Cannot maintain an ap with brcmfmac

Group,

I do not really know what has changed, but I can no longer maintain an
ap runnning with brcmfmac on my Pis with the brcmfmac43455 chip. The
firmware is current (and ahead of what RPiOS ships):

[    3.472501] brcmfmac: F1 signature read @0x18000000=0x15264345
[    3.493274] brcmfmac: brcmf_fw_alloc_request: using
brcm/brcmfmac43455-sdio for chip BCM4345/6
[    3.494583] usbcore: registered new interface driver brcmfmac
[    3.900038] brcmfmac: brcmf_c_process_txcap_blob: no txcap_blob
available (err=-2)
[    3.901161] brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM4345/6
wl0: Oct 28 2024 23:27:00 version 7.45.286 (be70ab3 CY) FWID
01-95efe7fa

I get this with the default RPiOS verison of hostapd:
# hostapd -v
hostapd v2.10
User space daemon for IEEE 802.11 AP management,
IEEE 802.1X/WPA/WPA2/EAP/RADIUS Authenticator
Copyright (c) 2002-2022, Jouni Malinen <[email protected]> and contributors

And also with the one I built from source. The latest hostapd I could find.
The git repo it is built from is from here: https://w1.fi/hostapd/

# hostapd -v
hostapd v2.11-hostap_2_11+
User space daemon for IEEE 802.11 AP management,
IEEE 802.1X/WPA/WPA2/EAP/RADIUS Authenticator
Copyright (c) 2002-2024, Jouni Malinen <[email protected]> and contributors

My hostapd.conf is:
# cat /etc/hostapd/hostapd.conf
# interface and driver
interface=ap0
driver=nl80211

ht_capab=[HT40][SHORT-GI-20][DSSS_CCK-40]

# WIFI-Config
ssid=TestAP
channel=6
hw_mode=g
wmm_enabled=1
macaddr_acl=0
auth_algs=1
max_num_sta=10

# WIFI authorization
wpa=2
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP CCMP
rsn_pairwise=CCMP
wpa_psk_radius=0
wpa_passphrase=secret123

If there is something wrong in my setup, let me know.

