unstable wifi operation with BCM4331 and mainline kernel 3.19 using bcmwl

Hello,

I installed bcmwl-kernel-source_6.30.223.248+bdcom-0ubuntu2_amd64.deb on laptop running mainline kernel
 3.19.0-031900-generic
on Ubuntu 14.04.2 LTS

I am experiencing an unstable wifi connection particularly but not limited to 2.4 GHz band access points

problems include:

-high rate of dropped packets and long ping times. The connection seems to be stable for several minutes then ping would report very high round-trip times and packets are dropped:
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=151 ttl=53 time=17.2 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=152 ttl=53 time=11.4 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=153 ttl=53 time=23.9 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=154 ttl=53 time=11.9 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=155 ttl=53 time=11.1 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=158 ttl=53 time=622 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=159 ttl=53 time=25.3 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=160 ttl=53 time=162 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=161 ttl=53 time=490 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=162 ttl=53 time=557 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=163 ttl=53 time=58.7 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=164 ttl=53 time=608 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=165 ttl=53 time=687 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=166 ttl=53 time=724 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=167 ttl=53 time=576 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=169 ttl=53 time=19.6 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=170 ttl=53 time=12.7 ms
64 bytes from fra07s28-in-f20.1e100.net (173.194.112.52): icmp_seq=171 ttl=53 time=12.2 ms

sometimes the connection is lost alltogether (no hosts pingable) even though the network manager reports that the connection is up. Disconnecting and re-connecting or disabling-enabling wifi temporarily helps

-authentication loops where the network manager tries to connect to an access point, disconnects again etc in a loop that can last several minutes before the connection is established. Syslog section from when I disabled wifi and re-enabled on pastebin:
http://pastebin.ubuntu.com/10549778/

-frequent error reports in the syslog:
Mar 6 11:21:57 tachyon3 kernel: [ 3981.049295] ERROR @wl_inform_single_bss : cfg80211_inform_bss_frame error
Mar 6 11:22:18 tachyon3 kernel: [ 4002.097357] ERROR @wl_dev_intvar_get : error (-1)
Mar 6 11:22:18 tachyon3 kernel: [ 4002.097362] ERROR @wl_cfg80211_get_tx_power : error (-1)
Mar 6 11:22:19 tachyon3 kernel: [ 4003.038068] ERROR @wl_dev_intvar_get : error (-1)
Mar 6 11:22:19 tachyon3 kernel: [ 4003.038073] ERROR @wl_cfg80211_get_tx_power : error (-1)
Mar 6 11:23:00 tachyon3 kernel: [ 4044.062783] ERROR @wl_inform_single_bss : cfg80211_inform_bss_frame error
Mar 6 11:24:23 tachyon3 kernel: [ 4127.269626] ERROR @wl_inform_single_bss : cfg80211_inform_bss_frame error
Mar 6 11:26:06 tachyon3 kernel: [ 4230.249434] ERROR @wl_inform_single_bss : cfg80211_inform_bss_frame error

-very occasional system hangs when connecting or disconnecting to wifi, enabling disabling wifi, particularly short time after suspend

The hardware is:
04:00.0 Network controller [0280]: Broadcom Corporation BCM4331 802.11a/b/g/n [14e4:4331] (rev 02)
 Subsystem: Apple Inc. AirPort Extreme [106b:00ef]
 Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
 Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
 Latency: 0, Cache Line Size: 256 bytes
 Interrupt: pin A routed to IRQ 17
 Region 0: Memory at c1900000 (64-bit, non-prefetchable) [size=16K]
 Capabilities: [40] Power Management version 3
  Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
  Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=2 PME-

So there is a possible problem with the bcmwl driver... Could anyone take a look?

Thanks,
Wojtek