1cf18fd01SGeert UytterhoevenWhat: /sys/bus/i2c/devices/.../bd9571mwv-regulator.*.auto/backup_mode 2cf18fd01SGeert UytterhoevenDate: Jul 2018 3cf18fd01SGeert UytterhoevenKernelVersion: 4.19 4cf18fd01SGeert UytterhoevenContact: Geert Uytterhoeven <geert+renesas@glider.be> 5cf18fd01SGeert UytterhoevenDescription: Read/write the current state of DDR Backup Mode, which controls 6cf18fd01SGeert Uytterhoeven if DDR power rails will be kept powered during system suspend. 7cf18fd01SGeert Uytterhoeven ("on"/"1" = enabled, "off"/"0" = disabled). 8cf18fd01SGeert Uytterhoeven Two types of power switches (or control signals) can be used: 934433332SMauro Carvalho Chehab 10cf18fd01SGeert Uytterhoeven A. With a momentary power switch (or pulse signal), DDR 11cf18fd01SGeert Uytterhoeven Backup Mode is enabled by default when available, as the 12cf18fd01SGeert Uytterhoeven PMIC will be configured only during system suspend. 13cf18fd01SGeert Uytterhoeven B. With a toggle power switch (or level signal), the 14cf18fd01SGeert Uytterhoeven following steps must be followed exactly: 1534433332SMauro Carvalho Chehab 16cf18fd01SGeert Uytterhoeven 1. Configure PMIC for backup mode, to change the role of 17cf18fd01SGeert Uytterhoeven the accessory power switch from a power switch to a 18cf18fd01SGeert Uytterhoeven wake-up switch, 19cf18fd01SGeert Uytterhoeven 2. Switch accessory power switch off, to prepare for 20cf18fd01SGeert Uytterhoeven system suspend, which is a manual step not controlled 21cf18fd01SGeert Uytterhoeven by software, 22cf18fd01SGeert Uytterhoeven 3. Suspend system, 23cf18fd01SGeert Uytterhoeven 4. Switch accessory power switch on, to resume the 24cf18fd01SGeert Uytterhoeven system. 2534433332SMauro Carvalho Chehab 26cf18fd01SGeert Uytterhoeven DDR Backup Mode must be explicitly enabled by the user, 27cf18fd01SGeert Uytterhoeven to invoke step 1. 2834433332SMauro Carvalho Chehab 29cf18fd01SGeert Uytterhoeven See also Documentation/devicetree/bindings/mfd/bd9571mwv.txt. 30cf18fd01SGeert UytterhoevenUsers: User space applications for embedded boards equipped with a 31cf18fd01SGeert Uytterhoeven BD9571MWV PMIC. 32