kernel/kernel-std/debian/patches/0009-tpm-ignore-burstcount-to-improve-tpm_tis-send-perfor.patch

From 451738188482a34603a184e868893f407998bdd4 Mon Sep 17 00:00:00 2001
From: Nayna Jain <nayna@linux.vnet.ibm.com>
Date: Fri, 10 Nov 2017 17:16:35 -0500
Subject: [PATCH 08/10] tpm: ignore burstcount to improve tpm_tis send()
 performance
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The TPM burstcount status indicates the number of bytes that can
be sent to the TPM without causing bus wait states.  Effectively,
it is the number of empty bytes in the command FIFO.

This patch optimizes the tpm_tis_send_data() function by checking
the burstcount only once. And if the burstcount is valid, it writes
all the bytes at once, permitting wait state.

After this change, performance on a TPM 1.2 with an 8 byte
burstcount for 1000 extends improved from ~41sec to ~14sec.

Suggested-by: Ken Goldman <kgold@linux.vnet.ibm.com> in
conjunction with the TPM Device Driver work group.
Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
Acked-by: Mimi Zohar <zohar@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>
Signed-off-by: Dongqi Chen <chen.dq@neusoft.com>
Signed-off-by: Jiping Ma <jiping.ma2@windriver.com>
---
 drivers/char/tpm/tpm_tis_core.c | 43 ++++++++++++---------------------
 1 file changed, 15 insertions(+), 28 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index a2e0395cbe61..2c69fde1e4e5 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -330,7 +330,6 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
 	int rc, status, burstcnt;
-	size_t count = 0;
 	bool itpm = priv->flags & TPM_TIS_ITPM_WORKAROUND;
 
 	status = tpm_tis_status(chip);
@@ -343,36 +342,24 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 			goto out_err;
 		}
 	}
-
-	while (count < len - 1) {
-		burstcnt = get_burstcount(chip);
-		if (burstcnt < 0) {
-			dev_err(&chip->dev, "Unable to read burstcount\n");
-			rc = burstcnt;
-			goto out_err;
-		}
-		burstcnt = min_t(int, burstcnt, len - count - 1);
-		rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality),
-					 burstcnt, buf + count);
-		if (rc < 0)
-			goto out_err;
-
-		count += burstcnt;
-
-		if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
-					&priv->int_queue, false) < 0) {
-			rc = -ETIME;
-			goto out_err;
-		}
-		status = tpm_tis_status(chip);
-		if (!itpm && (status & TPM_STS_DATA_EXPECT) == 0) {
-			rc = -EIO;
-			goto out_err;
-		}
+	/*
+	 * Get the initial burstcount to ensure TPM is ready to
+	 * accept data, even when waiting for burstcount is disabled.
+	 */
+	burstcnt = get_burstcount(chip);
+	if (burstcnt < 0) {
+		dev_err(&chip->dev, "Unable to read burstcount\n");
+		rc = burstcnt;
+		goto out_err;
 	}
 
+	rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality),
+					 len -1, buf);
+	if (rc < 0)
+		goto out_err;
+
 	/* write last byte */
-	rc = tpm_tis_write8(priv, TPM_DATA_FIFO(priv->locality), buf[count]);
+	rc = tpm_tis_write8(priv, TPM_DATA_FIFO(priv->locality), buf[len-1]);
 	if (rc < 0)
 		goto out_err;
 
-- 
2.29.2