tpm, tpm_tis: fix TPM 2.0 probing

If during transmission system error was returned, the logic was to
incorrectly deduce that chip is a TPM 1.x chip. This patch fixes this
issue. Also, this patch changes probing so that message tag is used as the
measure for TPM 2.x, which should be much more stable. A separate function
called tpm2_probe() is encapsulated because it can be used with any
chipset.

Fixes: aec04cbdf7 ("tpm: TPM 2.0 FIFO Interface")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Peter Huewe <peterhuewe@gmx.de>

drivers/char/tpm/tpm2-cmd.c

@@ -601,20 +601,46 @@ EXPORT_SYMBOL_GPL(tpm2_do_selftest);
 /**
  * tpm2_gen_interrupt() - generate an interrupt
  * @chip: TPM chip to use
- * @quiet: surpress the error message
  *
  * 0 is returned when the operation is successful. If a negative number is
  * returned it remarks a POSIX error code. If a positive number is returned
  * it remarks a TPM error.
  */
-int tpm2_gen_interrupt(struct tpm_chip *chip, bool quiet)
+int tpm2_gen_interrupt(struct tpm_chip *chip)
 {
-	const char *desc = NULL;
 	u32 dummy;
 
-	if (!quiet)
-		desc = "attempting to generate an interrupt";
-
-	return tpm2_get_tpm_pt(chip, TPM2_CAP_TPM_PROPERTIES, &dummy, desc);
+	return tpm2_get_tpm_pt(chip, 0x100, &dummy,
+			       "attempting to generate an interrupt");
 }
 EXPORT_SYMBOL_GPL(tpm2_gen_interrupt);
+
+/**
+ * tpm2_probe() - probe TPM 2.0
+ * @chip: TPM chip to use
+ *
+ * Send idempotent TPM 2.0 command and see whether TPM 2.0 chip replied based on
+ * the reply tag.
+ */
+int tpm2_probe(struct tpm_chip *chip)
+{
+	struct tpm2_cmd cmd;
+	int rc;
+
+	cmd.header.in = tpm2_get_tpm_pt_header;
+	cmd.params.get_tpm_pt_in.cap_id = cpu_to_be32(TPM2_CAP_TPM_PROPERTIES);
+	cmd.params.get_tpm_pt_in.property_id = cpu_to_be32(0x100);
+	cmd.params.get_tpm_pt_in.property_cnt = cpu_to_be32(1);
+
+	rc = tpm_transmit(chip, (const char *) &cmd, sizeof(cmd));
+	if (rc <  0)
+		return rc;
+	else if (rc < TPM_HEADER_SIZE)
+		return -EFAULT;
+
+	if (be16_to_cpu(cmd.header.out.tag) == TPM2_ST_NO_SESSIONS)
+		chip->flags |= TPM_CHIP_FLAG_TPM2;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tpm2_probe);