I have a laptop running Debian Jessie with Intel Wireless-N 7265 BGN adapter. Mine looks like the one on the right, with an antenna cable going to the right-most socket.
dmesg I'm using WLAN firmware
iwlwifi-7265-16.ucode and BT firmware
ibt-hw-37.8.10-fw-22.214.171.124.d.bseq, which I have installed from Jessie-backports. As far as I understand, Wifi / Bluetooth coexistence is possible and enabled:
$ sudo modinfo iwlwifi
parm: bt_coex_active:enable wifi/bt co-exist (default: enable) (bool)
$ cat /sys/module/iwlwifi/parameters/bt_coex_active
Both Wifi and Bluetooth work separately, however, when I try to activate them at the same time, I lose Wifi connectivity. The laptop disconnects from a network if it was connected, and scanning for networks yields no results unless I disable Bluetooth. Once Bluetooth is disabled, I'm able to reconnect to Wifi again.
What could be the reason for this? Is there a particular firmware I could use to get Wifi and Bluetooth work together? Or do I have the bad kind of adaptor, and upgrading it would solve my issue? Would it help to get a second antenna connected? I don't have one, but I would consider ordering / making one if that is known to help.
EDIT: Here's what happens on my system starting from a fresh reboot:
dmesg | grep iwlwifi > dmesg_iwlwifi
dmesg | grep -i blue > dmesg_bluetooth
sudo modinfo iwlwifi | grep -v alias > modinfo_iwlwifi
sudo modinfo btintel > modinfo_btintel
Linux hostname 4.6.0-0.bpo.1-686-pae #1 SMP Debian 4.6.4-1~bpo8+1 (2016-08-11) i686 GNU/Linux
EDIT2: Things I have tried.
cfg80211_disable_40mhz_24ghzto "Y" - no visible changes
bt_coex_activeto "N" - make things worse: WiFi stops working altogether, BT still works fine
- upgrading firmware to the latest version as described here - no visible changes
disable_11acto "Y" and
11n_disableto 1 - no visible changes
Final edit: we went to see some friends this weekend, and when I wanted to show them my issue, I discovered that I could stay connected to their router while using BT. There is a drop in connection speed when BT is in use, but this is to be expected AFAIK. I'm not sure if my question will be of any use to anyone, but just in case: the router I had the issue with was a german FritzBox configured to 2.4 GHz, channel 6. Since I don't own that router, I can't really fiddle with it to investigate.