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tpm: fix intermittent failure with self tests
My Nuvoton 6xx in a Dell XPS-13 has been intermittently failing to work (necessitating a reboot). The problem seems to be that the TPM gets into a state where the partial self-test doesn't return TPM_RC_SUCCESS (meaning all tests have run to completion), but instead returns TPM_RC_TESTING (meaning some tests are still running in the background). There are various theories that resending the self-test command actually causes the tests to restart and thus triggers more TPM_RC_TESTING returns until the timeout is exceeded. There are several issues here: firstly being we shouldn't slow down the boot sequence waiting for the self test to complete once the TPM backgrounds them. It will actually make available all functions that have passed and if it gets a failure return TPM_RC_FAILURE to every subsequent command. So the fix is to kick off self tests once and if they return TPM_RC_TESTING log that as a backgrounded self test and continue on. In order to prevent other tpm users from seeing any TPM_RC_TESTING returns (which it might if they send a command that needs a TPM subsystem which is still under test), we loop in tpm_transmit_cmd until either a timeout or we don't get a TPM_RC_TESTING return. Finally, there have been observations of strange returns from a partial test. One Nuvoton is occasionally returning TPM_RC_COMMAND_CODE, so treat any unexpected return from a partial self test as an indication we need to run a full self test. [jarkko.sakkinen@linux.intel.com: cleaned up some klog messages and dropped tpm_transmit_check() helper function from James' original commit.] Fixes: 2482b1bb ("tpm: Trigger only missing TPM 2.0 self tests") Cc: stable@vger.kernel.org Signed-off-by:James Bottomley <James.Bottomley@HansenPartnership.com> Reviewed-by: