linux-kernel - [PATCH] tpm, tpm_tis: Workaround failed command reception on Infineon devices

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Message-ID: <Z8lkSKOqBgt78pU2@earth.li>
Date: Thu, 6 Mar 2025 09:00:56 +0000
From: Jonathan McDowell <noodles@...th.li>
To: Jarkko Sakkinen <jarkko@...nel.org>, Peter Huewe <peterhuewe@....de>,
	Jason Gunthorpe <jgg@...pe.ca>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Stefan Berger <stefanb@...ux.ibm.com>
Cc: linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] tpm, tpm_tis: Workaround failed command reception on
 Infineon devices

From: Jonathan McDowell <noodles@...a.com>

Some Infineon devices have a issue where the status register will get
stuck with a quick REQUEST_USE / COMMAND_READY sequence. This is not
simply a matter of requiring a longer timeout; the work around is to
retry the command submission. Add appropriate logic to do this in the
send path.

This is fixed in later firmware revisions, but those are not always
available, and cannot generally be easily updated from outside a
firmware environment.

Testing has been performed with a simple repeated loop of doing a
TPM2_CC_GET_CAPABILITY for TPM_CAP_PROP_MANUFACTURER using the Go code
at:

 https://the.earth.li/~noodles/tpm-stuff/timeout-reproducer-simple.go

It can take several hours to reproduce, and millions of operations.

Signed-off-by: Jonathan McDowell <noodles@...a.com>
---
 drivers/char/tpm/tpm_tis_core.c | 17 ++++++++++++++---
 drivers/char/tpm/tpm_tis_core.h |  1 +
 include/linux/tpm.h             |  1 +
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 167d71747666..e4eae206a353 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -464,7 +464,10 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 
 		if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
 					&priv->int_queue, false) < 0) {
-			rc = -ETIME;
+			if (test_bit(TPM_TIS_STATUS_WORKAROUND, &priv->flags))
+				rc = -EAGAIN;
+			else
+				rc = -ETIME;
 			goto out_err;
 		}
 		status = tpm_tis_status(chip);
@@ -481,7 +484,10 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 
 	if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
 				&priv->int_queue, false) < 0) {
-		rc = -ETIME;
+		if (test_bit(TPM_TIS_STATUS_WORKAROUND, &priv->flags))
+			rc = -EAGAIN;
+		else
+			rc = -ETIME;
 		goto out_err;
 	}
 	status = tpm_tis_status(chip);
@@ -546,9 +552,11 @@ static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
 		if (rc >= 0)
 			/* Data transfer done successfully */
 			break;
-		else if (rc != -EIO)
+		else if (rc != EAGAIN && rc != -EIO)
 			/* Data transfer failed, not recoverable */
 			return rc;
+
+		usleep_range(priv->timeout_min, priv->timeout_max);
 	}
 
 	/* go and do it */
@@ -1144,6 +1152,9 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
 		priv->timeout_max = TIS_TIMEOUT_MAX_ATML;
 	}
 
+	if (priv->manufacturer_id == TPM_VID_IFX)
+		set_bit(TPM_TIS_STATUS_WORKAROUND, &priv->flags);
+
 	if (is_bsw()) {
 		priv->ilb_base_addr = ioremap(INTEL_LEGACY_BLK_BASE_ADDR,
 					ILB_REMAP_SIZE);
diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
index 690ad8e9b731..ce97b58dc005 100644
--- a/drivers/char/tpm/tpm_tis_core.h
+++ b/drivers/char/tpm/tpm_tis_core.h
@@ -89,6 +89,7 @@ enum tpm_tis_flags {
 	TPM_TIS_INVALID_STATUS		= 1,
 	TPM_TIS_DEFAULT_CANCELLATION	= 2,
 	TPM_TIS_IRQ_TESTED		= 3,
+	TPM_TIS_STATUS_WORKAROUND	= 4,
 };
 
 struct tpm_tis_data {
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 20a40ade8030..6c3125300c00 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -335,6 +335,7 @@ enum tpm2_cc_attrs {
 #define TPM_VID_WINBOND  0x1050
 #define TPM_VID_STM      0x104A
 #define TPM_VID_ATML     0x1114
+#define TPM_VID_IFX      0x15D1
 
 enum tpm_chip_flags {
 	TPM_CHIP_FLAG_BOOTSTRAPPED		= BIT(0),
-- 
2.48.1