tpm: Add upgrade/reduced mode support for TPM1.2 modules

In case a TPM in failure mode is detected, the TPM should be accessible
through a transparent communication channel for analysing purposes (e.g.
TPM_GetTestResult) or a field upgrade. Since a TPM in failure mode has
similar reduced functionality as in field upgrade mode, the flag
TPM_CHIP_FLAG_FIRMWARE_UPGRADE is also valid.

As described in TCG TPM Main Part1 Design Principles, Revision 116,
chapter 9.2.1. the TPM also allows an update function in case a TPM is
in failure mode.

If the TPM in failure mode is detected, the function tpm1_auto_startup()
sets TPM_CHIP_FLAG_FIRMWARE_UPGRADE flag, which is used later during
driver initialization/deinitialization to disable functionality which
makes no sense or will fail in the current TPM state. The following
functionality is affected:
* Do not register TPM as a hwrng
* Do not get pcr allocation
* Do not register sysfs entries which provide information impossible to
obtain in limited mode

Signed-off-by: Stefan Mahnke-Hartmann <[e-mail]>
Reviewed-by: Jarkko Sakkinen <[e-mail]>
Signed-off-by: Jarkko Sakkinen <[e-mail]>

drivers/char/tpm/tpm.h

···
 #define TPM_WARN_DOING_SELFTEST 0x802
 #define TPM_ERR_DEACTIVATED     0x6
 #define TPM_ERR_DISABLED        0x7
+#define TPM_ERR_FAILEDSELFTEST  0x1C
 #define TPM_ERR_INVALID_POSTINIT 38
 
 #define TPM_TAG_RQU_COMMAND 193

drivers/char/tpm/tpm1-cmd.c

···
 	if (rc)
 		goto out;
 	rc = tpm1_do_selftest(chip);
-	if (rc) {
+	if (rc == TPM_ERR_FAILEDSELFTEST) {
+		dev_warn(&chip->dev, "TPM self test failed, switching to the firmware upgrade mode\n");
+		/* A TPM in this state possibly allows or needs a firmware upgrade */
+		chip->flags |= TPM_CHIP_FLAG_FIRMWARE_UPGRADE;
+		return 0;
+	} else if (rc) {
 		dev_err(&chip->dev, "TPM self test failed\n");
 		goto out;
 	}