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RE: rt2800usb firmware rt2870.bin 0.36 not scanning

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I wrote:
> I wrote:
> > Xose Vazquez Perez wrote:
> > > Craig McQueen wrote:
> > >
> > > > I have a D-Link DWA-140 USB Wi-Fi device which is rt2800 based
> > > > (5392 chipset). I'm trying to use it on a BeagleBone Black based
> > > > system with 3.14.x kernel built with Yocto. We're using ConnMan
> > > > 1.30 at the
> > moment.
> > >
> > > Try it with a _desktop x86_64 distribution_ , with a *recent kernel*
> > > as
> > > Fedora: (WORK is gnome)
> > > https://alt.fedoraproject.org/pub/alt/live-respins/
> >
> > Hmm, that is non-trivial but I may try it.
> >
> > For now, I'll also try a 4.4.6 kernel running on a BeagleBone Black
> > (with a USB hub to work around another issue with the rt2800usb driver
> > crashing as described in another e-mail).
> >
> > > > We've been finding some instabilities with it periodically
> > > > disconnecting from some networks. So we tried upgrading the
> > > > firmware file rt2870.bin from version 0.29 to 0.36. That seems to
> > > > be more stable with the network. However, we're finding that it
> > > > initially doesn't connect, until the Wi-Fi has been disabled and then re-
> enabled. '
> > > scan wifi'
> > > > and 'iwlist scan' don't return anything until Wi-Fi has been
> > > > disabled and then re-enabled.
> > >
> > > Don't use any wrapper(NM, ConnMan, wicd, ...), usually are buggy.
> > > You should use raw commands "iw" and "wpa_supplicant". Hints:
> > > https://wireless.wiki.kernel.org/en/users/documentation/iw and
> > > wpa_supplicant always running with "-Dnl80211"
> >
> > Okay, I've stripped down the system so ConnMan, udev rules aren't
> running.
> >
> > On all systems, after plugging in the device, I have to issue:
> >
> >     ip link set wlan0 up
> >
> > After this, I try to do a scan:
> >
> >     iw dev wlan0 scan
> >
> > On kernel 4.4.6, with firmware 0.36, it works fine (lists APs it
> > finds). On kernel 3.14.x, with firmware 0.29, it works fine. But on
> > kernel 3.14.x, with firmware 0.36, it returns nothing. But then, if I do this:
> >
> >     ip link set wlan0 down
> >     ip link set wlan0 up
> >     iw dev wlan0 scan
> >
> > Then it works fine.
> >
> > So, the question is, why does firmware 0.36 with kernel 3.14.x not
> > work until I've made the interface go up, then down, and then up again?
> 
> I've managed to build, using Yocto, kernel 4.4.12 for BeagleBone. When I run
> it, it has the same problem. That's different from the Ubuntu 16.04 for
> BeagleBone using 4.4.6 kernel.
> 
> With my Yocto build, it had a different version of the 'ip' and 'iw' commands.
> So I tried copying the Ubuntu versions, but that didn't make a difference. I
> tried using the Yocto built 4.4.12 kernel with the Ubuntu root filesystem, but
> it halted during the boot process (don't know why). My best guess is that
> there's some kernel config difference that makes a difference, but there are
> many differences, so I'm not sure which one it might be.
> 
> I'm not sure at this point how to narrow it down to the root cause. Any
> advice?
> 
> I wonder if maybe there's a race condition in the rt2800usb driver between
> loading the rt2870.bin firmware and doing the interface-up initialisation.
> Normally the firmware loads at the point of doing the 'iw link set wlan0 up'
> command. Is there a way to force the firmware to load before that
> command?

I've got two rt2800 devices:

* D-Link DWA-140 with RT chipset 5392, rev 0223, and RF chipset 5372
* Edup EP-N8537 with RT chipset 5390, rev 0502, and RF chipset 5370

I've also found that with the Yocto-built 4.4.12 kernel, this no-scan issue only happens to the Edup with the 5390 chipset. The D-Link is fine.

With the Ubuntu 4.4.6 kernel, both devices work fine, without this no-scan problem.

I'm having trouble narrowing it down further, since these varying circumstances don't obviously point towards a root cause. Somehow it seems to be dependent on a combination of kernel configuration, the device's chipset, and which firmware is loaded on the device. Unless it's just a marginal timing issue due to some race condition. But at this point I'm not sure where to look.

Any advice would be much appreciated; I'm not sure where to look next since I'm not familiar with the USB and Wi-Fi systems of the kernel.

Where might I find rt2800 experts/maintainers these days who might be able to give some advice on this?

Thanks,
Craig McQueen

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