tpm: do not suspend/resume if power stays on

BugLink: https://bugs.launchpad.net/bugs/1777063

commit b5d0ebc9 upstream.

The suspend/resume behavior of the TPM can be controlled by setting
"powered-while-suspended" in the DTS. This is useful for the cases
when hardware does not power-off the TPM.
Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/char/tpm/tpm-chip.c

@@ -26,6 +26,7 @@
 #include <linux/spinlock.h>
 #include <linux/freezer.h>
 #include <linux/major.h>
+#include <linux/of.h>
 #include "tpm.h"
 #include "tpm_eventlog.h"
 
@@ -328,8 +329,20 @@ static void tpm1_chip_unregister(struct tpm_chip *chip)
  */
 int tpm_chip_register(struct tpm_chip *chip)
 {
+#ifdef CONFIG_OF
+	struct device_node *np;
+#endif
 	int rc;
 
+#ifdef CONFIG_OF
+	np = of_find_node_by_name(NULL, "vtpm");
+	if (np) {
+		if (of_property_read_bool(np, "powered-while-suspended"))
+			chip->flags |= TPM_CHIP_FLAG_ALWAYS_POWERED;
+	}
+	of_node_put(np);
+#endif
+
 	rc = tpm1_chip_register(chip);
 	if (rc)
 		return rc;

drivers/char/tpm/tpm-interface.c

@@ -948,6 +948,9 @@ int tpm_pm_suspend(struct device *dev)
 	if (chip == NULL)
 		return -ENODEV;
 
+	if (chip->flags & TPM_CHIP_FLAG_ALWAYS_POWERED)
+		return 0;
+
 	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
 		tpm2_shutdown(chip, TPM2_SU_STATE);
 		return 0;

drivers/char/tpm/tpm.h

@@ -164,6 +164,7 @@ struct tpm_vendor_specific {
 enum tpm_chip_flags {
 	TPM_CHIP_FLAG_REGISTERED	= BIT(0),
 	TPM_CHIP_FLAG_TPM2		= BIT(1),
+	TPM_CHIP_FLAG_ALWAYS_POWERED	= BIT(5),
 };
 
 struct tpm_chip {