I wrote: > 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. Actually, I was wrong. With the 3.14.x Yocto-built kernel, this no-scan issue only happens with the Edup with the 5390 chipset, and the D-Link is fine. But further testing with the 4.4.12 Yocto-built kernel shows that it randomly sometimes happens and sometimes doesn't with either the Edup or D-Link devices. That's especially interesting, because it suggests that there may be a race condition happening during the driver initialisation code (called from rt2x00lib_start()). At first I thought it was a race condition between the calls to rt2x00lib_load_firmware() and rt2x00lib_initialize(), but adding a time delay between those calls didn't help. I'm wondering what the difference is between the two chipsets, so that the problem happens more on one chipset than the other. But not exclusively, as I mentioned above, so again, this points to a marginal timing issue that affects one more than the other. > With the Ubuntu 4.4.6 kernel, both devices work fine, without this no-scan > problem. > ... -- Craig McQueen ��.n��������+%������w��{.n�����{���zW����ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
