After read the mt76 source code, I find the source code miss eerpom 0x34 setting (not a real eeprom, just flash factory partition), and 0x34 is used to choose antenna number…

So fix is pretty simple:

--- a/mt7603/init.c
+++ b/mt7603/init.c
@@ -277,6 +277,9 @@ mt7603_init_hardware(struct mt7603_dev *dev)
        if (ret < 0)
                return ret;
 
+       if (((u8*)dev->mphy.eeprom.data)[MT_EE_NIC_CONF_0] == 0x11)
+               dev->mphy.antenna_mask = 1;
+
        ret = mt7603_dma_init(dev);
        if (ret)
                return ret;

Once we find 0x34(MT_EE_NIC_CONF_0) is 0x11, force the driver use one antenna. That’s all.

Now after over 1 hour test, this mt76 driver is working very well and stably at >= 52Mbps 1T1R.

Develop on a chip like MT7628 is full of adventure…For new version of firmware I plan to use opensource MT76 driver instead of MT7628 driver. Weird thing is MT76 works well on some devices, but not well on some others, include VoCore2.

I guess it is antenna issue, because for normal WIFI4 routers default has two antennas works at same time for 300Mbps, 802.11n mode; but for VoCore2, default antenna 2 is disabled to save power and avoid cross talk when no second antenna attached.

Thanks to github MT76 contributors, I have some clues to fix this: https://github.com/openwrt/mt76/issues/423

After apply that patch, change mt76-2020-03-10-08054d5a/mt7603/init.c line 538

- dev->mt76.antenna_mask = 1;
+ dev->mt76.antenna_mask = 3;

I get a good result, 5minute no disconnect anymore.

...
[  5] 297.00-298.00 sec  6.31 MBytes  52.9 Mbits/sec                  
[  5] 298.00-299.00 sec  6.38 MBytes  53.5 Mbits/sec                  
[  5] 299.00-300.00 sec  6.41 MBytes  53.7 Mbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-300.00 sec  1.75 GBytes  50.2 Mbits/sec                  sender
[  5]   0.00-300.07 sec  1.75 GBytes  50.2 Mbits/sec                  receiver

So this should be the solution, just need test more. Currently we store 1T1R and 2T2R parameter to factory setting partition in flash, so there are two ways, one is to add factory setting patch to change it, another is to add DTS setting patch to change it, emm, which way is better? hard choice.

To be continue…