rt2x00: disable TKIP on USB

commit 8edcb0ba upstream.

On USB we can not get atomically TKIP key. We have to disable support
for TKIP acceleration on USB hardware to avoid bug as showed bellow.

[  860.827243] BUG: scheduling while atomic: hostapd/3397/0x00000002
<snip>
[  860.827280] Call Trace:
[  860.827282]  [<ffffffff81682ea6>] dump_stack+0x4d/0x66
[  860.827284]  [<ffffffff8167eb9b>] __schedule_bug+0x47/0x55
[  860.827285]  [<ffffffff81685bb3>] __schedule+0x733/0x7b0
[  860.827287]  [<ffffffff81685c59>] schedule+0x29/0x70
[  860.827289]  [<ffffffff81684f8a>] schedule_timeout+0x15a/0x2b0
[  860.827291]  [<ffffffff8105ac50>] ? ftrace_raw_event_tick_stop+0xc0/0xc0
[  860.827294]  [<ffffffff810c13c2>] ? __module_text_address+0x12/0x70
[  860.827296]  [<ffffffff81686823>] wait_for_completion_timeout+0xb3/0x140
[  860.827298]  [<ffffffff81080fc0>] ? wake_up_state+0x20/0x20
[  860.827301]  [<ffffffff814d5b3d>] usb_start_wait_urb+0x7d/0x150
[  860.827303]  [<ffffffff814d5cd5>] usb_control_msg+0xc5/0x110
[  860.827305]  [<ffffffffa02fb0c6>] rt2x00usb_vendor_request+0xc6/0x160  [rt2x00usb]
[  860.827307]  [<ffffffffa02fb215>] rt2x00usb_vendor_req_buff_lock+0x75/0x150 [rt2x00usb]
[  860.827309]  [<ffffffffa02fb393>] rt2x00usb_vendor_request_buff+0xa3/0xe0 [rt2x00usb]
[  860.827311]  [<ffffffffa023d1a3>] rt2x00usb_register_multiread+0x33/0x40 [rt2800usb]
[  860.827314]  [<ffffffffa05805f9>] rt2800_get_tkip_seq+0x39/0x50  [rt2800lib]
[  860.827321]  [<ffffffffa0480f88>] ieee80211_get_key+0x218/0x2a0  [mac80211]
[  860.827322]  [<ffffffff815cc68c>] ? __nlmsg_put+0x6c/0x80
[  860.827329]  [<ffffffffa051b02e>] nl80211_get_key+0x22e/0x360 [cfg80211]
Reported-and-tested-by: Peter Wu <lekensteyn@gmail.com>
Reported-and-tested-by: Pontus Fuchs <pontus.fuchs@gmail.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/wireless/rt2x00/rt2x00mac.c

@@ -517,6 +517,8 @@ int rt2x00mac_set_key(struct ieee80211_hw *hw, enum set_key_cmd cmd,
 	crypto.cipher = rt2x00crypto_key_to_cipher(key);
 	if (crypto.cipher == CIPHER_NONE)
 		return -EOPNOTSUPP;
+	if (crypto.cipher == CIPHER_TKIP && rt2x00_is_usb(rt2x00dev))
+		return -EOPNOTSUPP;
 
 	crypto.cmd = cmd;