DFS is not enabled, majority of 5GHz channels are not accessible

[Tomas Hlavacek]

The driver keeps reporting all DFS-dependant channels as disabled despite the correct regdomain is set in CRDA:

root@mamut:/home/patty# iw reg get
global
country CZ: DFS-ETSI
 (2400 - 2483 @ 40), (N/A, 20), (N/A)
 (5150 - 5250 @ 80), (N/A, 23), (N/A), NO-OUTDOOR, AUTO-BW
 (5250 - 5350 @ 80), (N/A, 20), (0 ms), NO-OUTDOOR, DFS, AUTO-BW
 (5470 - 5725 @ 160), (N/A, 26), (0 ms), DFS
 (57000 - 66000 @ 2160), (N/A, 40), (N/A)

root@mamut:/home/patty# iw list
Wiphy phy0
 max # scan SSIDs: 9
 max scan IEs length: 2304 bytes
 max # sched scan SSIDs: 0
 max # match sets: 0
 max # scan plans: 1
 max scan plan interval: -1
 max scan plan iterations: 0
 Retry short limit: 7
 Retry long limit: 4
 Coverage class: 0 (up to 0m)
 Supported Ciphers:
  * WEP40 (00-0f-ac:1)
  * WEP104 (00-0f-ac:5)
  * TKIP (00-0f-ac:2)
  * CCMP-128 (00-0f-ac:4)
 Available Antennas: TX 0 RX 0
 Supported interface modes:
   * IBSS
   * managed
   * AP
 Band 1:
  Capabilities: 0x1962
   HT20/HT40
   Static SM Power Save
   RX HT20 SGI
   RX HT40 SGI
   RX STBC 1-stream
   Max AMSDU length: 7935 bytes
   DSSS/CCK HT40
  Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
  Minimum RX AMPDU time spacing: 16 usec (0x07)
  HT Max RX data rate: 150 Mbps
  HT TX/RX MCS rate indexes supported: 0-7
  Bitrates (non-HT):
   * 1.0 Mbps
   * 2.0 Mbps
   * 5.5 Mbps
   * 11.0 Mbps
   * 6.0 Mbps
   * 9.0 Mbps
   * 12.0 Mbps
   * 18.0 Mbps
   * 24.0 Mbps
   * 36.0 Mbps
   * 48.0 Mbps
   * 54.0 Mbps
  Frequencies:
   * 2412 MHz [1] (20.0 dBm)
   * 2417 MHz [2] (20.0 dBm)
   * 2422 MHz [3] (20.0 dBm)
   * 2427 MHz [4] (20.0 dBm)
   * 2432 MHz [5] (20.0 dBm)
   * 2437 MHz [6] (20.0 dBm)
   * 2442 MHz [7] (20.0 dBm)
   * 2447 MHz [8] (20.0 dBm)
   * 2452 MHz [9] (20.0 dBm)
   * 2457 MHz [10] (20.0 dBm)
   * 2462 MHz [11] (20.0 dBm)
   * 2467 MHz [12] (20.0 dBm)
   * 2472 MHz [13] (20.0 dBm)
   * 2484 MHz [14] (disabled)
 Band 2:
  Capabilities: 0x1862
   HT20/HT40
   Static SM Power Save
   RX HT20 SGI
   RX HT40 SGI
   No RX STBC
   Max AMSDU length: 7935 bytes
   DSSS/CCK HT40
  Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
  Minimum RX AMPDU time spacing: 16 usec (0x07)
  HT Max RX data rate: 150 Mbps
  HT TX/RX MCS rate indexes supported: 0-7
  VHT Capabilities (0x03c00120):
   Max MPDU length: 3895
   Supported Channel Width: neither 160 nor 80+80
   short GI (80 MHz)
   +HTC-VHT
  VHT RX MCS set:
   1 streams: MCS 0-9
   2 streams: not supported
   3 streams: not supported
   4 streams: not supported
   5 streams: not supported
   6 streams: not supported
   7 streams: not supported
   8 streams: not supported
  VHT RX highest supported: 434 Mbps
  VHT TX MCS set:
   1 streams: MCS 0-9
   2 streams: not supported
   3 streams: not supported
   4 streams: not supported
   5 streams: not supported
   6 streams: not supported
   7 streams: not supported
   8 streams: not supported
  VHT TX highest supported: 434 Mbps
  Bitrates (non-HT):
   * 6.0 Mbps
   * 9.0 Mbps
   * 12.0 Mbps
   * 18.0 Mbps
   * 24.0 Mbps
   * 36.0 Mbps
   * 48.0 Mbps
   * 54.0 Mbps
  Frequencies:
   * 5180 MHz [36] (23.0 dBm)
   * 5200 MHz [40] (23.0 dBm)
   * 5220 MHz [44] (23.0 dBm)
   * 5240 MHz [48] (23.0 dBm)
   * 5260 MHz [52] (disabled)
   * 5280 MHz [56] (disabled)
   * 5300 MHz [60] (disabled)
   * 5320 MHz [64] (disabled)
   * 5500 MHz [100] (disabled)
   * 5520 MHz [104] (disabled)
   * 5540 MHz [108] (disabled)
   * 5560 MHz [112] (disabled)
   * 5580 MHz [116] (disabled)
   * 5600 MHz [120] (disabled)
   * 5620 MHz [124] (disabled)
   * 5640 MHz [128] (disabled)
   * 5660 MHz [132] (disabled)
   * 5680 MHz [136] (disabled)
   * 5700 MHz [140] (disabled)
   * 5720 MHz [144] (disabled)
   * 5745 MHz [149] (30.0 dBm)
   * 5765 MHz [153] (30.0 dBm)
   * 5785 MHz [157] (30.0 dBm)
   * 5805 MHz [161] (30.0 dBm)
   * 5825 MHz [165] (30.0 dBm)
   * 5845 MHz [169] (disabled)
   * 5865 MHz [173] (disabled)
   * 5885 MHz [177] (disabled)
 Supported commands:
   * new_interface
   * set_interface
   * new_key
   * start_ap
   * new_station
   * set_bss
   * join_ibss
   * set_pmksa
   * del_pmksa
   * flush_pmksa
   * remain_on_channel
   * frame
   * set_channel
   * connect
   * disconnect
 Supported TX frame types:
   * IBSS: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
   * managed: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
   * AP: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
   * AP/VLAN: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
   * P2P-client: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
   * P2P-GO: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0
 Supported RX frame types:
   * IBSS: 0xd0
   * managed: 0x40 0xd0
   * AP: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0
   * AP/VLAN: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0
   * P2P-client: 0x40 0xd0
   * P2P-GO: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0
 WoWLAN support:
   * wake up on anything (device continues operating normally)
 software interface modes (can always be added):
 interface combinations are not supported
 Device supports scan flush.
 Supported extended features:

I have focal using current kernel and driver package:

root@mamut:/home/patty# uname -a
Linux mamut 5.4.0-14-generic #17-Ubuntu SMP Thu Feb 6 22:47:59 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
root@mamut:/home/patty# dpkg -l | grep rtl8821
ii rtl8821ce-dkms 5.5.2.1-0ubuntu3 all DKMS source for the Realtek 8821C PCIe WiFi driver

It seems to be a known problem: https://github.com/Syniurge/rtl8821ce/commit/5c0667729d9b7257894ef92dbfe685dc23661a5e