| 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. |
