firmware/lib/tpm2_lite/tlcl.c
/**
 * The name of the function was kept to maintain the existing TPM API, but
 * TPM2.0 does not use the global lock to protect the FW rollback counter.
 * Instead it calls WriteLock for the FW NVRAM index to prevent future
 * writes to it.
 *
 * It first checks if the platform hierarchy is already disabled, and does
 * nothing, if so. Otherwise, WriteLock for the index obviously fails.
 */
The name of the function was kept to maintain the existing TPM API, but
TPM2.0 does not use the global lock to protect the FW rollback counter.
Instead it calls WriteLock for the FW NVRAM index to prevent future
writes to it.

It first checks if the platform hierarchy is already disabled, and does
nothing, if so. Otherwise, WriteLock for the index obviously fails.
The name of the function was kept to maintain the existing TPM API but TPM2 . 0 does not use the global lock to protect the FW rollback counter . Instead it calls WriteLock for the FW NVRAM index to prevent future writes to it . It first checks if the platform hierarchy is already disabled and does nothing if so . Otherwise WriteLock for the index obviously fails .
uint32_t TlclSetGlobalLock(void)
{
	if (tpm_is_ph_disabled())
		return TPM_SUCCESS;
	else
		return tlcl_lock_nv_write(FIRMWARE_NV_INDEX);
}
uint32_t TlclSetGlobalLock ( void ) { if ( tpm_is_ph_disabled ( ) ) return TPM_SUCCESS ; else return tlcl_lock_nv_write ( FIRMWARE_NV_INDEX ) ; }
The name of the function was kept to maintain the existing TPM API, but
 TPM2.0 does not use the global lock to protect the FW rollback counter.
The name of the function was kept to maintain the existing TPM API but TPM2 . 0 does not use the global lock to protect the FW rollback counter .