Access point on brcmfmac driver

I have banana pi m2+ with ampak AP6212.

Install Armbian 5.75 with Linux kernel 4.19.20

Driver on wi-fi brcmfmac. Wi-Fi access point actived via armbian-config.

ifconfig:

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.20  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 fe80::81:fcff:fe71:785b  prefixlen 64  scopeid 0x20<link>
        ether 02:81:fc:71:78:5b  txqueuelen 1000  (Ethernet)
        RX packets 76186  bytes 46503714 (46.5 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12755  bytes 2691167 (2.6 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 38  

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 1954  bytes 587743 (587.7 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1954  bytes 587743 (587.7 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.24.1.1  netmask 255.255.255.0  broadcast 172.24.1.255
        inet6 fe80::12d0:7aff:fe79:194f  prefixlen 64  scopeid 0x20<link>
        ether 10:d0:7a:79:19:4f  txqueuelen 1000  (Ethernet)
        RX packets 12676  bytes 2511391 (2.5 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 37290  bytes 44389268 (44.3 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

iwconfig wlan0:

wlan0     IEEE 802.11  Mode:Master  Tx-Power=31 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
 

Working good, but on smartphone disabled Internet working after 2-5 minutes(sometime 20-30 minites). Wi-fi Connection working on smartphone andnot disconnected, but Internet was gone and ping failed smartphone. From BPI arping working...ping failed.

Try set skip_inactivity_poll=1 in hostapd.conf - still Internet disconnecting.

What's problem...maybe in driver brcmfmac not stable?!