device randomly loses wifi functionality (no SSID broadcast) after flashing

[vinczo]

Hi,

I have developed a custom firmware for RT5350F-OLinuXino.

I flash this firmware using U-Boot's second option:

2: Load system code then write to Flash via TFTP.

From time to time, the flashed devices loses wifi functionality. I mean it is not able to broadcast wifi SSID anymore. iw dev shows the wifi device as up and broadcasting the SSID but no SSID appears on my phone or any other device when scanning available devices.

root@TEST-5f27:~# iw dev
phy#0
   Interface wlan0
      ifindex 10
      wdev 0x2
      addr 80:1f:12:7e:5f:27
      ssid TEST-AP-5f27
      type AP
      channel 11 (2462 MHz), width: 20 MHz, center1: 2462 MHz
      txpower 20.00 dBm

The problem is not solved by rebooting, modifying /etc/config/wireless, restarting the wifi or networking service.

The only way I have found to solve the issue is to :

• take a working device (flashed with the same firmware)
• read its ROM (ROM~8M while firmware flashed~4M)
• write this ROM image to the not working device
• boot and wifi works again ! Note, if you flash the firmware again you might end up with a working/not working device... again...

I have been flashing these kind of devices for several years now and it's only since OpenWrt-18.06 that I seem to encounter this issue.

Do you know where does this come from? Is there a fix?

Thanks for you help.