Bug 42826

I have had a Link Quality level problems with the r8712u staging driver on all 3.2.x (incuding rc's), and all 3.3.0-rc's, and Larry finger requested that I file a bug report, so here it is. 

This r8712u usb wireless problem has plagued me for weeks on countless 3.2.x and 3.3.0-rc kernels, on several Gentoo systems, and with Arch, Mageia Cauldron, and a few other distros.  It is consistent with Wicd, NetworkManager, or manually configured.

I'm using this hardware: Bus 001 Device 002: ID 0bda:8172 Realtek Semiconductor Corp. RTL8191SU 802.11n WLAN Adapter (Rosewill RNX-N180UBE b/g/n 300mps wireless adapter)   

The only work around I've found so far that works is this:
If I simply replace any linux-3.2.x/drivers/staging/rtl8712/ directory in the kernel source
with ANY 3.1 staging/rtl8712 version, and then recompile any 3.2.x kernel, all is
instantly well on reboot, with the normal rock solid 98% link/signal 3.1 levels of wifi performance

Here are some more relevant comments from a discussion at:      https://bugs.archlinux.org/task/27996  

I can confirm on Gentoo with a vanilla 3.3.0-rc2, not setting CONFIG_R8712_AP=y works, at least partially. Unfortunately, the link/signal level is never higher than 44%, but at least it now functions.

With 3.3.0-rc2 and 3.2.x kernels using the linux-3.1.9/drivers/staging/rtl8712/ directory (replacing the 3.2/3.3 versions), levels are immediately on reboot my normal 98-100%.

So it appears that while just not setting CONFIG_R8712_AP=y does enable a connection and scanning, there is still something different in the 3.2/3.3 versions that limits connection quality and speed.

EDIT: FWIW, a minute or so after I posted the above, wicd reported the connection fluctuating briefly up to 57% for a few seconds at a time, and a brief green bar instead of yellow.
With 3.1.x kernels, and even with CONFIG_R8712_AP=y set, this never happens- the connection is ALWAYS a constant rock solid 98-100%, with solid green bars.

Then, a few days later after some more struggling around, where Larry had fixed some other issues:

The new r8712u driver works in 3.2.x's, and 3.3-rc's, but the link quality is still never better than 44%, and usually around 26-42%, with disconnects common. On the latest Arch Linux (testing 3.2.2 kernel, with NM freshly configured), r8712u loads, but neither NM or for that matter wicd is functional. On arch, I had to go back to a TP-Link WN722N USB adapter (ath9k chip), where Arch auto-detects and brings up wireless, but at only the 40% signal quality. (This might be just the TP-Link adapter, and not kernel related)

Went back to Gentoo, and compiled the freshest new 3.3.0-rc4, and 3.2.6 kernels just downloaded from kernel.org. Same low signal quality as before. I was hoping the new patches from Larry had done the trick, but apparently not, at least on my systems with the Rosewill usb r8712u adapter.

Once again, I copied over the 3.1.9 /staging/rtl8712 directory to the new kernels, and rebuilt the r8712u module in both 3.2.6 and 3.3.0-rc4.
Again, same great result. NM wireless immediately comes up normally showing 9 AP's, with a rock solid 98-99% link quality to my wpa-psk G router, no disconnects.

It seems apparent something regarding r8712u link/signal quality has gone amiss as of 3.2-rc kernels, and so far remains unresolved notwithstanding the other problems that were addressed.