[PATCH] tpm: Cache TPM2 start method

[Jarkko Sakkinen]

Both tpm_tis and tpm_crb have duplicate code for retrieving the start
method from TPM2 ACPI table. Eagerly cache the start method already at chip
creation. The cached chip->start_method can then be used by the leaf
drivers; or ignored depending on the requirements.

Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
---
 drivers/char/tpm/tpm-chip.c | 36 +++++++++++++++++++++++++++++-------
 include/linux/tpm.h         |  1 +
 2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 0be5dbfaa72e..540dd366effc 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -256,18 +256,24 @@ int tpm_class_shutdown(struct device *dev)
 }
 
 /**
- * tpm_chip_alloc() - allocate a new struct tpm_chip instance
- * @pdev: device to which the chip is associated
- *        At this point pdev mst be initialized, but does not have to
- *        be registered
- * @ops: struct tpm_class_ops instance
+ * tpm_chip_alloc() - Allocate a new struct tpm_chip instance
+ * @pdev:	device to which the chip is associated At this point pdev mst be
+ *		initialized, but does not have to be registered
+ * @ops:	struct tpm_class_ops for the chip.
+ *
+ * Allocates a new struct tpm_chip instance, and assigns a free device number
+ * for it. Must be paired with put_device(&chip->dev).
  *
- * Allocates a new struct tpm_chip instance and assigns a free
- * device number for it. Must be paired with put_device(&chip->dev).
+ * When ACPI is enabled, additionally tries to eagerly cache the start method
+ * from TPM2 ACPI table for the devices that need know it.
  */
 struct tpm_chip *tpm_chip_alloc(struct device *pdev,
 				const struct tpm_class_ops *ops)
 {
+#ifdef CONFIG_ACPI
+	struct acpi_table_tpm2 *tbl;
+	acpi_status status;
+#endif
 	struct tpm_chip *chip;
 	int rc;
 
@@ -275,6 +281,22 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
 	if (chip == NULL)
 		return ERR_PTR(-ENOMEM);
 
+#ifdef CONFIG_ACPI
+	chip->start_method = ACPI_TPM2_NOT_ALLOWED;
+	if (!acpi_disabled) {
+		status = acpi_get_table(ACPI_SIG_TPM2, 1, (struct acpi_table_header **)&tbl);
+		if (!ACPI_FAILURE(status) || tbl->header.length >= sizeof(*tbl)) {
+			chip->start_method = tbl->start_method;
+			dev_info(pdev, "TPM2 ACPI table is available");
+		} else {
+			dev_info(pdev, "TPM2 ACPI table is not available");
+		}
+
+		if (!ACPI_FAILURE(status))
+			acpi_put_table((struct acpi_table_header *)tbl);
+	}
+#endif
+
 	mutex_init(&chip->tpm_mutex);
 	init_rwsem(&chip->ops_sem);
 
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 0db277af45c3..f6cc91615469 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -149,6 +149,7 @@ struct tpm_chip {
 	struct tpm_bank_info allocated_banks[TPM2_MAX_PCR_BANKS];
 #ifdef CONFIG_ACPI
 	acpi_handle acpi_dev_handle;
+	u32 start_method;
 	char ppi_version[TPM_PPI_VERSION_LEN + 1];
 #endif /* CONFIG_ACPI */
 
-- 
2.47.3


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