On Wed, Jun 18, 2025 at 11:23:00AM +0100, Yeoreum Yun wrote:

To ensure the TPM device operating over the FF-A protocol with
the CRB interface is probed before IMA initialization,
the following conditions must be met:

   1. The corresponding ffa_device must be registered,
      which is done via ffa_init().

   2. The tpm_crb_driver must successfully probe this device via
      tpm_crb_ffa_init().

   3. The tpm_crb driver using CRB over FF-A can then
      be probed successfully. (See crb_acpi_add() and
      tpm_crb_ffa_init() for reference.)

Unfortunately, ffa_init(), tpm_crb_ffa_init(), and crb_acpi_driver_init() are
all registered with device_initcall, which means crb_acpi_driver_init() may
be invoked before ffa_init() and tpm_crb_ffa_init() are completed.

I get the ffa_init() part i.e, moving it earlier. However for
tpm_crb_ffa_init() and crb_acpi_driver_init(), modules.dep
takes care that they are loaded in order.

For IMA you will need the driver as built-in but that should
be handled via kernel config, not via code changes.

BR, Jarkko