tcti-spi-helper does not tell the TPM to become ready

[Akuli]

According to this spec I found, when the TPM is started it can be initially in ready or idle state.

If it happens to stay in idle state, tcti-spi-helper will fail here:

tpm2-tss/src/tss2-tcti/tcti-spi-helper.c

Lines 739 to 747 in 86949f7

	// Wait up to 200ms for TPM to become ready
	LOG_DEBUG("Waiting for TPM to become ready...");
	uint32_t expected_status_bits = TCTI_SPI_HELPER_TPM_STS_COMMAND_READY;
	rc = spi_tpm_helper_wait_for_status(ctx, expected_status_bits, expected_status_bits, 200);
	if (rc != TSS2_RC_SUCCESS) {
	LOG_ERROR("Failed waiting for TPM to become ready");
	return rc;
	}
	LOG_DEBUG("TPM is ready");

This makes tcti-spi-helper unusable in the project I am working on now.

A quick and dirty fix is to just ask the TPM chip to transition to ready state and try again:

diff --git a/src/tss2-tcti/tcti-spi-helper.c b/src/tss2-tcti/tcti-spi-helper.c
index 515a5363..f2d69c0f 100644
--- a/src/tss2-tcti/tcti-spi-helper.c
+++ b/src/tss2-tcti/tcti-spi-helper.c
@@ -740,6 +740,10 @@ TSS2_RC Tss2_Tcti_Spi_Helper_Init (TSS2_TCTI_CONTEXT* tcti_context, size_t* size
     LOG_DEBUG("Waiting for TPM to become ready...");
     uint32_t expected_status_bits = TCTI_SPI_HELPER_TPM_STS_COMMAND_READY;
     rc = spi_tpm_helper_wait_for_status(ctx, expected_status_bits, expected_status_bits, 200);
+    if (rc != TSS2_RC_SUCCESS) {
+        spi_tpm_helper_write_sts_reg(ctx, TCTI_SPI_HELPER_TPM_STS_COMMAND_READY);
+        rc = spi_tpm_helper_wait_for_status(ctx, expected_status_bits, expected_status_bits, 200);
+    }
     if (rc != TSS2_RC_SUCCESS) {
         LOG_ERROR("Failed waiting for TPM to become ready");
         return rc;