On Wed, Aug 29, 2018 at 04:19:01PM -0400, Jes Sorensen wrote: > On 08/23/2018 09:36 PM, James Cameron wrote: > > G'day Carlo, Mylene, and James, > > > > Thanks for your earlier reports about RTL8723bu. Have you any more > > recent experiences you might share? > > > > I'm evaluating a sample laptop which worked fine with Windows 10, but > > not very well with Ubuntu 18.04, and kernel v4.15 or kernel v4.18.4. > > > > The laptop is by Hena, model NT16-PRO-C-E, with a wireless device on > > internal USB (0x0bda:0xb720) which loads rtl8xxxu, identifying as > > RTL8723BU. > > > > http://dev.laptop.org/~quozl/z/1ft0qv.txt (dmesg) > > > > Symptoms are low RSSI on scan, very short range, and often a failure > > to associate over a distance of two metres in a radio quiet location. > > > > Symptoms began after first power off, which suggests that device > > registers programmed by the previous operating system Windows 10 had > > not been reset by reboot into the Ubuntu 18.04 installer. The device > > worked fine in Ubuntu 18.04 before the first power off. > > > > Jes, let me know if there is anything I can do to help. > > It's been a while since I had time to look at the 8723bu support, and > rtl8xxxu doesn't have BT coexist support. I notice that your laptop does > load the bluetooth module for 8723bu which I believe fiddles with the > antenna configuration and is likely to take control of the antennas. I > suspect this is why you see low signal quality on the WiFi side. > > If you blacklist the BT module, does it work better? Thanks. No, it doesn't work any better, or worse. Method: add "blacklist btusb" to /etc/modprobe.d/blacklist.conf, regenerate initramfs, and boot. Also, a difference in symptom between cold and warm boot; * on cold boot after 15 seconds of power off, device connects but has short range, with received power at monitor of -76dBm, http://dev.laptop.org/~quozl/z/1fv7sW.txt (dmesg, cold boot, no btusb) * on warm boot with less than 5 seconds of power off, device does not connect, dmesg "authentication with xx:yy:zz:aa:bb:cc timed out", and probe request, authentication, and association packets are not seen by monitor, http://dev.laptop.org/~quozl/z/1fv8IO.txt (dmesg, warm boot, no btusb) In both cases, scan results are normal, and similar signal level. An active scan for cold boot, and a passive scan for warm boot. Monitor device is an ath9k about 30cm away; a radio quiet environment on a farm. Speculation; device registers are not being reset. Would not have been a problem for RTL8723BU on removable USB. -- James Cameron http://quozl.netrek.org/
