[coreboot] SeaBIOS TPM support on Chromebook Acer C720

[Stefan Berger]

Hello!

I added support from the TPM to SeaBIOS and have parts of the BIOS 
functionality successfully running on a Chromebook Acer C720 (as example 
hardware). Here are some findings on the Acer:

The TPM is successfully detected but sending TPM_Startup(ST_Clear) to 
the TPM fails since either coreboot or some other firmware seems to 
already have initialized the TPM, which is fine, and also extended PCR 0 
with at least one hash. Ideally there would be a TCPA ACPI table 
containing information about what was logged, since otherwise the state 
of the PCR seems not that useful. SeaBIOS's TPM extensions could then 
also use this TCPA table and add its own logs into it along with 
extending PCRs in the TPM. So, in this case the TPM SeaBIOS extensions 
don't log anything and adding additional ACPI tables to the existing 
coreboot tables seems 'impractical'. I was wondering if coreboot could 
add such a table if a TPM was found to be present?

The latest set of TPM patches can be found here:

http://www.seabios.org/pipermail/seabios/2014-July/008178.html

Regards,
     Stefan