[RFC PATCH] tpm: Workaround failed command reception on Infineon devices

[Jonathan McDowell <noodles@earth.li>]

(I'm still in the process of testing this to confirm it fixes the
errata I've seen, but I wanted to send it out for comments to make sure
it's a reasonable approach.)

Some Infineon devices have a issue where the status register will get
stuck with a quick REQUEST_USE / COMMAND_READY sequence. The work around
is to retry the command submission. Add appropriate logic to do this in
the send path.

Signed-off-by: Jonathan McDowell <noodles@meta.com>
---
 drivers/char/tpm/tpm_tis_core.c | 24 +++++++++++++++++++-----
 drivers/char/tpm/tpm_tis_core.h |  1 +
 include/linux/tpm.h             |  1 +
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index f6aa0dfadb93..940abd1a868e 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -432,16 +432,27 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
-	int rc, status, burstcnt;
+	int rc, status, burstcnt, retry;
+	bool status_fix = test_bit(TPM_TIS_STATUS_WORKAROUND, &priv->flags);
 	size_t count = 0;
 	bool itpm = test_bit(TPM_TIS_ITPM_WORKAROUND, &priv->flags);
 
 	status = tpm_tis_status(chip);
 	if ((status & TPM_STS_COMMAND_READY) == 0) {
-		tpm_tis_ready(chip);
-		if (wait_for_tpm_stat
-		    (chip, TPM_STS_COMMAND_READY, chip->timeout_b,
-		     &priv->int_queue, false) < 0) {
+		retry = status_fix ? 3 : 1;
+
+		while (retry > 0) {
+			tpm_tis_ready(chip);
+			if (wait_for_tpm_stat
+			    (chip, TPM_STS_COMMAND_READY, chip->timeout_b,
+			     &priv->int_queue, false) >= 0) {
+				break;
+			}
+
+			retry--;
+		}
+
+		if (retry == 0) {
 			rc = -ETIME;
 			goto out_err;
 		}
@@ -1147,6 +1158,9 @@ 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 13e99cf65efe..f888da57535d 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 4ee9d13749ad..5f4998626a98 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -272,6 +272,7 @@ 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),
-- 
2.39.5