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.bin
Here is the link to the corresponding SL bug: https://bugs.sabayon.org/show_bug.cgi?id=2258