[PATCH] tpm_tis_core: Choose appropriate timeout for reading burstcount

From: Peter Huewe
Date: Thu Feb 16 2017 - 10:44:14 EST

From: Alexander Steffen <Alexander.Steffen@xxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx
Fixes: aec04cbdf723 ("tpm: TPM 2.0 FIFO Interface")

Signed-off-by: Alexander Steffen <Alexander.Steffen@xxxxxxxxxxxx>
Signed-off-by: Peter Huewe <peter.huewe@xxxxxxxxxxxx>
drivers/char/tpm/tpm_tis_core.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index c0f296b5d413..fc0e9a2734ed 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -160,8 +160,10 @@ static int get_burstcount(struct tpm_chip *chip)
u32 value;

/* wait for burstcount */
- /* which timeout value, spec has 2 answers (c & d) */
- stop = jiffies + chip->timeout_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);
if (rc < 0)