mirror of
https://github.com/smaeul/u-boot.git
synced 2025-11-03 21:48:15 +00:00
23 lines
942 B
Plaintext
23 lines
942 B
Plaintext
Lite5200B wakeup from low-power mode (CONFIG_LITE5200B_PM)
|
|
----------------------------------------------------------
|
|
|
|
Low-power mode as described in Lite5200B User's Manual, means that
|
|
with support of MC68HLC908QT1 microcontroller (refered to as QT),
|
|
everything but the SDRAM can be powered down. This brings
|
|
maximum power saving, while one can still restore previous state
|
|
quickly.
|
|
|
|
Quick overview where U-Boot comes into the picture:
|
|
- OS saves device states
|
|
- OS saves wakeup handler address to physical 0x0, puts SDRAM into
|
|
self-refresh and signals to QT, it should power down the board
|
|
- / board is sleeping here /
|
|
- someone presses SW4 (connected to QT)
|
|
- U-Boot checks PSC2_4 pin, if QT drives it down, then we woke up,
|
|
so get SDRAM out of self-refresh and transfer control to OS
|
|
wakeup handler
|
|
- OS restores device states
|
|
|
|
This was tested on Linux with USB and Ethernet in use. Adding
|
|
support for other devices is an OS issue.
|