[PATCH linux dev-5.8 3/9] tpm: tpm_tis: Add retry in case of protocol failure.

[Klaus Heinrich Kiwi]

From: Amir Mizinski <amirmizi6 at gmail.com>

Added a retry mechanism on any protocol error when sending a command or
receiving a response. This was changed to comply with
the TCG PC Client Device Driver Design Principles for TPM 2.0.

When sending a command, a loop is added in "tpm_tis_send_main()" that calls
"tpm_tis_send_data()" and then issues a retry attempt if any error occurs.
When receiving a response, the following new function derived from
"tpm_tis_recv()" is added: "__tpm_tis_recv()". "tpm_tis_recv()" is modified
to call "__tpm_tis_recv()" in a loop. If any error occurs, a retry is
initiated by setting TPM_STS.responseRetry and "__tpm_tis_recv()" is
called again.
In both cases a retry is attempted up to "TPM_RETRY" times.

Co-developed-by: Christophe Ricard <christophe-h.ricard at st.com>
Signed-off-by: Christophe Ricard <christophe-h.ricard at st.com>
Signed-off-by: Amir Mizinski <amirmizi6 at gmail.com>
---
 drivers/char/tpm/tpm_tis_core.c | 62 +++++++++++++++++++++------------
 drivers/char/tpm/tpm_tis_core.h |  1 +
 2 files changed, 41 insertions(+), 22 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 83004fcc93ff..931240674579 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -305,29 +305,24 @@ static int recv_data(struct tpm_chip *chip, u8 *buf, size_t count)
 	return size;
 }
 
-static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
+static int __tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
 	int size = 0;
 	int status;
 	u32 expected;
 
-	if (count < TPM_HEADER_SIZE) {
-		size = -EIO;
-		goto out;
-	}
-
 	size = recv_data(chip, buf, TPM_HEADER_SIZE);
 	/* read first 10 bytes, including tag, paramsize, and result */
 	if (size < TPM_HEADER_SIZE) {
 		dev_err(&chip->dev, "Unable to read header\n");
-		goto out;
+		return size;
 	}
 
 	expected = be32_to_cpu(*(__be32 *) (buf + 2));
 	if (expected > count || expected < TPM_HEADER_SIZE) {
 		size = -EIO;
-		goto out;
+		return size;
 	}
 
 	size += recv_data(chip, &buf[TPM_HEADER_SIZE],
@@ -335,22 +330,45 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 	if (size < expected) {
 		dev_err(&chip->dev, "Unable to read remainder of result\n");
 		size = -ETIME;
-		goto out;
+		return size;
 	}
 
 	if (tpm_tis_wait_for_stat(chip, TPM_STS_VALID, TPM_STS_VALID,
 				  chip->timeout_c, &priv->int_queue,
 				  false) < 0) {
 		size = -ETIME;
-		goto out;
+		return size;
 	}
+
 	status = tpm_tis_status(chip);
 	if (status & TPM_STS_DATA_AVAIL) {	/* retry? */
 		dev_err(&chip->dev, "Error left over data\n");
+		size = -EIO;
+		return size;
+	}
+
+	return size;
+}
+
+static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
+{
+	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
+	int size;
+	int i;
+
+	if (count < TPM_HEADER_SIZE) {
 		size = -EIO;
 		goto out;
 	}
 
+	for (i = 0; i < TPM_RETRY; i++) {
+		size = __tpm_tis_recv(chip, buf, count);
+		if (size <= 0)
+			tpm_tis_write8(priv, TPM_STS(priv->locality),
+				       TPM_STS_RESPONSE_RETRY);
+		else
+			goto out;
+	}
 out:
 	tpm_tis_ready(chip);
 	return size;
@@ -375,7 +393,7 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 					  chip->timeout_b, &priv->int_queue,
 					  false) < 0) {
 			rc = -ETIME;
-			goto out_err;
+			return rc;
 		}
 	}
 
@@ -384,13 +402,13 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 		if (burstcnt < 0) {
 			dev_err(&chip->dev, "Unable to read burstcount\n");
 			rc = burstcnt;
-			goto out_err;
+			return rc;
 		}
 		burstcnt = min_t(int, burstcnt, len - count);
 		rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality),
 					 burstcnt, buf + count);
 		if (rc < 0)
-			goto out_err;
+			return rc;
 
 		count += burstcnt;
 	}
@@ -398,14 +416,10 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 				  TPM_STS_VALID, chip->timeout_a,
 				  &priv->int_queue, false) < 0) {
 		rc = -ETIME;
-		goto out_err;
+		return rc;
 	}
 
 	return 0;
-
-out_err:
-	tpm_tis_ready(chip);
-	return rc;
 }
 
 static void disable_interrupts(struct tpm_chip *chip)
@@ -437,13 +451,17 @@ static void disable_interrupts(struct tpm_chip *chip)
 static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
-	int rc;
+	int rc, i;
 	u32 ordinal;
 	unsigned long dur;
 
-	rc = tpm_tis_send_data(chip, buf, len);
-	if (rc < 0)
-		return rc;
+	for (i = 0; i < TPM_RETRY; i++) {
+		rc = tpm_tis_send_data(chip, buf, len);
+		if (rc >= 0)
+			break;
+	}
+	if (i == TPM_RETRY)
+		goto out_err;
 
 	/* go and do it */
 	rc = tpm_tis_write8(priv, TPM_STS(priv->locality), TPM_STS_GO);
diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
index d06c65b63cf5..6cc6b761a095 100644
--- a/drivers/char/tpm/tpm_tis_core.h
+++ b/drivers/char/tpm/tpm_tis_core.h
@@ -34,6 +34,7 @@ enum tis_status {
 	TPM_STS_GO = 0x20,
 	TPM_STS_DATA_AVAIL = 0x10,
 	TPM_STS_DATA_EXPECT = 0x08,
+	TPM_STS_RESPONSE_RETRY = 0x02,
 };
 
 enum tis_int_flags {
-- 
2.20.1