Stefan Berger of IBM submitted a 6-part patch to the SeaBIOS project, updating it’s TPM support, his patch comment follows:

This series of patches extends the TPM2 code to extend the BIOS related PCRs 0-7 in all available banks. This prevents that these PCRs remain untouched and filled with bogus values by applications. For example, the SHA1 hash is extended into the SHA256 bank. The value that is extended into this bank is essentially a SHA1 with zero bytes used for filling it to the size of a sha256 hash. This is done for all PCR banks of the TPM2 where these PCRs are available. In v2 of this series I also extended the log functions for logging the additional hashes. So there are more patches now.

For more information, see the full patch sent to the SeaBIOS list:
https://www.coreboot.org/mailman/listinfo/seabios