tpm_tis_core: Choose appropriate timeout for reading burstcount

TIS v1.3 for TPM 1.2 and PTP for TPM 2.0 disagree about which timeout
value applies to reading a valid burstcount. It is TIMEOUT_D according to
TIS, but TIMEOUT_A according to PTP, so choose the appropriate value
depending on whether we deal with a TPM 1.2 or a TPM 2.0.

This is important since according to the PTP TIMEOUT_D is much smaller
than TIMEOUT_A. So the previous implementation could run into timeouts
with a TPM 2.0, even though the TPM was behaving perfectly fine.

During tpm2_probe TIMEOUT_D will be used even with a TPM 2.0, because
TPM_CHIP_FLAG_TPM2 is not yet set. This is fine, since the timeout values
will only be changed afterwards by tpm_get_timeouts. Until then
TIS_TIMEOUT_D_MAX applies, which is large enough.

Cc: stable@vger.kernel.org
Fixes: aec04cbd ("tpm: TPM 2.0 FIFO Interface")
Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com>
Signed-off-by: Peter Huewe <peter.huewe@infineon.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

drivers/char/tpm/tpm_tis_core.c

@@ -160,7 +160,9 @@ static int get_burstcount(struct tpm_chip *chip)
 	u32 value;
 
 	/* wait for burstcount */
-	/* which timeout value, spec has 2 answers (c & d) */
+	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+		stop = jiffies + chip->timeout_a;
+	else
 		stop = jiffies + chip->timeout_d;
 	do {
 		rc = tpm_tis_read32(priv, TPM_STS(priv->locality), &value);