[PATCH v2 3/4] tpm: reduce tpm_msleep() time in get_burstcount()

From: Nayna Jain <nayna@linux.vnet.ibm.com>
To: tpmdd-devel@lists.sourceforge.net
Cc: peterhuewe@gmx.de, tpmdd@selhorst.net,
	jarkko.sakkinen@linux.intel.com, jgunthorpe@obsidianresearch.com,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-ima-devel@lists.sourceforge.net, patrickc@us.ibm.com,
	Nayna Jain <nayna@linux.vnet.ibm.com>
Subject: [PATCH v2 3/4] tpm: reduce tpm_msleep() time in get_burstcount()
Date: Wed,  6 Sep 2017 08:56:38 -0400	[thread overview]
Message-ID: <20170906125643.5070-4-nayna@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170906125643.5070-1-nayna@linux.vnet.ibm.com>

Currently, get_burstcount() function sleeps for 5msec in a loop
before retrying for next query to burstcount. However, if it takes
lesser time for TPM to return, this 5 msec delay is longer
than necessary.

This patch replaces the tpm_msleep time from 5msec to 1msec.

After this change, performance on a TPM 1.2 with an 8 byte
burstcount for 1000 extends improved from ~10sec to ~9sec.

Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
 drivers/char/tpm/tpm_tis_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index d1eab29cb447..d710bbc4608b 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -169,7 +169,7 @@ static int get_burstcount(struct tpm_chip *chip)
 		burstcnt = (value >> 8) & 0xFFFF;
 		if (burstcnt)
 			return burstcnt;
-		tpm_msleep(TPM_TIMEOUT);
+		tpm_msleep(1);
 	} while (time_before(jiffies, stop));
 	return -EBUSY;
 }
-- 
2.13.3

