How to fix WLAN issues with Debian Linux and the Acer Aspire 5

I've recently bought the Acer Aspire 5 A515-52G-53PU and experienced issues with the Wifi. This blog entry is for anyone with the same issues.

After some days I've experienced that my system ignored touch input with a frequency of 1 second. sudo dmesg -c exposed this:

[  374.733298] iwlwifi 0000:00:14.3: Microcode SW error detected. Restarting 0x0.
[  374.733372] iwlwifi 0000:00:14.3: Start IWL Error Log Dump:
[  374.733374] iwlwifi 0000:00:14.3: Status: 0x00000100, count: 6
[  374.733375] iwlwifi 0000:00:14.3: Loaded firmware version: 38.755cfdd8.0
[  374.733377] iwlwifi 0000:00:14.3: 0x00000071 | ADVANCED_SYSASSERT         
[  374.733378] iwlwifi 0000:00:14.3: 0x0080A210 | trm_hw_status0
[  374.733380] iwlwifi 0000:00:14.3: 0x00000000 | trm_hw_status1
[  374.733381] iwlwifi 0000:00:14.3: 0x00454EAA | branchlink2
[  374.733382] iwlwifi 0000:00:14.3: 0x0045E8C2 | interruptlink1
[  374.733383] iwlwifi 0000:00:14.3: 0x0045E8C2 | interruptlink2
[  374.733384] iwlwifi 0000:00:14.3: 0x00000000 | data1
[  374.733385] iwlwifi 0000:00:14.3: 0x00001000 | data2
[  374.733386] iwlwifi 0000:00:14.3: 0xF0000008 | data3
[  374.733387] iwlwifi 0000:00:14.3: 0xFFF4F839 | beacon time
[  374.733388] iwlwifi 0000:00:14.3: 0x104CA603 | tsf low
[  374.733389] iwlwifi 0000:00:14.3: 0x000001E9 | tsf hi
[  374.733390] iwlwifi 0000:00:14.3: 0x00000000 | time gp1
[  374.733391] iwlwifi 0000:00:14.3: 0x003CEEE8 | time gp2
[  374.733393] iwlwifi 0000:00:14.3: 0x00000001 | uCode revision type
[  374.733394] iwlwifi 0000:00:14.3: 0x00000026 | uCode version major
[  374.733395] iwlwifi 0000:00:14.3: 0x755CFDD8 | uCode version minor
[  374.733396] iwlwifi 0000:00:14.3: 0x00000312 | hw version
[  374.733397] iwlwifi 0000:00:14.3: 0x18C89008 | board version
[  374.733398] iwlwifi 0000:00:14.3: 0x0061019C | hcmd
[  374.733399] iwlwifi 0000:00:14.3: 0x24022000 | isr0
[  374.733400] iwlwifi 0000:00:14.3: 0x01800000 | isr1
[  374.733401] iwlwifi 0000:00:14.3: 0x08001802 | isr2
[  374.733402] iwlwifi 0000:00:14.3: 0x00417CC0 | isr3
[  374.733403] iwlwifi 0000:00:14.3: 0x00000000 | isr4
[  374.733404] iwlwifi 0000:00:14.3: 0x0061019C | last cmd Id
[  374.733405] iwlwifi 0000:00:14.3: 0x00000000 | wait_event
[  374.733406] iwlwifi 0000:00:14.3: 0x00000080 | l2p_control
[  374.733407] iwlwifi 0000:00:14.3: 0x00010034 | l2p_duration
[  374.733408] iwlwifi 0000:00:14.3: 0x0000003F | l2p_mhvalid
[  374.733410] iwlwifi 0000:00:14.3: 0x000000CE | l2p_addr_match
[  374.733411] iwlwifi 0000:00:14.3: 0x0000000D | lmpm_pmg_sel
[  374.733412] iwlwifi 0000:00:14.3: 0x08081115 | timestamp
[  374.733413] iwlwifi 0000:00:14.3: 0x0034D800 | flow_handler
[  374.733447] iwlwifi 0000:00:14.3: Start IWL Error Log Dump:
[  374.733448] iwlwifi 0000:00:14.3: Status: 0x00000100, count: 7
[  374.733449] iwlwifi 0000:00:14.3: 0x00101208 | ADVANCED_SYSASSERT
[  374.733450] iwlwifi 0000:00:14.3: 0x00000000 | umac branchlink1
[  374.733452] iwlwifi 0000:00:14.3: 0xC0087C88 | umac branchlink2
[  374.733453] iwlwifi 0000:00:14.3: 0xC008462C | umac interruptlink1
[  374.733454] iwlwifi 0000:00:14.3: 0x00000000 | umac interruptlink2
[  374.733455] iwlwifi 0000:00:14.3: 0x00000001 | umac data1
[  374.733456] iwlwifi 0000:00:14.3: 0x000003FF | umac data2
[  374.733457] iwlwifi 0000:00:14.3: 0xDEADBEEF | umac data3
[  374.733458] iwlwifi 0000:00:14.3: 0x00000026 | umac major
[  374.733459] iwlwifi 0000:00:14.3: 0x755CFDD8 | umac minor
[  374.733460] iwlwifi 0000:00:14.3: 0xC08875AC | frame pointer
[  374.733461] iwlwifi 0000:00:14.3: 0xC08875AC | stack pointer
[  374.733462] iwlwifi 0000:00:14.3: 0x0061019C | last host cmd
[  374.733463] iwlwifi 0000:00:14.3: 0x00000000 | isr status reg
[  374.733466] ieee80211 phy2: Hardware restart was requested
[  375.183415] iwlwifi 0000:00:14.3: BIOS contains WGDS but no WRDS

First I tried updating the firmware driver for iwlwifi from the sid repository as I thought this would help. But sadly it didn't...

According to this post I should try out some module options and this is what helped me:

$ cat /etc/modprobe.d/iwlwifi.conf
options iwlwifi 11n_disable=1

According to inxi my card is this:

Network:   Device-1: Intel Cannon Point-LP CNVi [Wireless-AC] driver: iwlwifi v: kernel port: 5000 bus ID: 00:14.3
           chip ID: 8086:9df0
           IF: wlp0s20f3 state: up mac: <filter>

Maybe this also means that 802.11n does not work anymore but this is ok for me as I don't use WLAN for bulk data transfer.