Wifi extremely slow and sometimes it doesn't work at all.

Some additional info:

sudo lshw -class network

*-network
       description: Wireless interface
       product: BCM43602 802.11ac Wireless LAN SoC
       vendor: Broadcom Limited
       physical id: 0
       bus info: pci@0000:02:00.0
       logical name: wlp2s0
       version: 01
       serial: 40:49:0f:fe:d2:81
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=brcmfmac driverversion=7.35.177.61 firmware=01-ea662a8c ip=192.168.1.8 latency=0 multicast=yes wireless=IEEE 802.11
       resources: irq:137 memory:dd800000-dd807fff memory:dd400000-dd7fffff

lspci

00:00.0 Host bridge: Intel Corporation Skylake Host Bridge/DRAM Registers (rev 07)
00:01.0 PCI bridge: Intel Corporation Skylake PCIe Controller (x16) (rev 07)
00:02.0 VGA compatible controller: Intel Corporation HD Graphics 530 (rev 06)
00:04.0 Signal processing controller: Intel Corporation Skylake Processor Thermal Subsystem (rev 07)
00:14.0 USB controller: Intel Corporation Sunrise Point-H USB 3.0 xHCI Controller (rev 31)
00:14.2 Signal processing controller: Intel Corporation Sunrise Point-H Thermal subsystem (rev 31)
00:15.0 Signal processing controller: Intel Corporation Sunrise Point-H Serial IO I2C Controller #0 (rev 31)
00:15.1 Signal processing controller: Intel Corporation Sunrise Point-H Serial IO I2C Controller #1 (rev 31)
00:16.0 Communication controller: Intel Corporation Sunrise Point-H CSME HECI #1 (rev 31)
00:17.0 SATA controller: Intel Corporation Sunrise Point-H SATA Controller [AHCI mode] (rev 31)
00:1c.0 PCI bridge: Intel Corporation Sunrise Point-H PCI Express Root Port #1 (rev f1)
00:1c.1 PCI bridge: Intel Corporation Sunrise Point-H PCI Express Root Port #2 (rev f1)
00:1d.0 PCI bridge: Intel Corporation Sunrise Point-H PCI Express Root Port #9 (rev f1)
00:1d.4 PCI bridge: Intel Corporation Sunrise Point-H PCI Express Root Port #13 (rev f1)
00:1d.6 PCI bridge: Intel Corporation Sunrise Point-H PCI Express Root Port #15 (rev f1)
00:1f.0 ISA bridge: Intel Corporation Sunrise Point-H LPC Controller (rev 31)
00:1f.2 Memory controller: Intel Corporation Sunrise Point-H PMC (rev 31)
00:1f.3 Audio device: Intel Corporation Sunrise Point-H HD Audio (rev 31)
00:1f.4 SMBus: Intel Corporation Sunrise Point-H SMBus (rev 31)
01:00.0 3D controller: NVIDIA Corporation GM107M [GeForce GTX 960M] (rev a2)
02:00.0 Network controller: Broadcom Limited BCM43602 802.11ac Wireless LAN SoC (rev 01)
03:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS525A PCI Express Card Reader (rev 01)
04:00.0 Non-Volatile memory controller: Toshiba America Info Systems Device 0115 (rev 01)

dmesg | grep brcmf

[ 4.752375] usbcore: registered new interface driver brcmfmac
[ 4.752448] brcmfmac 0000:02:00.0: enabling device (0000 -> 0002)
[ 4.940064] brcmfmac 0000:02:00.0: Direct firmware load for brcm/brcmfmac43602-pcie.txt failed with error -2
[ 5.459355] brcmf_c_preinit_dcmds: Firmware version = wl0: Nov 10 2015 06:38:10 version 7.35.177.61 (r598657) FWID 01-ea662a8c
[ 5.493897] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 5.501130] brcmfmac 0000:02:00.0 wlp2s0: renamed from wlan0
[ 24.223149] brcmf_inetaddr_changed: fail to get arp ip table err:-23
[ 641.851234] brcmf_inetaddr_changed: fail to get arp ip table err:-23
[ 641.851423] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 650.081531] brcmf_inetaddr_changed: fail to get arp ip table err:-23

Please let me know if you need further info.

