tpm: work around bug in Broadcom BCM0102 chipset

Patch tpm-correct-tpm-timeouts-to-jiffies-conversion reveals a bug in the
Broadcom BCM0102 TPM chipset used in the Dell Latitude D820 - although
most of the timeouts are returned in usecs as per the spec, one is
apparently returned in msecs, which results in a too-small value leading
to a timeout when the code treats it as usecs.  To prevent a regression,
we check for the known too-short value and adjust it to a value that makes
things work.

Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Cc: Marcin Obara <marcin_obara@users.sourceforge.net>
Cc: Marcel Selhorst <tpm@selhorst.net>
Cc: Kylene Jo Hall <kjhall@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index 6b5a0e0127a7..aa899cec6b3f 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -557,6 +557,13 @@ duration:
             usecs_to_jiffies(be32_to_cpu
                              (*((__be32 *) (data +
                                             TPM_GET_CAP_RET_UINT32_1_IDX))));
+        /* The Broadcom BCM0102 chipset in a Dell Latitude D820 gets the above
+         * value wrong and apparently reports msecs rather than usecs. So we
+         * fix up the resulting too-small TPM_SHORT value to make things work.
+         */
+        if (chip->vendor.duration[TPM_SHORT] < (HZ/100))
+                chip->vendor.duration[TPM_SHORT] = HZ;
+
         chip->vendor.duration[TPM_MEDIUM] =
             usecs_to_jiffies(be32_to_cpu
                              (*((__be32 *) (data +