What: /sys/bus/i2c/devices/.../bd9571mwv-regulator.*.auto/backup_mode Date: Jul 2018 KernelVersion: 4.19 Contact: Geert Uytterhoeven 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/rohm,bd9571mwv.yaml. Users: User space applications for embedded boards equipped with a BD9571MWV PMIC.