linux-kernel - [PATCH 4/4] tpm_tis: Resend command to recover from data transfer errors

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Date:   Mon, 5 Jun 2023 19:52:50 +0200
From:   Alexander Steffen <Alexander.Steffen@...ineon.com>
To:     <jarkko@...nel.org>, <linux-integrity@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Alexander Steffen <Alexander.Steffen@...ineon.com>
Subject: [PATCH 4/4] tpm_tis: Resend command to recover from data transfer errors

Similar to the transmission of TPM responses, also the transmission of TPM
commands may become corrupted. Instead of aborting when detecting such
issues, try resending the command again.

Change-Id: Ifad9cccff94b59242d36fba9c1e92c7a6bb57804
Signed-off-by: Alexander Steffen <Alexander.Steffen@...ineon.com>
---
 drivers/char/tpm/tpm_tis_core.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index a08768e55803..47073cc79b51 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -535,10 +535,18 @@ static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
 	int rc;
 	u32 ordinal;
 	unsigned long dur;
+	unsigned int try;
 
-	rc = tpm_tis_send_data(chip, buf, len);
-	if (rc < 0)
-		return rc;
+	for (try = 0; try < TPM_RETRY; try++) {
+		rc = tpm_tis_send_data(chip, buf, len);
+		if (rc >= 0) {
+			/* Data transfer done successfully */
+			break;
+		} else if (rc != -EIO) {
+			/* Data transfer failed, not recoverable */
+			return rc;
+		}
+	}
 
 	/* go and do it */
 	rc = tpm_tis_write8(priv, TPM_STS(priv->locality), TPM_STS_GO);
-- 
2.34.1