tpm: do not suspend/resume if power stays on

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>

drivers/char/tpm/tpm-interface.c

@@ -1119,6 +1119,9 @@ 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

@@ -174,6 +174,7 @@ enum tpm_chip_flags {
 	TPM_CHIP_FLAG_IRQ		= BIT(2),
 	TPM_CHIP_FLAG_VIRTUAL		= BIT(3),
 	TPM_CHIP_FLAG_HAVE_TIMEOUTS	= BIT(4),
+	TPM_CHIP_FLAG_ALWAYS_POWERED	= BIT(5),
 };
 
 struct tpm_bios_log {

drivers/char/tpm/tpm_of.c

@@ -36,6 +36,9 @@ int tpm_read_log_of(struct tpm_chip *chip)
 	else
 		return -ENODEV;
 
+	if (of_property_read_bool(np, "powered-while-suspended"))
+		chip->flags |= TPM_CHIP_FLAG_ALWAYS_POWERED;
+
 	sizep = of_get_property(np, "linux,sml-size", NULL);
 	basep = of_get_property(np, "linux,sml-base", NULL);
 	if (sizep == NULL && basep == NULL)