| 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/rohm,bd9571mwv.yaml. | |
| Users: User space applications for embedded boards equipped with a | |
| BD9571MWV PMIC. |