I had exactly the same problem on my u210 running SL6 and managed to fix the problem. Not sure if my approach still works on SL7.
The problem was the SL looked for
/lib/firmware/rt3090.bin and that file was not present. But firmware for rt3090 is the same as for rt2860 (and similar chips). And
rt2860.bin is already present in /lib/firmware.
So you have 2 solutions:
1) make symlink named
rt3090.bin (in /lib/firmware) and point it to
rt2860.bin.
2) make a copy of
rt2860.bin and rename the copy into
rt3090.binHere is the link to the corresponding SL bug:
https://bugs.sabayon.org/show_bug.cgi?id=2258