Flashing OpenWrt-18.06 to device loses wifi functionality (no SSID broadcast) even after reboot


I have developed a custom firmware for RT5350F-OLinuXino from Olimex.

I flash this firmware using U-Boot's second option with an TFTP server :

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.

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.

  • What channel is it set to?
  • Did you keep settings during the sysupgrade?
  • Does this issue occur with a pre-built image from downloads.openwrt.org ?
  • channel is set to 11
  • keeping settings using u-boot menu to flash (I'm not using the sysupgrade command) ? can you do that ?
  • I don't know since I'm using my own custom firmware and it happens randomly so I can't reproduce it easily...

doesn't openwrt disables wifi at first boot? IIRC I had to enable it on luci.

Yes but I have it enabled in my custom firmware.
While connected through UART for debugging, it appears as up and broadcasting.

root@TEST-5f27:~# iw dev
	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 issue comes from the factory partition. I suspect that the products I received had the factory partition corrupted...

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