problems with madwifi and Atheros AR5418

[mpg <mpg@elzevir.fr>]

Hi all,

My new laptop (asus F80L-4P007C) comes with an Atheros AR5418 wifi chipset,
which apparently doesn't work well with madwifi from current Lenny. This
chipset is reported to work with madwifi at:

        http://madwifi.org/wiki/Compatibility/Atheros#AtherosAR5418

I have packet loss varying form 0% to 85%, even pinging my local gateway
(which is also the wifi AP). The only other abnormal things I noticed are
the message 

        wifi0: unknow hardware address type 801

issued (two times) when I ran 'dhclient ath0' (after configuring the card
with iwconfig and bringing it up with ifconfig).

Now, after some time using it, I have:

mpg@roth:~% /sbin/iwconfig ath0
ath0      IEEE 802.11g  ESSID:"freeboite"  Nickname:""
          Mode:Managed  Frequency:2.412 GHz  Access Point: 96:8C:04:33:F8:1C
          Bit Rate:48 Mb/s   Tx-Power:14 dBm   Sensitivity=1/1
          Retry:off   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=65/70  Signal level=-31 dBm  Noise level=-96 dBm
          Rx invalid nwid:47937  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

I notice that 'Rx invalid nwid' is non-zero, but don't know how to use this
information.

What can I do in order to debug or work around this problem?

For now the options I can see are:
1. Use a more recent madwifi snapshot.
2. Try a 2.6.27 kernel with the new ath9k driver which is supposed to handle
my chipset.
3. Use the win32 driver via ndiswrapper. I don't like this option at all, it
also forces me to re-install everything in 32bits...

Any sensible advice greatly welcome! I include some info which my be useful,
feel free to ask more if I forgot something important.

TIA,
Manuel.

mpg@roth:~% lspci | grep -i wireless 
02:00.0 Network controller: Atheros Communications Inc. AR5418 802.11abgn
Wireless PCI Express Adapter (rev 01)
mpg@roth:~% lspci -v -s 02:00.0
02:00.0 Network controller: Atheros Communications Inc. AR5418 802.11abgn
Wireless PCI Express Adapter (rev 01)
        Subsystem: Atheros Communications Inc. Device 3072
        Flags: bus master, fast devsel, latency 0, IRQ 17
        Memory at fdef0000 (64-bit, non-prefetchable) [size=64K]
        Capabilities: <access denied>
        Kernel driver in use: ath_pci
        Kernel modules: ath_pci, ath5k
roth:~# lsmod G 'ath|wlan'
wlan_wep                9984  1 
wlan_scan_sta          17280  1 
ath_rate_sample        17024  1 
ath_pci               241600  0 
wlan                  223904  5
wlan_wep,wlan_scan_sta,ath_rate_sample,ath_pci
ath_hal               334480  3 ath_rate_sample,ath_pci
mpg@roth:~% uname -a               
Linux roth 2.6.26-1-amd64 #1 SMP Wed Aug 20 12:09:32 UTC 2008 x86_64
GNU/Linux