[PATCH v3 2/2] tpm: tpm_tis: Add settle time for some TPMs

[Jim Broadus <jbroadus@gmail.com>]

Some TPMs fail to grant locality when requested immediately after being
relinquished. In this case, the TPM_ACCESS_REQUEST_USE bit of the
TPM_ACCESS register is cleared immediately without setting
TPM_ACCESS_ACTIVE_LOCALITY.

This issue can be seen at boot since tpm_chip_start, called right
after locality is relinquished, will fail. This causes the probe to
fail:

tpm_tis MSFT0101:00: probe with driver tpm_tis failed with error -1

This occurs on some older Dell Latitudes. For the Nuvoton TPM used in
these machines, add a delay after locality is relinquished.

Signed-off-by: Jim Broadus <jbroadus@gmail.com>
---
 drivers/char/tpm/tpm_tis_core.c | 6 ++++++
 drivers/char/tpm/tpm_tis_core.h | 1 +
 2 files changed, 7 insertions(+)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index d0b87f5daa3e..e0ee98e93ede 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -171,6 +171,9 @@ static int __tpm_tis_relinquish_locality(struct tpm_tis_data *priv, int l)
 {
 	tpm_tis_write8(priv, TPM_ACCESS(l), TPM_ACCESS_ACTIVE_LOCALITY);
 
+	if (test_bit(TPM_TIS_SETTLE_AFTER_RELINQUISH, &priv->flags))
+		tpm_msleep(TPM_TIMEOUT);
+
 	return 0;
 }
 
@@ -1166,6 +1169,9 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
 	if (vendor_id == TPM_VID_IFX)
 		set_bit(TPM_TIS_STATUS_VALID_RETRY, &priv->flags);
 
+	if (vendor_id == TPM_VID_WINBOND && device_id == 0x00FE)
+		set_bit(TPM_TIS_SETTLE_AFTER_RELINQUISH, &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 f2c77844062a..aa6d78898ef3 100644
--- a/drivers/char/tpm/tpm_tis_core.h
+++ b/drivers/char/tpm/tpm_tis_core.h
@@ -90,6 +90,7 @@ enum tpm_tis_flags {
 	TPM_TIS_DEFAULT_CANCELLATION	= 2,
 	TPM_TIS_IRQ_TESTED		= 3,
 	TPM_TIS_STATUS_VALID_RETRY	= 4,
+	TPM_TIS_SETTLE_AFTER_RELINQUISH	= 5,
 };
 
 struct tpm_tis_data {
-- 
2.54.0