Hi Ilias, On Mon, 5 Oct 2026 at 10:48, Ilias Apalodimas <[email protected]> wrote: > Do you have a real world use case where an OS wants a TPM with zero > preboot measurements?
Yes. On some of our i.MX8 based devices Linux uses the TPM for disk encryption and for device certificates. Platform integrity is established by other means, so nothing is sealed against PCRs and there are no preboot measurements. Disabling the TPM in the DT is therefore not an option for us, as Linux needs it. What I am really after is that Linux finds the TPM in the same state on all our products, whichever SoC they use and whether or not they use measurements, as it does on UEFI platforms where the firmware always starts the TPM. Today that depends on the boot path in U-Boot: EFI or MEASURED_BOOT start it, a plain booti/bootm does not, and Linux then logs "A TPM error (256) occurred attempting the self test" and starts it itself. How U-Boot does that, in probe or from an event, is less important to me. I am happy to implement whichever you prefer for v2. Regards, Michael
