Trouble with bluetooth intermittently working

Question

Further to the problems I experienced with my touchpad, I am now encountering issues with bluetooth. Everything was working fine, but on my most recent reboot bluetooth now seems to have totally stopped working.

From my searching around various forums, a weird thing is that the output of rfkill list all is only this:

0: phy0: Wireless LAN
    Soft blocked: no
    Hard blocked: no

lsmod | grep ath outputs:

ath3k                  20480  0 
ath9k                 147456  0 
ath9k_common           32768  1 ath9k
ath9k_hw              479232  2 ath9k_common,ath9k
ath                    32768  3 ath9k_common,ath9k,ath9k_hw
mac80211              753664  1 ath9k
cfg80211              561152  5 wl,ath,ath9k_common,ath9k,mac80211
bluetooth             516096  14 bnep,ath3k,btbcm,btusb,rfcomm,btintel

bluetooth outputs:

bluetooth = none (no device)

But before the last reboot, it was working great. I had paired a keyboard and mouse. In System Settings, everything on the Bluetooth page is greyed out. I can't even try to turn it on and the device list is now blank.

Any thoughts or assistance much appreciated.

Update

I'm feeling slightly closer, the output of dmesg | grep -i blue is:

[    3.925283] Bluetooth: Core ver 2.20
[    3.925305] Bluetooth: HCI device and connection manager initialized
[    3.925309] Bluetooth: HCI socket layer initialized
[    3.925312] Bluetooth: L2CAP socket layer initialized
[    3.925318] Bluetooth: SCO socket layer initialized
[    3.946202] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[    3.946205] Bluetooth: BNEP filters: protocol multicast
[    3.946209] Bluetooth: BNEP socket layer initialized
[    3.952299] Bluetooth: RFCOMM TTY layer initialized
[    3.952328] Bluetooth: RFCOMM socket layer initialized
[    3.952333] Bluetooth: RFCOMM ver 1.11
[    5.271147] Bluetooth: Patch file not found ar3k/AthrBT_0x11020100.dfu
[    5.271149] Bluetooth: Loading patch file failed

It seems to be the same error as here, but a different bug causing it.

Answer 1

I have finally managed to sort this out by reading through a number of bug reports and eventually getting some help from a friendly good Samaritan. If anyone comes across this issue, here's what you need to do.

First, update your kernel to the latest long-term support:

sudo apt-get install linux-generic-lts-wily

Then, download these two firmware files:

https://bugs.launchpad.net/ubuntu/+source/linux-lts-utopic/+bug/1462614/+attachment/4453553/+files/AthrBT_0x11020100.dfu

https://bugs.launchpad.net/ubuntu/+source/linux-lts-utopic/+bug/1462614/+attachment/4453554/+files/ramps_0x11020100_40.dfu

And put them in: /lib/firmware/ar3k/

Reboot, and then rejoice!

So delighted to finally have everything working properly on my Librem 13 with Elementary OS! :)