first test.  If we don't wait for
> tpmRegValidSts (qualified by some known zero bit), then we can't tell
> the difference between no-TPM, and reading before the device is ready.
> 
> Note 2 in section 6.6 of the TIS 1.3 spec:
> 
> 2. Within 30 milliseconds of the completion of TPM_Init:
>   a. All fields within the access register and all other registers MUST
>      return with the state of all their fields valid (i.e.
>      TPM_ACCESS_x.tpmRegValidSts is set to ‘1’).
>   b. The TPM MUST be ready to receive a command

I'm not sure of the specifics with the TPM.  But, as a general rule of
thumb, the SeaBIOS code can assume it's been over 30ms since power was
turned on to the machine.

-Kevin

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