Re: [rt2x00-users] rt2500usb broken since 2.6.29

[Ondrej Zary <linux@rainbow-software.org>]

On Friday 19 March 2010 16:01:47 Ondrej Zary wrote:
> On Thursday 18 March 2010, Luis Correia wrote:
> > Hi,
> >
> > On Thu, Mar 18, 2010 at 22:04, Ondrej Zary <linux@rainbow-software.org>
>
> wrote:
> > > On Thursday 18 March 2010 22:51:18 Luis Correia wrote:
> > >> Hi,
> > >>
> > >> On Thu, Mar 18, 2010 at 21:46, Ondrej Zary
> > >
> > > <linux@rainbow-software.org>wrote:
> > >> > Hello,
> > >> > rt2500usb is broken since kernel 2.6.29. It has been discussed
> > >> > before but never solved:
> > >> > http://rt2x00.serialmonkey.com/phpBB/viewtopic.php?f=4&t=4834
> > >> > https://bugzilla.redhat.com/show_bug.cgi?id=484888
> > >> >
> > >> > I have Asus WL-167G and it really does not work. Scanning works,
> > >> > association
> > >> > too but no packets can be sent (looks like receive works because
> > >> > tcpdump shows packets from other machines). DHCP fails (No
> > >> > DHCPOFFERS received).
> > >> >
> > >> > The problem is caused by this patch:
> > >> >
> > >> > rt2x00: Implement HW encryption (rt2500usb)
> > >> >
> > >> > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=c
> > >> >om mit ;h=dddfb478b26e29a2b47f655ec219e743b8111015
> > >> >
> > >> > Removing it from 2.6.29 restores the functionality.
> > >> >
> > >> > --
> > >> > Ondrej Zary
> > >>
> > >> you can prevent hardware encryption by supplying "nohwcrypt=1" to the
> > >> driver.
> > >> (modinfo rt2500usb)
> > >
> > > That did not work. Maybe that was because I just unloaded the rt2500usb
> > > module and loaded it again with nohwcrypt=1 without rebooting the
> > > machine. Then I removed the HW encryption, recompiled and reloaded and
> > > it did not work either. It started to work only after reboot.
> >
> > did you actually remove the usb module and unloaded the module as well?
> >
> > you then need to load the module with the option, wait one sec and
> > then plug the device back in.
> >
> > > Does the HW encryption really work with any rt2500usb hardware? How can
> > > I help to fix it? Or maybe it should be disabled by default.
> >
> > I think the HW encription did work in the past, but I'm unsure of the
> > proper timeline.
>
> HW encryption was added in 2.6.29 and it does not work there. In 2.6.30,
> the driver is broken even more - it does not work even with HW encryption
> disabled. I'm going to bisect it.

Bisection revealed this commit:
ac7f9cfa2c3b810e0adfb889ad407a8c79a84dbe
cfg80211: accept no-op interface mode changes

Removing it from 2.6.30 (and disabling HW encryption) makes rt2500usb work in 
2.6.30. There are more changes to that code in next kernels so the patch 
cannot be removed from newer kernels. However, disabling it (by changing "if 
(change)" to "if (1)" in net/wireless/nl80211.c) and disabling HW encryption 
makes rt2500usb work even in 2.6.34-rc1.

There seems to be another (third!) problem. With 2.6.29, DHCP works on the 
first DHCPDISCOVER. With 2.6.30, it takes two to three DHCPDISCOVERs to get a 
reply. With 2.6.34-rc1, it takes three to five. After one reboot with 
2.6.34-rc1, it did not work at all with this in log:
phy0 -> rt2500usb_set_device_state: Error - Device failed to enter state 3 
(-16).

-- 
Ondrej Zary