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+What: /sys/bus/i2c/devices/.../bd9571mwv-regulator.*.auto/backup_mode
+Date: Jul 2018
+KernelVersion: 4.19
+Contact: Geert Uytterhoeven <geert+renesas@glider.be>
+Description: Read/write the current state of DDR Backup Mode, which controls
+ if DDR power rails will be kept powered during system suspend.
+ ("on"/"1" = enabled, "off"/"0" = disabled).
+ Two types of power switches (or control signals) can be used:
+
+ A. With a momentary power switch (or pulse signal), DDR
+ Backup Mode is enabled by default when available, as the
+ PMIC will be configured only during system suspend.
+ B. With a toggle power switch (or level signal), the
+ following steps must be followed exactly:
+
+ 1. Configure PMIC for backup mode, to change the role of
+ the accessory power switch from a power switch to a
+ wake-up switch,
+ 2. Switch accessory power switch off, to prepare for
+ system suspend, which is a manual step not controlled
+ by software,
+ 3. Suspend system,
+ 4. Switch accessory power switch on, to resume the
+ system.
+
+ DDR Backup Mode must be explicitly enabled by the user,
+ to invoke step 1.
+
+ See also Documentation/devicetree/bindings/mfd/bd9571mwv.txt.
+Users: User space applications for embedded boards equipped with a
+ BD9571MWV PMIC.