What is current state of DBDC support?

[VA1DER]

I am trying and failing to get DBDC to work on my MT7615 device. I have searched and read through multiple issues and am still unsure of what the level of support is. It it still considered an experimental feature?

So far I can almost get it to work by following an abbreviated set of steps found here and here:

1. Change settings in /etc/config/wireless from "option path" to "option phy" for each radio
2. wifi down
3. echo 1 > /sys/kernel/debug/ieee80211/phy0/mt76/dbdc
4. wifi up

Is it possible to have DBDC turned on at boot without the poke in step 3?

[lleachii]

@VA1DER

Is it possible to have DBDC turned on at boot without the poke in step 3?

I'm not sure what "poke" means - unless you're referring to purposely enabling a debug option.

Just set it as a startup command or place in sysctrl.

[VA1DER]

@lleachii

I'm not sure what "poke" means

It's a programming term from long ago. When you wanted to activate some obscure and not well (or at all) documented feature, you "poked" a value into a memory location. C64, Apple][, Trash 80, that era. I'm showing my age.

@lleachii

startup command

I get that. I'm just trying to find out what the intended behaviour and current state is right now. Some places suggest it's a test-only feature, some suggest it's doable right from LuCI, no "pokes" required. Even turning it on manually I can still only get it to only partially work, and I'm not sure if I'm not doing things right, if it's my hardware (which is a bit of a kitbash), or the feature is not fully implemented.

Not asking anyone to solve my issues. But I would like to know if anyone else has it working even partially, and if they do to maybe start collecting some configs to see what the common denominator is. Then I can write up something in the Wiki to help document where the feature is at.

To that end...

What works (for me):

• One "radio" in STA mode connecting as a client to another router
• The other "radio" in AP mode successfully creates an SSID that devices can at least see

Issues:

• Activating the feature (with echo 1 > /sys/kernel/debug/ieee80211/phy0/mt76/dbdc) returns an error, though it does appear to activate the second PHY
• Devices can connect to the AP radio, and are successfully associated, but then immediately dissociated.
• Both PHY0 and PHY1 appear to support both 2.4G and 5G, which for the 7615 is definitely not the case.
• Device lights not working properly.

Looking for anyone else using the feature in OpenWrt and what works for you

[VA1DER]

I just retested DBDC and mostly got it to work. I tested it in a wi-fi relayd repeater configuration, which might explain why it still seemed a bit glitchy. But at least it seems to mainly work. The procedure I used is essentially unchanged from in the lead post, but I'll detail it here:

What I did:

1. Changed option path to option phy in /etc/config/wireless
2. Ensure that radio0 (phy0) is set to 2g and radio1 (phy1) is set to 5g
3. Add the following to /etc/rc.local

# Turn on DBDC
(
  sleep 10
  wifi down
  sleep 3
  echo 1 > /sys/kernel/debug/ieee80211/phy0/mt76/dbdc
  sleep 3
  wifi up
) &
  

Here is my /etc/config/wireless to illustrate step 1:

config wifi-device 'radio0'
        option type 'mac80211'
        option phy 'phy0'
        option channel '11'
        option band '2g'
        option htmode 'HT40'

config wifi-iface 'default_radio0'
        option device 'radio0'
        option network 'lan'
        option mode 'ap'
        option ssid 'DBDCTest'
        option encryption 'psk2'
        option key 'DBDCTestKEY'

config wifi-device 'radio1'
        option type 'mac80211'
        option phy 'phy1'
        option band '5g'
        option htmode 'VHT160'
        option channel '153'

config wifi-iface 'wifinet1'
        option device 'radio1'
        option mode 'sta'
        option network 'wlan'
        option ssid 'MAINSSID'
        option encryption 'psk2'
        option key 'MAINSSIDKEY'
        option disassoc_low_ack '0'

What doesn't work for me (and can use advice on if anyone has some):

• Still can't get the card to boot up IN DBDC mode.
• In wireless bridge/repeater mode it's a bit glitchy, where accessing the device's own IP address is hit or miss.
• Luci thinks that both virtual radios support both 2.4g and 5g. This is not the case. You have to use PHY0 for 2.4 and PHY1 for 5g or it won't work.

All the above tested with an AsiaRF MT7615N card in a BPI-R2 based device.