[openwrt/openwrt] ramips: work around duplicate MAC address on U6 Lite

[LEDE Commits]

blocktrron pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/b1d483b865d0a6110d95a0638903a73c7354865a

commit b1d483b865d0a6110d95a0638903a73c7354865a
Author: David Bauer <mail at david-bauer.net>
AuthorDate: Sat Dec 18 00:33:57 2021 +0100

    ramips: work around duplicate MAC address on U6 Lite
    
    The UniFi 6 Lite has two MAC addresses for the 2.4 and 5GHz radio in
    it's EEPROM partition.
    
    On my unit these are
    
    F4 92 BF A0 BB 6F
    F6 92 BF A0 BB 6F
    
    The problem with these is that mac80211 increases the first octet by
    2, which leads to conflicting MAC addresses between radios.
    
    Work around this problem for now by increasing the last octet by 1 on
    the 5 GHz radio.
    
    Ubiquiti increases the last octet by 2 for each subsequent VAP created
    per radio. Ideally we should do the same, however this functionality is
    currently lacking from mac80211.
    
    Signed-off-by: David Bauer <mail at david-bauer.net>
---
 target/linux/ramips/dts/mt7621_ubnt_unifi-6-lite.dts | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/target/linux/ramips/dts/mt7621_ubnt_unifi-6-lite.dts b/target/linux/ramips/dts/mt7621_ubnt_unifi-6-lite.dts
index 0e56d16a7f..afd54e816b 100644
--- a/target/linux/ramips/dts/mt7621_ubnt_unifi-6-lite.dts
+++ b/target/linux/ramips/dts/mt7621_ubnt_unifi-6-lite.dts
@@ -90,6 +90,21 @@
 
 	nvmem-cells = <&macaddr_eeprom_6>;
 	nvmem-cell-names = "mac-address";
+
+	/* This is a workaround.
+	 *
+	 * Ubiquiti uses a +2 offset in the first octet relative
+	 * to the 2.4 GHz WMAC. Other octets are identical.
+	 *
+	 * The vendor firmware increases the last octet by 2 for each
+	 * VAP.
+	 *
+	 * This is in conflict on how mac80211 addresses subsequent VAPs.
+	 * mac80211 increases the first octet by two for each VAP, leading
+	 * to conflicting MAC addresses for subsequent interfaces.
+	 */
+	mac-address-increment = <1>;
+
 	ieee80211-freq-limit = <5000000 6000000>;
 };