From: Nayna Jain <nayna@linux.vnet.ibm.com>
Date: Tue, 17 Oct 2017 16:32:31 -0400
Subject: tpm: reduce tpm polling delay in tpm_tis_core
Git-commit: cf151a9a44d52a63332e8e926234574fe5a5d784
Patch-mainline: v4.16-rc1
References: FATE#326087

The existing wait_for_tpm_stat() polls for the chip status after
5msec sleep. As per TCG ddwg input, it is expected that tpm might
return status in few usec. So, reducing the delay in polling to
1msec.
Similarly, get_burstcount() function sleeps for 5msec before
retrying for next query to burstcount in a loop. If it takes
lesser time for TPM to return, this 5msec delay is longer than
necessary.

After this change, performance on a TPM 1.2 with an 8 byte
burstcount for 1000 extends improved from ~14sec to ~9sec.

Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Acked-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---
 drivers/char/tpm/tpm_tis_core.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 9e96b4b66aee..ca6b2b527d52 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -31,6 +31,12 @@
 #include "tpm.h"
 #include "tpm_tis_core.h"
 
+/* This is a polling delay to check for status and burstcount.
+ * As per ddwg input, expectation is that status check and burstcount
+ * check should return within few usecs.
+ */
+#define TPM_POLL_SLEEP	1  /* msec */
+
 static bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask,
 					bool check_cancel, bool *canceled)
 {
@@ -82,7 +88,7 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
 		}
 	} else {
 		do {
-			tpm_msleep(TPM_TIMEOUT);
+			tpm_msleep(TPM_POLL_SLEEP);
 			status = chip->ops->status(chip);
 			if ((status & mask) == mask)
 				return 0;
@@ -224,7 +230,7 @@ static int get_burstcount(struct tpm_chip *chip)
 		burstcnt = (value >> 8) & 0xFFFF;
 		if (burstcnt)
 			return burstcnt;
-		tpm_msleep(TPM_TIMEOUT);
+		tpm_msleep(TPM_POLL_SLEEP);
 	} while (time_before(jiffies, stop));
 	return -EBUSY;
 }