byzantium,
I thought you had a SL-6000. (don't ask me why). Now, your question makes me think that, perhaps, you have another one.
As I have said before, with the 6000 and using Debian over Xqt, all the standard capabilities of the original ROM are maintained. So, to suspend and come back it should be done exactly the same as if you were not using Debian: tap the power button.
From inside Debian, it could be possible to suspend from the command line, but totally impossible to resume :-) Anyway, to try to suspend from the command line you should have available the original directory " /dev ". This is possible if you mount not only " /proc " but also " /dev ". You can do it with: " mount -o bind ", but, probably, you will have some new problems with ttys. Don't forget that you cal always open an original Qtopia console and do there anything allowed in the original ROM.
smuelas