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| author | fishsoupisgood <github@madingley.org> | 2019-04-29 01:17:54 +0100 |
|---|---|---|
| committer | fishsoupisgood <github@madingley.org> | 2019-05-27 03:43:43 +0100 |
| commit | 3f2546b2ef55b661fd8dd69682b38992225e86f6 (patch) | |
| tree | 65ca85f13617aee1dce474596800950f266a456c /roms/u-boot/board/icecube/README.Lite5200B_low_power | |
| download | qemu-master.tar.gz qemu-master.tar.bz2 qemu-master.zip | |
Diffstat (limited to 'roms/u-boot/board/icecube/README.Lite5200B_low_power')
| -rw-r--r-- | roms/u-boot/board/icecube/README.Lite5200B_low_power | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/roms/u-boot/board/icecube/README.Lite5200B_low_power b/roms/u-boot/board/icecube/README.Lite5200B_low_power new file mode 100644 index 00000000..5b04fbba --- /dev/null +++ b/roms/u-boot/board/icecube/README.Lite5200B_low_power @@ -0,0 +1,22 @@ +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. |