Am 23.12.2014 um 16:31 schrieb Jeremy Audet:

Hi Oleksij,

Sure thing. I cloned your ath9k-htc-firmware-blob repository and
copied the htc_9271.fw file to /usr/lib/firmware/. I then plugged in
the TL-WN722N USB adapter, brought up the wireless device with `sudo
ip link set dev wlp0s18f2u4 up; echo $?` (return code 0), and sat back
and waited. I did not interact with the machine beyond keeping open an
SSH session (via a wired interface) and watching the log file. About
five minutes later, a similar error occurred as described in my
previous email.

I've collected some logging output with the command `journalctl -k
--since=today`. You may find this log a bit more useful than the dmesg
log linked to in my previous email. You can find the log here:
http://www.ichimonji10.name/downloads/tl-wn722n-journalctl.txt

-Jeremy "Ichimonji10" Audet

So, at some point usb layer dropped connection, and reconnected in
full-speed mode, which is slow:
=================================================================
Dec 23 10:07:49 pine kernel: usb 5-4: USB disconnect, device number 9
Dec 23 10:07:49 pine kernel: ath: phy6: Failed to wakeup in 500us
Dec 23 10:07:50 pine kernel: ath: phy6: RX failed to go idle in 10 ms
RXSM=0xb063df84
Dec 23 10:07:50 pine kernel: ath: phy6: Failed to wakeup in 500us
Dec 23 10:07:50 pine kernel: usb 5-4: ath9k_htc: USB layer deinitialized
Dec 23 10:07:50 pine kernel: usb 5-4: new high-speed USB device number
10 using ehci-pci
Dec 23 10:07:51 pine kernel: usb 1-4: new full-speed USB device number 5
using ohci-pci
Dec 23 10:07:51 pine kernel: usb 1-4: not running at top speed; connect
to a high speed hub
Dec 23 10:07:51 pine kernel: usb 1-4: ath9k_htc: Firmware htc_9271.fw
requested
Dec 23 10:07:51 pine kernel: usb 1-4: ath9k_htc: Transferred FW:
htc_9271.fw, size: 51008
==================================================================

After reconnecting to fulls-speed, ath9k-htc was unusable. I would
suggest to test other cable or other usb controller.
With other words, I have no idea about the reason for initial
disconnection. It can be bad usb connection, noise or not enough power.

-- 
Regards,
Oleksij