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