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Subject[PATCH v2 1/2] PM: enable support for imminent power loss
Date
From: Shivamurthy Shastri <sshivamurthy@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@kernel.org>
Signed-off-by: Shivamurthy Shastri <sshivamurthy@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
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