README.Lite5200B_low_power 942 B

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  1. Lite5200B wakeup from low-power mode (CONFIG_LITE5200B_PM)
  2. ----------------------------------------------------------
  3. Low-power mode as described in Lite5200B User's Manual, means that
  4. with support of MC68HLC908QT1 microcontroller (refered to as QT),
  5. everything but the SDRAM can be powered down. This brings
  6. maximum power saving, while one can still restore previous state
  7. quickly.
  8. Quick overview where U-Boot comes into the picture:
  9. - OS saves device states
  10. - OS saves wakeup handler address to physical 0x0, puts SDRAM into
  11. self-refresh and signals to QT, it should power down the board
  12. - / board is sleeping here /
  13. - someone presses SW4 (connected to QT)
  14. - U-Boot checks PSC2_4 pin, if QT drives it down, then we woke up,
  15. so get SDRAM out of self-refresh and transfer control to OS
  16. wakeup handler
  17. - OS restores device states
  18. This was tested on Linux with USB and Ethernet in use. Adding
  19. support for other devices is an OS issue.