[PATCH RESEND v2 2/3] tpm2-cmd: Use dynamic delay to wait for self test result

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-d0qZbvYSIPpWk0Htik3J/[email protected]>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/[email protected]>
---
 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 8e940a5..2178437 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;
-- 
2.7.4


------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot