From: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Date: Wed, 24 May 2023 17:40:39 +0200
Subject: [PATCH] tpm: tis_i2c: Limit read bursts to I2C_SMBUS_BLOCK_MAX (32)
 bytes
References: bsc#1012628
Patch-mainline: 6.4.5
Git-commit: f3b70b6e3390bfdf18fdd7d278a72a12784fdcce

commit f3b70b6e3390bfdf18fdd7d278a72a12784fdcce upstream.

Underlying I2C bus drivers not always support longer transfers and
imx-lpi2c for instance doesn't. SLB 9673 offers 427-bytes packets.

Visible symptoms are:

tpm tpm0: Error left over data
tpm tpm0: tpm_transmit: tpm_recv: error -5
tpm_tis_i2c: probe of 1-002e failed with error -5

Cc: stable@vger.kernel.org # v5.20+
Fixes: bbc23a07b072 ("tpm: Add tpm_tis_i2c backend for tpm_tis_core")
Tested-by: Michael Haener <michael.haener@siemens.com>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/char/tpm/tpm_tis_i2c.c | 37 ++++++++++++++++++++--------------
 1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_i2c.c b/drivers/char/tpm/tpm_tis_i2c.c
index c8c34adc..106fd20d 100644
--- a/drivers/char/tpm/tpm_tis_i2c.c
+++ b/drivers/char/tpm/tpm_tis_i2c.c
@@ -189,21 +189,28 @@ static int tpm_tis_i2c_read_bytes(struct tpm_tis_data *data, u32 addr, u16 len,
 	int ret;
 
 	for (i = 0; i < TPM_RETRY; i++) {
-		/* write register */
-		msg.len = sizeof(reg);
-		msg.buf = &reg;
-		msg.flags = 0;
-		ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
-		if (ret < 0)
-			return ret;
-
-		/* read data */
-		msg.buf = result;
-		msg.len = len;
-		msg.flags = I2C_M_RD;
-		ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
-		if (ret < 0)
-			return ret;
+		u16 read = 0;
+
+		while (read < len) {
+			/* write register */
+			msg.len = sizeof(reg);
+			msg.buf = &reg;
+			msg.flags = 0;
+			ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
+			if (ret < 0)
+				return ret;
+
+			/* read data */
+			msg.buf = result + read;
+			msg.len = len - read;
+			msg.flags = I2C_M_RD;
+			if (msg.len > I2C_SMBUS_BLOCK_MAX)
+				msg.len = I2C_SMBUS_BLOCK_MAX;
+			ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
+			if (ret < 0)
+				return ret;
+			read += msg.len;
+		}
 
 		ret = tpm_tis_i2c_sanity_check_read(reg, len, result);
 		if (ret == 0)
-- 
2.35.3