From 87434f58be31a96d72b5ddbb98d53307300e0024 Mon Sep 17 00:00:00 2001
From: Alexander Steffen <Alexander.Steffen@infineon.com>
Date: Thu, 31 Aug 2017 19:18:57 +0200
Subject: [PATCH] tpm: Use dynamic delay to wait for TPM 2.0 self test result

References: bsc#1082555
Patch-mainline: v4.15-rc1
Git-commit: 87434f58be31a96d72b5ddbb98d53307300e0024

In order to avoid delaying the code longer than necessary while still
giving the TPM enough time to execute the self tests asynchronously, start
with a small delay between two polls and increase it each round.

Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.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: Michal Suchanek <msuchanek@suse.de>
---
 drivers/char/tpm/tpm2-cmd.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 8e940a530df8..2178437e541a 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -877,20 +877,17 @@ static int tpm2_start_selftest(struct tpm_chip *chip, bool full)
 static int tpm2_do_selftest(struct tpm_chip *chip)
 {
 	int rc;
-	unsigned int loops;
-	unsigned int delay_msec = 100;
-	unsigned long duration;
-	int i;
-
-	duration = tpm2_calc_ordinal_duration(chip, TPM2_CC_SELF_TEST);
+	unsigned int delay_msec = 20;
+	long duration;
 
-	loops = jiffies_to_msecs(duration) / delay_msec;
+	duration = jiffies_to_msecs(
+		tpm2_calc_ordinal_duration(chip, TPM2_CC_SELF_TEST));
 
 	rc = tpm2_start_selftest(chip, false);
 	if (rc)
 		return rc;
 
-	for (i = 0; i < loops; i++) {
+	while (duration > 0) {
 		/* Attempt to read a PCR value */
 		rc = tpm2_pcr_read(chip, 0, NULL);
 		if (rc < 0)
@@ -900,6 +897,10 @@ static int tpm2_do_selftest(struct tpm_chip *chip)
 			break;
 
 		tpm_msleep(delay_msec);
+		duration -= delay_msec;
+
+		/* wait longer the next round */
+		delay_msec *= 2;
 	}
 
 	return rc;
-- 
2.13.7