| b.liu | e958203 | 2025-04-17 19:18:16 +0800 | [diff] [blame] | 1 | What: /sys/bus/i2c/devices/.../bd9571mwv-regulator.*.auto/backup_mode |
| 2 | Date: Jul 2018 |
| 3 | KernelVersion: 4.19 |
| 4 | Contact: Geert Uytterhoeven <geert+renesas@glider.be> |
| 5 | Description: Read/write the current state of DDR Backup Mode, which controls |
| 6 | if DDR power rails will be kept powered during system suspend. |
| 7 | ("on"/"1" = enabled, "off"/"0" = disabled). |
| 8 | Two types of power switches (or control signals) can be used: |
| 9 | A. With a momentary power switch (or pulse signal), DDR |
| 10 | Backup Mode is enabled by default when available, as the |
| 11 | PMIC will be configured only during system suspend. |
| 12 | B. With a toggle power switch (or level signal), the |
| 13 | following steps must be followed exactly: |
| 14 | 1. Configure PMIC for backup mode, to change the role of |
| 15 | the accessory power switch from a power switch to a |
| 16 | wake-up switch, |
| 17 | 2. Switch accessory power switch off, to prepare for |
| 18 | system suspend, which is a manual step not controlled |
| 19 | by software, |
| 20 | 3. Suspend system, |
| 21 | 4. Switch accessory power switch on, to resume the |
| 22 | system. |
| 23 | DDR Backup Mode must be explicitly enabled by the user, |
| 24 | to invoke step 1. |
| 25 | See also Documentation/devicetree/bindings/mfd/bd9571mwv.txt. |
| 26 | Users: User space applications for embedded boards equipped with a |
| 27 | BD9571MWV PMIC. |