I was on my way to open a new bug report about the subject of this topic, but there are at least two bugs about this issue already reported and still open (one of them from 2017):
So instead of open a new bug report I decided to share my findings here (just in case someone has an workaround) and later I will update both bugs above with the details below.
I am reporting this issue observed on a TP-Link Archer C6 3.2 (MT7621 + MT7603EN 2.4Ghz + MT7613BEN 5Ghz) running a snapshot build (r17525-a46fa5c3a7).
The issue seems to be with the M76 driver which is completely ignoring the "TX Power" set via LuCI and UCI. I am saying the issue seems to be the Wi-Fi driver because
iwinfo everything seems to be OK.
See the example below. I've set the TX Power to 0dbm for testing purposes, and
iwinfo correctly show the value I've configured:
root@ap2:~# uci show wireless.radio1 wireless.radio1=wifi-device wireless.radio1.type='mac80211' wireless.radio1.path='1e140000.pcie/pci0000:00/0000:00:01.0/0000:02:00.0' wireless.radio1.band='5g' wireless.radio1.htmode='VHT80' wireless.radio1.country='PA' wireless.radio1.channel='100' wireless.radio1.cell_density='0' wireless.radio1.txpower='0' root@ap2:~# iwinfo wlan1 info wlan1 ESSID: "dshome5ghz-tst" Access Point: xx:xx:xx:xx:C8:40 Mode: Master Channel: 100 (5.500 GHz) Center Channel 1: 106 2: unknown Tx-Power: 0 dBm Link Quality: 24/70 Signal: -86 dBm Noise: -92 dBm Bit Rate: 234.0 MBit/s Encryption: WPA2 PSK (CCMP) Type: nl80211 HW Mode(s): 802.11nac Hardware: 14C3:7663 14C3:7663 [MediaTek MT7613BE] TX power offset: none Frequency offset: none Supports VAPs: yes PHY name: phy1 root@ap2:~#
However the 0dBm configuration above has no effect on TX Power at all.
With TX Power configured at 0 dBm for the 5Ghz radio in the example above, Wi-Fi signal should be very weak and should work only on the same room and close to the access point.
However as seen below the signal strength measured with a laptop located about 10 meters away from the access point with a brick wall between the laptop and the access point and the wi-if signal strength is still strong. This is the same level as if TX Power is at 22dBm (driver default level), so in fact the TX Power configuration is not working:
ubuntu@ubuntu:~$ iwconfig wlp2s0 wlp2s0 IEEE 802.11 ESSID:"dshome5ghz-tst" Mode:Managed Frequency:5.5 GHz Access Point: xx:xx:xx:xx:C8:40 Bit Rate=26 Mb/s Tx-Power=22 dBm Retry short limit:7 RTS thr:off Fragment thr:off Power Management:on Link Quality=42/70 Signal level=-68 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:30 Missed beacon:0
I've experimented other TX Power levels, and none configuration has any effect on OpenWRT TX Power. I am not sure if this is an OpenWRT bug or if it is in fact a MT76 driver issue to be reported upstream by OpenWRT devs.