linux-kernel - [PATCH 2/2] tpm: add sleep only for retry in i2c_nuvoton_write

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Date:   Fri, 10 Mar 2017 13:45:54 -0500
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,
        dan.morav@...oton.com, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Nayna Jain <nayna@...ux.vnet.ibm.com>,
        stable@...r.kernel.org (linux-4.8)
Subject: [PATCH 2/2] tpm: add sleep only for retry in i2c_nuvoton_write_status()

Currently, there is an unnecessary 1 msec delay added in
i2c_nuvoton_write_status() for the successful case. This 
function is called multiple times during send() and recv(),
which implies adding multiple extra delays for every TPM
operation.

This patch calls usleep_range() only if retry is to be done.

Signed-off-by: Nayna Jain <nayna@...ux.vnet.ibm.com>
Cc: stable@...r.kernel.org (linux-4.8)
Reviewed-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
---
 drivers/char/tpm/tpm_i2c_nuvoton.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm_i2c_nuvoton.c b/drivers/char/tpm/tpm_i2c_nuvoton.c
index 0c98c42..c642877 100644
--- a/drivers/char/tpm/tpm_i2c_nuvoton.c
+++ b/drivers/char/tpm/tpm_i2c_nuvoton.c
@@ -124,8 +124,9 @@ static s32 i2c_nuvoton_write_status(struct i2c_client *client, u8 data)
 	/* this causes the current command to be aborted */
 	for (i = 0, status = -1; i < TPM_I2C_RETRY_COUNT && status < 0; i++) {
 		status = i2c_nuvoton_write_buf(client, TPM_STS, 1, &data);
-		usleep_range(TPM_I2C_BUS_DELAY, TPM_I2C_BUS_DELAY
-			     + TPM_I2C_DELAY_RANGE);
+		if (status < 0)
+			usleep_range(TPM_I2C_BUS_DELAY, TPM_I2C_BUS_DELAY
+				     + TPM_I2C_DELAY_RANGE);
 	}
 	return status;
 }
-- 
2.9.3