tpm: Use dynamic delay to wait for TPM 2.0 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 <[email protected]> Reviewed-by: Jarkko Sakkinen <[email protected]> Tested-by: Jarkko Sakkinen <[email protected]> Signed-off-by: Jarkko Sakkinen <[email protected]>
MaxKrummenacher · Oct 18, 2017 · 87434f5 · 87434f5
1 parent 2482b1b
commit 87434f5
Showing 1 changed file with 9 additions and 8 deletions.
diff --git 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;