linux-kernel - [PATCH v2 3/4] tpm: reduce tpm_msleep() time in get

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Date:   Wed,  6 Sep 2017 08:56:38 -0400
From:   Nayna Jain <nayna@...ux.vnet.ibm.com>
To:     tpmdd-devel@...ts.sourceforge.net
Cc:     peterhuewe@....de, tpmdd@...horst.net,
        jarkko.sakkinen@...ux.intel.com, jgunthorpe@...idianresearch.com,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-ima-devel@...ts.sourceforge.net, patrickc@...ibm.com,
        Nayna Jain <nayna@...ux.vnet.ibm.com>
Subject: [PATCH v2 3/4] tpm: reduce tpm_msleep() time in get_burstcount()

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@...ux.vnet.ibm.com>
Acked-by: Mimi Zohar <zohar@...ux.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