"STA-OPMODE-SMPS-MODE-CHANGED" what that mean?

"wlan1: STA-OPMODE-SMPS-MODE-CHANGED xxxxxx static"
If that client(xxxxxx) is a xiaomi phone, Goto phone's wifi: "Connection Type", change "High speed" to "Compatibility", solved!
Guess it is a compatibility problem between router and client.
Only reboot the router did not help.