[PATCH 1/1] Fix TPM chip hanging system before suspend/shutdown

[Adam Alves <adamoa@gmail.com>]

My PC would hang on almost every shutdown/suspend until I started
testing this patch and so far in the past week I haven’t experienced
any problems anymore.

I suspect that the root cause on my specific board is that after the
ACPI command to put the device to S3 or S5, some firmware
application/driver will try to use the TPM chip expecting it to be in
Locality 0 as expected by TCG PC Client Platform Firmware Profile
Version 1.06 Revision 52 (3.1.1 – Pre-OS Environment) and then when it
fails to do so it simply halts the whole system.

This issue might be related to the following bug:
https://bugzilla.kernel.org/show_bug.cgi?id=217890

Enable a user to configure the kernel
through “tpm.locality_on_suspend=1” boot parameter so that the locality
is set before suspend/shutdown in order to diagnose whether or not the
board is one of the buggy ones that require this workaround. Since this
bug is related to the board/platform instead of the specific TPM chip,
call dmi_check_system on the tpm_init function so that this setting is
automatically enabled for boards specified in code (ASUS TUF GAMING
B460M-PLUS already included) – automatic configuration only works in
case CONFIG_DMI is set though, since dmi_check_system is a non-op when
CONFIG_DMI is not set.

In case “tpm.locality_on_suspend=0” (the default) don't change any
behavior thus preserving current functionality of any other board
except ASUSTeK COMPUTER INC. TUF GAMING B460M-PLUS and possibly future
boards as we successfully diagnose other boards with the same issue
fixed by using “tpm.locality_on_suspend=1”.

Signed-off-by: Adam Alves <adamoa@gmail.com>
---
 drivers/char/tpm/tpm-chip.c      |  9 ++++++++
 drivers/char/tpm/tpm-interface.c | 36 +++++++++++++++++++++++++++++++-
 drivers/char/tpm/tpm.h           |  1 +
 include/linux/tpm.h              |  1 +
 4 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 42b1062e33cd..8fdf7a137a94 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -139,6 +139,9 @@ void tpm_chip_stop(struct tpm_chip *chip)
 {
 	tpm_go_idle(chip);
 	tpm_relinquish_locality(chip);
+	// If locality is to be preserved, we need to make sure it is Locality 0.
+	if (chip->flags & TPM_CHIP_PRESERVE_LOCALITY)
+		tpm_request_locality(chip);
 	tpm_clk_disable(chip);
 }
 EXPORT_SYMBOL_GPL(tpm_chip_stop);
@@ -291,6 +294,9 @@ int tpm_class_shutdown(struct device *dev)
 {
 	struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);
 
+	if (tpm_locality_on_suspend)
+		chip->flags |= TPM_CHIP_PRESERVE_LOCALITY;
+
 	down_write(&chip->ops_sem);
 	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
 		if (!tpm_chip_start(chip)) {
@@ -668,6 +674,9 @@ EXPORT_SYMBOL_GPL(tpm_chip_register);
  */
 void tpm_chip_unregister(struct tpm_chip *chip)
 {
+	if (tpm_locality_on_suspend)
+		chip->flags |= TPM_CHIP_PRESERVE_LOCALITY;
+
 	tpm_del_legacy_sysfs(chip);
 	if (tpm_is_hwrng_enabled(chip))
 		hwrng_unregister(&chip->hwrng);
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 66b16d26eecc..8aeea2dee0a8 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -26,6 +26,7 @@
 #include <linux/suspend.h>
 #include <linux/freezer.h>
 #include <linux/tpm_eventlog.h>
+#include <linux/dmi.h>
 
 #include "tpm.h"
 
@@ -382,6 +383,34 @@ int tpm_auto_startup(struct tpm_chip *chip)
 	return rc;
 }
 
+/*
+ * Bug workaround - some boards expect the TPM to be on ready
+ * state before suspend/shutdown, otherwise suspend and shutdown might
+ * hang the system, so we need to adjust suspend code for handling this.
+ */
+bool tpm_locality_on_suspend;
+module_param_named(locality_on_suspend, tpm_locality_on_suspend, bool, 0644);
+MODULE_PARM_DESC(locality_on_suspend, "The firmware expects TPM to be at locality 0 before suspend/shutdown.");
+
+static int __init tpm_set_locality_on_suspend(const struct dmi_system_id *system_id)
+{
+	pr_info("Board %s: TPM locality preserved before suspend/shutdown.\n", system_id->ident);
+	tpm_locality_on_suspend = true;
+
+	return 0;
+}
+
+static const struct dmi_system_id tpm_board_quirks[] __initconst = {
+	{
+		.ident = "TUF GAMING B460M-PLUS",
+		.matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "ASUSTeK COMPUTER INC."),
+			DMI_MATCH(DMI_BOARD_NAME, "TUF GAMING B460M-PLUS"),
+		},
+		.callback = tpm_set_locality_on_suspend,
+	},
+};
+
 /*
  * We are about to suspend. Save the TPM state
  * so that it can be restored.
@@ -394,6 +423,9 @@ int tpm_pm_suspend(struct device *dev)
 	if (!chip)
 		return -ENODEV;
 
+	if (tpm_locality_on_suspend)
+		chip->flags |= TPM_CHIP_PRESERVE_LOCALITY;
+
 	if (chip->flags & TPM_CHIP_FLAG_ALWAYS_POWERED)
 		goto suspended;
 
@@ -431,7 +463,7 @@ int tpm_pm_resume(struct device *dev)
 	if (chip == NULL)
 		return -ENODEV;
 
-	chip->flags &= ~TPM_CHIP_FLAG_SUSPENDED;
+	chip->flags &= ~(TPM_CHIP_PRESERVE_LOCALITY | TPM_CHIP_FLAG_SUSPENDED);
 
 	/*
 	 * Guarantee that SUSPENDED is written last, so that hwrng does not
@@ -476,6 +508,8 @@ static int __init tpm_init(void)
 {
 	int rc;
 
+	dmi_check_system(tpm_board_quirks);
+
 	rc = class_register(&tpm_class);
 	if (rc) {
 		pr_err("couldn't create tpm class\n");
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 61445f1dc46d..f2657b611b81 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -236,6 +236,7 @@ extern dev_t tpm_devt;
 extern const struct file_operations tpm_fops;
 extern const struct file_operations tpmrm_fops;
 extern struct idr dev_nums_idr;
+extern bool tpm_locality_on_suspend;
 
 ssize_t tpm_transmit(struct tpm_chip *chip, u8 *buf, size_t bufsiz);
 int tpm_get_timeouts(struct tpm_chip *);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 4ee9d13749ad..7717f484ac25 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -284,6 +284,7 @@ enum tpm_chip_flags {
 	TPM_CHIP_FLAG_FIRMWARE_UPGRADE		= BIT(7),
 	TPM_CHIP_FLAG_SUSPENDED			= BIT(8),
 	TPM_CHIP_FLAG_HWRNG_DISABLED		= BIT(9),
+	TPM_CHIP_PRESERVE_LOCALITY		= BIT(10),
 };
 
 #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)
-- 
2.44.0