CSA to DFS channel and ACS not compatible?

[gluedig]

Hi,

I have 5GHz AP configured with (among other):
ieee80211h=1
acs_exclude_dfs=1
channel=acs_survey

So ACS chooses non-DFS channel on startup (most commonly 36 or 40).

Now, I'm trying to switch channel to ex. 52 which is DFS (and not 
cleared yet) in my regulatory domain (PL) by doing:
hostapd_cli chan_switch 10 5260 bandwidth=20

And that results in AP interface going down and up with following prints:
Tue Oct  8 17:04:49 2024 daemon.debug hostapd: DFS CAC required: (5250, 
5270): in range: yes
Tue Oct  8 17:04:49 2024 daemon.debug hostapd: DFS/CAC to (channel=52, 
freq=5260, sec_channel_offset=0, bw=20, center_freq1=0)
Tue Oct  8 17:04:49 2024 daemon.debug hostapd: Restarting all 
CSA-related BSSes
Tue Oct  8 17:04:49 2024 daemon.notice hostapd: ath0: AP-DISABLED
...
Tue Oct  8 17:04:50 2024 daemon.notice hostapd: ath0: interface state 
DISABLED->COUNTRY_UPDATE
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: Previous country code PL, 
new country code PL
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: nl80211: Regulatory 
information - country=PL (DFS-ETSI)
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: nl80211: 2402-2482 @ 40 
MHz 20 mBm
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: nl80211: 5170-5250 @ 80 
MHz 23 mBm (no outdoor)
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: nl80211: 5250-5330 @ 80 
MHz 23 mBm (no outdoor) (DFS)
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: nl80211: 5490-5590 @ 80 
MHz 30 mBm (DFS)
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: nl80211: 5590-5650 @ 40 
MHz 30 mBm (DFS)
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: nl80211: 5650-5710 @ 40 
MHz 30 mBm (DFS)
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: nl80211: Mode IEEE 
802.11a: 5180 5200 5220 5240 5260[RADAR] 5280[RADAR] 5300[RADAR] 
5320[RADAR] 5500[RADAR] 5520[RADAR] 5540[RADAR] 5560[RADAR] 5580[RADAR] 
5600[RADAR] 5620[RADAR] 5640[RADAR] 5660[RADAR] 5680[RADAR] 5700[RADAR] 
5720[DISABLED][RADAR] 5745[DISABLED] 5765]
Tue Oct  8 17:04:50 2024 daemon.notice hostapd: ACS: Automatic channel 
selection started, this may take a bit
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: ACS: Scanning 1 / 5
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: ath0: nl80211: scan request
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: nl80211: Passive scan 
requested
Tue Oct  8 17:04:50 2024 daemon.debug hostapd: Scan requested (ret=0) - 
scan timeout 10 seconds
Tue Oct  8 17:04:50 2024 daemon.notice hostapd: ath0: interface state 
COUNTRY_UPDATE->ACS
Tue Oct  8 17:04:50 2024 daemon.notice hostapd: ath0: ACS-STARTED
...
Tue Oct  8 17:04:53 2024 daemon.debug hostapd: ACS: Survey analysis for 
selected bandwidth 20 MHz
Tue Oct  8 17:04:53 2024 daemon.debug hostapd: ACS:  * channel 36: total 
interference = 0.048
Tue Oct  8 17:04:53 2024 daemon.debug hostapd: ACS:  * channel 40: total 
interference = 0.0413333
Tue Oct  8 17:04:53 2024 daemon.debug hostapd: ACS:  * channel 44: total 
interference = 0.0666667
Tue Oct  8 17:04:53 2024 daemon.debug hostapd: ACS:  * channel 48: total 
interference = 0.0493333
Tue Oct  8 17:04:53 2024 daemon.debug hostapd: ACS: Ideal channel is 40 
(5200 MHz) with total interference factor of 0.0413333
Tue Oct  8 17:04:53 2024 daemon.notice hostapd: ath0: ACS-COMPLETED 
freq=5200 channel=40

After that it's back on same channel and according to logs CAC on 
channel 52 is not done at all.

Is what I'm trying to do supported?
Should manual channel switch to DFS channel when ACS is configured work ok?

For context - doing same thing when channel is set manually (even to 
non-DFS one) works ok - CAC is triggered and new channel is used after 
being cleared.

Best regards
Piotr