[PATCH v3 01/10] PM: suspend: Introduce `pm_suspend_preferred_s2idle`

[Mario Limonciello]

Many drivers in the kernel will check the FADT to determine if low
power idle is supported and use this information to set up a policy
decision in the driver.  To abstract this information from drivers
introduce a new helper symbol that can indicate this information.

Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
 include/linux/suspend.h |  1 +
 kernel/power/suspend.c  | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 70f2921e2e70..9d911e026720 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -305,6 +305,7 @@ static inline bool idle_should_enter_s2idle(void)
 	return unlikely(s2idle_state == S2IDLE_STATE_ENTER);
 }
 
+extern bool pm_suspend_preferred_s2idle(void);
 extern bool pm_suspend_default_s2idle(void);
 extern void __init pm_states_init(void);
 extern void s2idle_set_ops(const struct platform_s2idle_ops *ops);
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 827075944d28..0030e7dfe6cf 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -9,6 +9,7 @@
 
 #define pr_fmt(fmt) "PM: " fmt
 
+#include <linux/acpi.h>
 #include <linux/string.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
@@ -61,6 +62,22 @@ static DECLARE_SWAIT_QUEUE_HEAD(s2idle_wait_head);
 enum s2idle_states __read_mostly s2idle_state;
 static DEFINE_RAW_SPINLOCK(s2idle_lock);
 
+/**
+ * pm_suspend_preferred_s2idle - Check if suspend-to-idle is the preferred suspend method.
+ *
+ * Return 'true' if suspend-to-idle is preferred by the system designer for the default
+ * suspend method.
+ */
+bool pm_suspend_preferred_s2idle(void)
+{
+#ifdef CONFIG_ACPI
+	return acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0;
+#else
+	return false;
+#endif
+}
+EXPORT_SYMBOL_GPL(pm_suspend_preferred_s2idle);
+
 /**
  * pm_suspend_default_s2idle - Check if suspend-to-idle is the default suspend.
  *
-- 
2.34.1