On Fri, Aug 22, 2014 at 2:10 AM, Tony DiCola <[email protected]> wrote: > Hey all, I've been trying to track down why my wifi dongle doesn't work > reliably on boot and think I've narrowed it down to the drivers in the > official Debian 3.8 kernel being old and buggy. > > First, the hardware I'm using: > - Rev C BeagleBone Black, running the official Debian image from here: > http://beagleboard.org/latest-images > (side question, is the 5-14-2014 image on that page really the most recent > official Debian build?)
latest "testing": http://elinux.org/Beagleboard:BeagleBoneBlack_Debian#Debian_Image_Testing_Snapshots > - Wifi dongle is an Edimax 7811Un, which is a RTL8192CU chipset. Very > popular and works perfectly with a Raspberry Pi. RTL8192CU's are crap on v3.8.x > - Yes I'm aware of the HDMI ground and power plane issue with wifi dongles, > I have the wifi dongle attached to a small USB hub that moves it away from > the BBB. > > My problem is that the wifi connection never reliably starts on boot. I > always have to log in and run ifdown wlan0 & ifup wlan0 to get it to > connect. My /etc/network/interfaces is configured in the standard way to > access my AP (exactly how I've configured Raspberry Pi's which work fine), > and for completeness the block of config looks like: > > # WiFi Example > auto wlan0 > allow-hotplug wlan0 > iface wlan0 inet dhcp > wpa-ssid "my AP name" > wpa-psk "my password" > > I ran some experiments to reboot the BBB (just using the reboot command) > multiple times and count how often the wifi connection would come up > successfully on boot. The results were not good, here's what I saw: > - With "auto wlan0" and "allow-hotplug wlan0" in /etc/network/interfaces 6 > out of 13 attempts succeeded: success rate of 46%. > - With only "auto wlan0" in /etc/network/interfces 8 out of 13 attempts > succeeded: success rate of 62%. > - With the dongle connected directly to the USB port (i.e. not through the > hub) only 4 out of 13 attempts succeeded: success rate of 31%. > > I did all I could to find any information from dmesg and syslog for the > failed attempts, but there's no info there. When the connection works on > boot I see messages about the RTL8192CU module and then the wlan connection > coming up. When the connection does not work I see the same messages about > the RTL8192CU module but none of the wlan connection messages. There are no > errors or failures at all in the log. It really feels like a timing or > internal issue with the RTL module. If there is some other log I should be > looking at please let me know and I will check it out. > > For comparison I ran the same test with the same wifi adapter on a Raspberry > Pi running the latest Raspbian OS image. It worked fine and brought the > wifi connection up all 13 times, success rate of 100%. > > At this point I was really confused why the BBB could not reliably bring up > a wifi connection at boot. Looking a little closer the big obvious > difference between the BBB and Pi is the kernel version. On the Pi it's > using kernel 3.15.3 whereas the BBB is running the 3.8 kernel. Looking at > the RTL8192CU source on kernel.org I can't find the 3.8 kernel source, but > at least comparing the 3.10 kernel to mainline there are quite a few fixes > in the more recent kernels but not in the older ones. > > To really confirm it was the 3.8 kernel I used Robert Nelson's upgrade > script to take my BBB to the 3.15.10-bone7 kernel (script from here > https://rcn-ee.net/deb/wheezy-armhf/v3.15.10-bone7/). After upgrading the > kernel I ran the same reboot test and surprise, surprise the BBB brought up > the wifi connection 13 out of 13 times, success rate of 100%. 3.15.x has much better usb support over v3.8.x > > So long story short it seems like at least for Realtek adapters the official > Debian image's 3.8 kernel has some serious issues. I'm curious is this a > known issue or something being worked on right now? > > I noticed on the BBB kernel github there was just recently a commit > yesterday to add perhaps a backport of later RTL8192CU drivers to the 3.8 > kernel (looking at > https://github.com/beagleboard/linux/tree/3.8/drivers/net/wireless/rtl8192cu > ). Is this true that later RTL wifi drivers are being ported back to the > 3.8 kernel? > > Finally, is there any suggestion for what folks who use the RTL8192CU or > other RTL wifi adapters should do to use them right now on the BBB? Is the > 3.15.10-bone7 kernel stable enough for normal use? (like using GPIO, loading > and unloading device tree overlays, etc) overlays = v3.8.x Regards, -- Robert Nelson http://www.rcn-ee.com/ -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
