Am 19.01.2014 um 13:19 schrieb Igor Gnatenko [off-list ref]:

On Sun, 2014-01-19 at 11:57 +0100, Sergei Antonov wrote:

quoted

quoted

Am 17.01.2014 um 11:06 schrieb Stanislaw Gruszka [off-list ref]:

quoted

On Tue, Jan 14, 2014 at 07:28:39PM +0100, Sergei Antonov wrote:
Hello!
I use a USB Wi-Fi adapter identified as follows.

usb 2-4: new high-speed USB device number 5 using ehci-pci
usb 2-4: New USB device found, idVendor=148f, idProduct=5370
usb 2-4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 2-4: Product: 802.11 n WLAN
usb 2-4: Manufacturer: Ralink
usb 2-4: SerialNumber: 1.0
usb 2-4: reset high-speed USB device number 5 using ehci-pci
ieee80211 phy3: rt2x00_set_rt: Info - RT chipset 5390, rev 0502 detected
ieee80211 phy3: rt2x00_set_rf: Info - RF chipset 5370 detected

It worked well with older kernels and does not with newer kernels.
Specifically it fails to find any AP when scanning.
The first bad commit is:

commit 76773f301f2210dcc20c466aebda7118062673eb
Author: Gabor Juhos [off-list ref]
Date:   Sat Aug 17 14:09:30 2013 +0200

  rt2x00: rt2800lib: use a MCU command for frequency adjustment on USB devices

  According to the Ralink driver, there is an MCU
  command which can be used to send the frequency
  offset value directly to the USB device without
  going through the RFCSR writing sequence.

  Based on the DPO_RT5572_LinuxSTA_2.6.0.1_20120629
  driver.

  Reference:
    RTMPAdjustFrequencyOffset function in common/rt_rf.c

  Signed-off-by: Gabor Juhos [off-list ref]
  Signed-off-by: John W. Linville [off-list ref]

After I removed this special USB handling (see the patch) the adapter
works again.

Thanks for bisecting! Could you check if following patch fixes the
issue?

It does not fix the issue. The same broken behavior remains.

I couldn't understand one string in original RTMPAdjustFrequencyOffset. Could you try follow patch ?

Tried your patch with and without Stanislaw's patch. No success.