Posting here in case anyone else is fighting this problem...
With the current stable release (23.05.x) of OpenWrt the 5 Ghz wifi channel cannot be changed from the default channel 36 with a width of 80 Mhz on my TP-Link Archer A7 router. Although selecting another channel can be done from LuCi, the router disables the 5 Ghz radio and the SSID disappears from scans. LuCi usually still shows the radio is enabled but it is not.
dmesg shows the following:
ath10k_pci 0000:00:00.0: pdev param 0 not supported by firmware
and later:
br-lan: port 2(phy0-ap0) entered disabled state
This problem exists with Openwrt 23.05.3 with kernel 5.15.150 and from what I've found on various sites, is a Linux kernel issue.
On my hardware this problem has been solved by loading the latest snapshot release with kernel 6.6.54.
Please connect to your OpenWrt device using ssh and copy the output of the following commands and post it here using the "Preformatted text </> " button:
Remember to redact passwords, MAC addresses and any public IP addresses you may have:
Have you set your country code? When no country is set it only works on the channels which are allowed everywhere, which is only the one low block of 80 MHz covering channels 36 - 48.
Looks like I posted too soon. After 3 days of running perfectly, this morning the problem occurred with the snapshot firmware installed and came back again after reboot. (The previously loaded stable release always failed immediately.)
The country code has been configured correctly and various versions of the ath10k firmware (988x, 988x-ct, & 988x-ct-full-htt) have had the same problem.
I've gone back to the stable release I was previously running to eliminate any new issues with the snapshot, and will gather and modify the files for upload today or tomorrow.
This issue turns out to be phantom DFS radar detection issue that is specific to the Archer A7, not something I was looking for because a Netgear R7000 (DD-WRT) and R7800 (OpenWRT) in the same location have never detected radar when set to 5Ghz DFS channels. Ath10k-firmware-qca988x, ath10k-firmware-qca988x-ct, and ath10k-firmware-qca988x-ct-htt have the same problem. For some reason the snapshot firmware ran fine for 3 days.
It's a pretty simple dumb AP configuration and I expect to have to ultimately replace it with a Netgear R7800, but maybe one of you will notice something.
Yes, as you have already identified, channel 100 is indeed DFS in the US (and most places around the world, too).
Yeah, it is possible that there were erroneous hits. Alternatively, something in your environment could have changed with respect to real radar hits. Or another scenario is that the other devices didn't detect the hits and/or didn't shut down the radio as they were supposed to. It's hard to know for sure, but good that you've identified that this is a DFS related issue.
With that in mind, the easy solution is to change the channel to one that is outside the DFS range.
And circling back to your issue -- was it that you were unable to select the channels, or that the radio was shutting down seemingly unexpectedly?
I've been able to select the channel from LuCi, but the radio shuts down immediately most of the time when devices connect, sometimes within seconds. Since I moved all clients off the TP-Link it hasn't shut down so I'm guessing it's confusing legitimate client transmissions with radar. A couple of articles on DFS say that it can be difficult to engineer routers that can reliably tell the difference.
My old R7000 was running in the same location for over 5 years on channel 100 without a hitch, and my R7800 has been on channel 100 on and off for days without ever detecting radar. I've found a few reports online of people experiencing similar problems after replacing other routers with TP-Link products. Hopefully the R7800 will remain stable and I'll just add another to use as a dedicated AP.
Non-DFS channels are polluted with routers Spectrum delivers with those channels preconfigured. They're probably not even in use by most people. I've been the only one using a DFS channel.
How dense is your immediate area? for example, do you live in an apartment building or other dense housing location? suburbs? etc? And what is the primary material of your home's construction?
I ask because, while it is true that the airwaves can be crowded, 5GHz signals drop off rapidly with distance and also with heavier construction materials (so brick/concrete/cinderblock/stucco/stone/plaster&lath will heavily attenuate 5GHz, whereas glass/drywall/wood will have less attenuation). That is to say that if you live in a brick house in the suburbs, 5GHz from your neighbors will probably not be a big problem. If you live in a dense apartment building with primarily wood framing and drywall, that crowded spectrum could be a real problem.
Signal strengths from the routers closest to me are almost the same as that from my Archer A7. For me an inexpensive used router is preferable to having to troubleshoot interference problems down the road.
This has less to do with the home construction (wood frame) that it does the placement of my AP vs their routers. I've moved my AP to the center of my home away from my living room while my neighbors probably have theirs where the cable enters their homes.
You still haven’t said how far your neighbors are from you, but ultimately you may find that the performance compromise of somewhat crowded spectrum is still better than dfs related shutdowns.