Thanks

Have you tried rebooting your router? Leave it off for 30 seconds then power it back on, then reboot your PC.

So far I have rebooted the access point and the laptop several times.
I'll reboot the router also and I'll let you know.
(Not very optimistic though, because every other device wired / wireless works fine.)

I rebooted everything (rooter / access point / laptop).
The pages load significantly faster but the speed-test gives me around 9 MBbps while I have 21 MBbs on my mobile phone side by side both using Ooklas speedtest to the same server.

I just noticed something else.
If I bring my laptop literally next to the access point I'm getting all the speed my line can give me.
It seems like the driver does not set the card to the needed power.
(I just remind than if I boot to windows I have full speed.)

If you run:

iw

Do you get some output or just "command not found". If you have the command then run:

iw wlp2s0 set power_save off

Does it help?

No it didn't.
After I executed the command I disconnected and connected again.
Ookla's speedtest gave me D: 0.64Mbps, U: 2.03Mbps.
5 mins later D:2.44, U:2.02.
Practically zero download but my upload is my line's limit.

BTW, here is my iwconfig

wlp2s0 IEEE 802.11 ESSID:"Pontikotripa"
          Mode:Managed Frequency:5.24 GHz Access Point: 02:18:1A:79:C6:93
          Bit Rate=81 Mb/s Tx-Power=31 dBm
          Retry short limit:7 RTS thr:off Fragment thr:off
          Power Management:off
          Link Quality=33/70 Signal level=-77 dBm
          Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
          Tx excessive retries:1234 Invalid misc:0 Missed beacon:0

Also I have an Ubuntu server on my LAN, in case you want to run any local speed test.

Today I used my previous dlink router as a Wireless Repeater to workaround the issue. (although my default access point is 5 meter away with just a wall between).

My old laptop (ubuntu with iwlwifi driver) was able to connect just fine.
My current laptop (with the brcmfmac driver) was asking for password again and again.
This happened a couple of times with my original access point.

In the meantime I was getting these on dmesg:

[ 28.272842] brcmf_inetaddr_changed: fail to get arp ip table err:-23
[ 33.613932] systemd[1]: Failed to add watch on /: too many watches
[ 33.613939] systemd[1]: systemd-ask-password-wall.path: Failed to enter waiting state: No space left on device
[ 38.132671] brcmf_inetaddr_changed: fail to get arp ip table err:-23
[ 38.132705] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 64.517889] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 91.330526] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 109.429970] IPv6: ADDRCONF(NETDEV_UP): wlp2s0: link is not ready
[ 118.157095] IPv6: ADDRCONF(NETDEV_CHANGE): wlp2s0: link becomes ready
[ 139.557062] brcmf_inetaddr_changed: fail to get arp ip table err:-23
[ 165.832222] brcmf_inetaddr_changed: fail to get arp ip table err:-23
[ 165.832316] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 173.799848] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 205.993099] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 218.532265] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 225.897247] brcmf_inetaddr_changed: fail to get arp ip table err:-23
[ 247.402019] brcmf_inetaddr_changed: fail to get arp ip table err:-23
[ 247.402128] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 249.376869] IPv6: ADDRCONF(NETDEV_UP): wlp2s0: link is not ready
[ 299.551857] IPv6: ADDRCONF(NETDEV_CHANGE): wlp2s0: link becomes ready
[ 318.091724] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 353.162717] IPv6: ADDRCONF(NETDEV_UP): wlp2s0: link is not ready
[ 361.300640] IPv6: ADDRCONF(NETDEV_CHANGE): wlp2s0: link becomes ready
[ 362.132642] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 393.994576] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 473.521162] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[ 498.019750] brcmf_inetaddr_changed: fail to get arp ip table err:-23

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