Workaround:
Download the firmware rt2800.bin file and copy it to the/lib/firmware
If you finish the above steps, run ifconfig wlan0 up still prompts
phy0 -> rt2x00lib_request_firmware: Error - Failed to request Firmware.ifconfig: SIOCSIFFLAGS: No such file or directory
Look down, then, that's how I solved the problem.
Typically, the NIC receives a request from the kernel to load rt2800.bin This firmware message, from the/lib/firmware directory to find Rt2800.bin, if you can find the words loaded successfully.
The network card with the value set in the/proc/sys/kernel/hotplug to achieve the load function, on the ARM board this value is/sbib/mdev, if the above problem, it is possible that this value is set incorrectly, the following command can be set:
echo /sbin/mdev > /proc/sys/kernel/hotplug
Run Ifconfig wlan0 up again, perfect solution!
rt3070 Wireless card Cannot find firmware problem under Linux