Regression in ath driver with AR9280 at revision 203159

Good day,

I own an Acer Aspire 5535 which is equipped with an AR9280 wireless
chipset. From revision 203159 it simply stopped working: ifconfig
shows "no carrier" and ifconfig wlan0 scan has no output. Up to
r203158 everything was ok.

pciconf -lcvb:
ath0_at_pci0:6:0:0:	class=0x028000 card=0x03031a32 chip=0x002a168c
rev=0x01 hdr=0x00
    vendor     = 'Atheros Communications Inc.'
    device     = 'Atheros AR5B91 Wireless Network Adapter (0001)'
    class      = network
    bar   [10] = type Memory, range 64, base 0xf0400000, size 65536, enabled
    cap 01[40] = powerspec 2  supports D0 D1 D3  current D0
    cap 05[50] = MSI supports 1 message
    cap 10[60] = PCI-Express 1 legacy endpoint max data 128(128) link x1(x1)
    cap 11[90] = MSI-X supports 1 message in map 0x10

verbose dmesg:
ath0: <Atheros 9280> mem 0xf0400000-0xf040ffff irq 18 at device 0.0 on pci6
ath0: [MPSAFE]
ath0: [ITHREAD]
ath0: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps
ath0: 11g rates: 1Mbps 2Mbps 5.5Mbps 11Mbps 6Mbps 9Mbps 12Mbps 18Mbps
24Mbps 36Mbps 48Mbps 54Mbps
ath0: 11ng MCS: 15Mbps 30Mbps 45Mbps 60Mbps 90Mbps 120Mbps 135Mbps
150Mbps 30Mbps 60Mbps 90Mbps 120Mbps 180Mbps 240Mbps 270Mbps 300Mbps
ath0: AR9280 mac 128.2 RF5133 phy 13.0
ath0: Use hw queue 1 for WME_AC_BE traffic
ath0: Use hw queue 0 for WME_AC_BK traffic
ath0: Use hw queue 2 for WME_AC_VI traffic
ath0: Use hw queue 3 for WME_AC_VO traffic
ath0: Use hw queue 8 for CAB traffic
ath0: Use hw queue 9 for beacons

Is there anything I could do?

Thanks
Fred