when I start hostapd with dnsmasq, an interface comes up and I can
connect. As soon as it connects, it disconnects:
Apr 20 12:57:39 pi4 systemd-networkd[181]: ap0: Gained carrier
Apr 20 12:57:39 pi4 dnsmasq[169728]: started, version 2.90 cachesize 150
Apr 20 12:57:39 pi4 dnsmasq[169728]: compile time options: IPv6
GNU-getopt DBus no-UBus i18n IDN2 DHCP DHCPv6 no-Lua TFTP conntrack
ipset nftset auth cryptohash DNSSEC loop-detect inotify dumpfile
Apr 20 12:57:39 pi4 dnsmasq[169728]: warning: interface ap0 does not
currently exist
Apr 20 12:57:39 pi4 dnsmasq-dhcp[169728]: DHCP, IP range 192.168.5.2
-- 192.168.5.254, lease time 1d
Apr 20 12:57:39 pi4 dnsmasq[169728]: reading /run/systemd/resolve/resolv.conf
Apr 20 12:57:39 pi4 dnsmasq[169728]: using nameserver 192.168.2.253#53
Apr 20 12:57:39 pi4 dnsmasq[169728]: read /etc/hosts - 8 names
Apr 20 12:57:39 pi4 hostapd[169681]: ap0: interface state UNINITIALIZED->ENABLED
Apr 20 12:57:39 pi4 hostapd[169681]: ap0: AP-ENABLED
Apr 20 12:57:39 pi4 resolvconf[169735]: Dropped protocol specifier
'.dnsmasq' from 'lo.dnsmasq'. Using 'lo' (ifindex=1).
Apr 20 12:57:39 pi4 resolvconf[169735]: Failed to set DNS
configuration: Link lo is loopback device.
Apr 20 12:57:39 pi4 systemd[1]: Started dnsmasq.service - dnsmasq - A
lightweight DHCP and caching DNS server.
Apr 20 12:57:40 pi4 kernel: brcmfmac: brcmf_cfg80211_set_power_mgmt:
power save disabled
Apr 20 12:57:48 pi4 kernel: ieee80211 phy0: brcmf_escan_timeout: timer expired
Apr 20 12:57:48 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: associated
Apr 20 12:57:48 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: associated
Apr 20 12:57:48 pi4 hostapd[169681]: ap0: AP-STA-CONNECTED 50:84:92:a6:7a:7a
Apr 20 12:57:48 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a
RADIUS: starting accounting session 4336779F2221A786
Apr 20 12:57:48 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a WPA:
pairwise key handshake completed (RSN)
Apr 20 12:57:48 pi4 hostapd[169681]: ap0: EAPOL-4WAY-HS-COMPLETED
50:84:92:a6:7a:7a
Apr 20 12:57:48 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a
RADIUS: starting accounting session 4336779F2221A786
Apr 20 12:57:48 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a WPA:
pairwise key handshake completed (RSN)
Apr 20 12:57:48 pi4 dnsmasq-dhcp[169728]: DHCPDISCOVER(ap0) 50:84:92:a6:7a:7a
Apr 20 12:57:48 pi4 dnsmasq-dhcp[169728]: DHCPOFFER(ap0) 192.168.5.214
50:84:92:a6:7a:7a
Apr 20 12:57:48 pi4 dnsmasq-dhcp[169728]: DHCPREQUEST(ap0)
192.168.5.214 50:84:92:a6:7a:7a
Apr 20 12:57:48 pi4 dnsmasq-dhcp[169728]: DHCPACK(ap0) 192.168.5.214
50:84:92:a6:7a:7a
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: disassociated
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: AP-STA-DISCONNECTED 50:84:92:a6:7a:7a
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: disassociated
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: disassociated
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: disassociated
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: disassociated
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: disassociated
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: associated
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: associated
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: AP-STA-CONNECTED 50:84:92:a6:7a:7a
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a
RADIUS: starting accounting session 33CFF844DBBE630F
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a WPA:
pairwise key handshake completed (RSN)
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: EAPOL-4WAY-HS-COMPLETED
50:84:92:a6:7a:7a
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a
RADIUS: starting accounting session 33CFF844DBBE630F
Apr 20 12:57:52 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a WPA:
pairwise key handshake completed (RSN)
Apr 20 12:57:52 pi4 dnsmasq-dhcp[169728]: DHCPDISCOVER(ap0) 50:84:92:a6:7a:7a
Apr 20 12:57:52 pi4 dnsmasq-dhcp[169728]: DHCPOFFER(ap0) 192.168.5.214
50:84:92:a6:7a:7a
Apr 20 12:57:52 pi4 dnsmasq-dhcp[169728]: DHCPREQUEST(ap0)
192.168.5.214 50:84:92:a6:7a:7a
Apr 20 12:57:52 pi4 dnsmasq-dhcp[169728]: DHCPACK(ap0) 192.168.5.214
50:84:92:a6:7a:7a
Apr 20 12:57:57 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: disassociated
Apr 20 12:57:57 pi4 hostapd[169681]: ap0: AP-STA-DISCONNECTED 50:84:92:a6:7a:7a
Apr 20 12:57:57 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: disassociated
Apr 20 12:57:57 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: disassociated
Apr 20 12:57:57 pi4 hostapd[169681]: ap0: STA 50:84:92:a6:7a:7a IEEE
802.11: disassociated
Apr 20 12:58:11 pi4 hostapd[169681]: ap0: interface state ENABLED->DISABLED
Apr 20 12:58:11 pi4 systemd[1]: Stopping hostapd.service - Hostapd
IEEE 802.11 AP, IEEE 802.1X/WPA/WPA2/EAP/RADIUS Authenticator...
Apr 20 12:58:11 pi4 hostapd[169681]: ap0: AP-DISABLED
Apr 20 12:58:11 pi4 hostapd[169681]: ap0: CTRL-EVENT-TERMINATING
Apr 20 12:58:11 pi4 hostapd[169681]: nl80211: deinit ifname=ap0
disabled_11b_rates=0
Apr 20 12:58:11 pi4 systemd-networkd[181]: ap0: Lost carrier
Apr 20 12:58:11 pi4 systemd[1]: hostapd.service: Deactivated successfully.
Apr 20 12:58:11 pi4 systemd[1]: Stopped hostapd.service - Hostapd IEEE
802.11 AP, IEEE 802.1X/WPA/WPA2/EAP/RADIUS Authenticator.
Apr 20 12:58:12 pi4 systemd[1]: Stopping dnsmasq.service - dnsmasq - A
lightweight DHCP and caching DNS server...
Apr 20 12:58:12 pi4 resolvconf[170375]: Dropped protocol specifier
'.dnsmasq' from 'lo.dnsmasq'. Using 'lo' (ifindex=1).
Apr 20 12:58:12 pi4 resolvconf[170375]: Failed to revert interface
configuration: Link lo is loopback device.
Apr 20 12:58:12 pi4 dnsmasq[169728]: exiting on receipt of SIGTERM
Apr 20 12:58:12 pi4 systemd[1]: dnsmasq.service: Deactivated successfully.
Apr 20 12:58:12 pi4 systemd[1]: Stopped dnsmasq.service - dnsmasq - A
lightweight DHCP and caching DNS server.
Apr 20 12:58:12 pi4 systemd-networkd[181]: ap0: Link DOWN
Apr 20 12:58:12 pi4 kernel: ieee80211 phy0:
brcmf_cfg80211_get_channel: chanspec failed (-52)