[PATCH v2 1/2] PM: enable support for imminent power loss

[shiva.linuxworks at gmail.com]

From: Shivamurthy Shastri <sshivamurthy at micron.com>

If the shutdown is pwerformed when the platform is running on the
limited backup power supply, some of the devices might not have enough
power to perform a clean shutdown.

It is necessary to inform the driver about the limited backup power
supply, to allow the driver to decide to perform the minimal required
operation for a fast and clean shutdown.

Signed-off-by: Keith Busch <kbush at kernel.org>
Signed-off-by: Shivamurthy Shastri <sshivamurthy at micron.com>
---
 include/linux/suspend.h | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 8af13ba60c7e..1898792c10d3 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -210,9 +210,10 @@ extern int suspend_valid_only_mem(suspend_state_t state);
 
 extern unsigned int pm_suspend_global_flags;
 
-#define PM_SUSPEND_FLAG_FW_SUSPEND	BIT(0)
-#define PM_SUSPEND_FLAG_FW_RESUME	BIT(1)
-#define PM_SUSPEND_FLAG_NO_PLATFORM	BIT(2)
+#define PM_SUSPEND_FLAG_FW_SUSPEND		BIT(0)
+#define PM_SUSPEND_FLAG_FW_RESUME		BIT(1)
+#define PM_SUSPEND_FLAG_NO_PLATFORM		BIT(2)
+#define PM_SUSPEND_FLAG_POWER_LOSS_IMMINENT	BIT(3)
 
 static inline void pm_suspend_clear_flags(void)
 {
@@ -234,6 +235,11 @@ static inline void pm_set_suspend_no_platform(void)
 	pm_suspend_global_flags |= PM_SUSPEND_FLAG_NO_PLATFORM;
 }
 
+static inline void pm_set_power_loss_imminent(void)
+{
+	pm_suspend_global_flags |= PM_SUSPEND_FLAG_POWER_LOSS_IMMINENT;
+}
+
 /**
  * pm_suspend_via_firmware - Check if platform firmware will suspend the system.
  *
@@ -291,6 +297,22 @@ static inline bool pm_suspend_no_platform(void)
 	return !!(pm_suspend_global_flags & PM_SUSPEND_FLAG_NO_PLATFORM);
 }
 
+/**
+ * pm_power_loss_imminent - Check if platform is running on limited backup power
+ * source
+ *
+ * To be called during system-wide power management transitions to sleep states.
+ *
+ * Return 'true' if power loss may be imminent due to platform running on
+ * limited backup supply. If set during a shutdown, drivers should use any
+ * available shortcuts to prepare their device for abrupt power loss.
+ */
+static inline bool pm_power_loss_imminent(void)
+{
+	return !!(pm_suspend_global_flags &
+		  PM_SUSPEND_FLAG_POWER_LOSS_IMMINENT);
+}
+
 /* Suspend-to-idle state machnine. */
 enum s2idle_states {
 	S2IDLE_STATE_NONE,      /* Not suspended/suspending. */
-- 
2.25.1