[PATCH v2 1/4] tpm: Cache TPM2 start method

[Siddharth Chintamaneni <sidchintamaneni@gmail.com>]

From: Jarkko Sakkinen <jarkko@kernel.org>

Both tpm_tis and tpm_crb retrieve the start method from the ACPI TPM2
table during device probe, and tpm_crb_ffa also needs it before chip
allocation.

Cache the start method in tpm2_acpi_start_method during tpm_init() and
export it for the leaf drivers, defaulting to ACPI_TPM2_NOT_ALLOWED when
the table is absent or invalid.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Co-developed-by: Siddharth Chintamaneni <sidchintamaneni@gmail.com>
Signed-off-by: Siddharth Chintamaneni <sidchintamaneni@gmail.com>
---
 drivers/char/tpm/tpm-interface.c | 21 +++++++++++++++++++++
 drivers/char/tpm/tpm.h           |  1 +
 2 files changed, 22 insertions(+)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index e0385b16616b..7b7da79bee7c 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -534,8 +534,17 @@ int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max)
 }
 EXPORT_SYMBOL_GPL(tpm_get_random);
 
+#ifdef CONFIG_ACPI
+u32 tpm2_acpi_start_method = ACPI_TPM2_NOT_ALLOWED;
+EXPORT_SYMBOL_GPL(tpm2_acpi_start_method);
+#endif
+
 static int __init tpm_init(void)
 {
+#ifdef CONFIG_ACPI
+	struct acpi_table_tpm2 *tbl;
+	acpi_status status;
+#endif
 	int rc;
 
 	rc = class_register(&tpm_class);
@@ -562,6 +571,18 @@ static int __init tpm_init(void)
 		goto out_unreg_chrdev;
 	}
 
+#ifdef CONFIG_ACPI
+	if (!acpi_disabled) {
+		status = acpi_get_table(ACPI_SIG_TPM2, 1,
+					(struct acpi_table_header **)&tbl);
+		if (ACPI_SUCCESS(status)) {
+			if (tbl->header.length >= sizeof(*tbl))
+				tpm2_acpi_start_method = tbl->start_method;
+			acpi_put_table((struct acpi_table_header *)tbl);
+		}
+	}
+#endif
+
 	return 0;
 
 out_unreg_chrdev:
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index fa554c5ad80b..212ca2410c93 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -100,6 +100,7 @@ void tpm_sysfs_add_device(struct tpm_chip *chip);
 
 
 #ifdef CONFIG_ACPI
+extern u32 tpm2_acpi_start_method;
 extern void tpm_add_ppi(struct tpm_chip *chip);
 #else
 static inline void tpm_add_ppi(struct tpm_chip *chip)
-- 
2.45.4