ath5k: monitor mode needs channel change

ath5k: monitor mode needs channel change

[Joerg Albert]

I currently need an extra trigger by changing the channel after
"ifconfig up" to see any output in monitor mode from ath5k, e.g.

ifconfig wlan0 down
iwconfig wlan0 mode monitor channel 1
ifconfig wlan0 up
# no output by tcpdump -n -i wlan0  in another xterm
iwconfig wlan0 channel 2
# tcpdump output starts

The second "iwconfig" call must specify a channel different to the
first one.

The above sequence without the second "iwconfig" works fine with a
RTL8187 device.

I'm running
compat-wireless-2.6: master-2009-07-26-11-g83c091c
wireless-testing: v2.6.31-rc4-29204-g6b3a8c9
on top of a 2.6.30 kernel.

The WLAN NIC is a:

02:00.0 Ethernet controller: Atheros Communications Inc. AR242x
802.11abg Wireless PCI Express Adapter (rev 01),
PCI id: 168c:001c (rev 01)

ath5k identifies it as:

ath5k phy0: Atheros AR2425 chip found (MAC: 0xe2, PHY: 0x70)

It's not a big issue, but a bit annoying sometimes.

Re: ath5k: monitor mode needs channel change

[Bob Copeland]

On Thu, Jul 30, 2009 at 5:31 PM, Joerg Albert<jal2@gmx.de> wrote:
> I currently need an extra trigger by changing the channel after
> "ifconfig up" to see any output in monitor mode from ath5k, e.g.

Does this (accidentally) fix it by chance?

http://patchwork.kernel.org/patch/38165/

It reloads the filters at ifup time.

-- 
Bob Copeland %% www.bobcopeland.com

Re: ath5k: monitor mode needs channel change

[Joerg Albert]

On 07/31/2009 12:05 AM, Bob Copeland wrote:
> On Thu, Jul 30, 2009 at 5:31 PM, Joerg Albert<jal2@gmx.de> wrote:
>> I currently need an extra trigger by changing the channel after
>> "ifconfig up" to see any output in monitor mode from ath5k, e.g.
> 
> Does this (accidentally) fix it by chance?
> 
> http://patchwork.kernel.org/patch/38165/
> 
> It reloads the filters at ifup time.

No, unfortunately this patch was already part of my ath5k.
I'll try to add some printk.

Re: ath5k: monitor mode needs channel change

[Bob Copeland]

On Fri, Jul 31, 2009 at 2:34 PM, Joerg Albert<jal2@gmx.de> wrote:

>> It reloads the filters at ifup time.
>
> No, unfortunately this patch was already part of my ath5k.
> I'll try to add some printk.

Ah, I was just basing that on your compat-wireless version, but
yeah w-t should have had it.

Hmm, well, probably a ath5k_reset() in add_interface would do the
trick.  Maybe there's some wrong assumption about when
configure_filter() is called.

-- 
Bob Copeland %% www.bobcopeland.com

Re: ath5k: monitor mode needs channel change

[Joerg Albert]

On 07/31/2009 08:40 PM, Bob Copeland wrote:

> Hmm, well, probably a ath5k_reset() in add_interface would do the
> trick.  Maybe there's some wrong assumption about when
> configure_filter() is called.

Adding ath5k_reset() to the end of ath5k_add_interface didn't help.

Seems like in the case of

ifconfig wlan0 down
iwconfig wlan0 mode monitor channel 1
ifconfig wlan0 up

ath5k_chan_set() is called by ath5k_config() with sc->curchan == chan
and it doesn't call ath5k_reset() - which I guess is needed
to activate the new hw rx_filter.
ath5k_config() gets parameter changed == 0xffffffff,
i.e. CONF_CHANGE_CHANNEL is flagged.

With the following

iwconfig wlan0 channel 2

ath_chan_set() gets called with
sc->curchan->center_freq != chan->center_freq and
ath5k_reset() is invoked.

Patch follows.

Regards,
Joerg.