diff --git a/Documentation/power/states.txt b/Documentation/power/states.txt
index bc4548245a24..205e45ad7c65 100644
--- a/Documentation/power/states.txt
+++ b/Documentation/power/states.txt
@@ -35,7 +35,9 @@ only one way to cause the system to go into the Suspend-To-RAM state (write
 The default suspend mode (ie. the one to be used without writing anything into
 /sys/power/mem_sleep) is either "deep" (if Suspend-To-RAM is supported) or
 "s2idle", but it can be overridden by the value of the "mem_sleep_default"
-parameter in the kernel command line.
+parameter in the kernel command line.  On some ACPI-based systems, depending on
+the information in the FADT, the default may be "s2idle" even if Suspend-To-RAM
+is supported.
 
 The properties of all of the sleep states are described below.
 
diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
index be17664736b2..b363283dfcd9 100644
--- a/drivers/acpi/sleep.c
+++ b/drivers/acpi/sleep.c
@@ -714,6 +714,12 @@ static int lps0_device_attach(struct acpi_device *adev,
 		if ((bitmask & ACPI_S2IDLE_FUNC_MASK) == ACPI_S2IDLE_FUNC_MASK) {
 			lps0_dsm_func_mask = bitmask;
 			lps0_device_handle = adev->handle;
+			/*
+			 * Use suspend-to-idle by default if the default
+			 * suspend mode was not set from the command line.
+			 */
+			if (mem_sleep_default > PM_SUSPEND_MEM)
+				mem_sleep_current = PM_SUSPEND_FREEZE;
 		}
 
 		acpi_handle_debug(adev->handle, "_DSM function mask: 0x%x\n",
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 97e394feabdb..8c3b0b1e6786 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -196,6 +196,9 @@ struct platform_freeze_ops {
 };
 
 #ifdef CONFIG_SUSPEND
+extern suspend_state_t mem_sleep_current;
+extern suspend_state_t mem_sleep_default;
+
 /**
  * suspend_set_ops - set platform dependent suspend operations
  * @ops: The new suspend operations to set.
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 268c1b0afc28..1d2d761e3c25 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -192,7 +192,6 @@ extern void swsusp_show_speed(ktime_t, ktime_t, unsigned int, char *);
 extern const char * const pm_labels[];
 extern const char *pm_states[];
 extern const char *mem_sleep_states[];
-extern suspend_state_t mem_sleep_current;
 
 extern int suspend_devices_and_enter(suspend_state_t state);
 #else /* !CONFIG_SUSPEND */
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 4bce46ddc2cd..0639d3a79852 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -48,7 +48,7 @@ static const char * const mem_sleep_labels[] = {
 const char *mem_sleep_states[PM_SUSPEND_MAX];
 
 suspend_state_t mem_sleep_current = PM_SUSPEND_FREEZE;
-static suspend_state_t mem_sleep_default = PM_SUSPEND_MEM;
+suspend_state_t mem_sleep_default = PM_SUSPEND_MAX;
 suspend_state_t pm_suspend_target_state;
 EXPORT_SYMBOL_GPL(pm_suspend_target_state);
 
@@ -216,7 +216,7 @@ void suspend_set_ops(const struct platform_suspend_ops *ops)
 	}
 	if (valid_state(PM_SUSPEND_MEM)) {
 		mem_sleep_states[PM_SUSPEND_MEM] = mem_sleep_labels[PM_SUSPEND_MEM];
-		if (mem_sleep_default == PM_SUSPEND_MEM)
+		if (mem_sleep_default >= PM_SUSPEND_MEM)
 			mem_sleep_current = PM_SUSPEND_MEM;
 	}