Re: rtw89: BT connect state differs between scoreboard and bt_info on RTL8851B

[Maxim Skokov]

> We found the problem recently, and ongoing to send out the patch.
> Please try the attachment.

Applied on 7.3.0-rc1, rebuilt the rtw89 modules only. RTL8851BE,
WL_FW 0.29.41.5.

The hardware read works. With RTW89_DBG_BTC on, during a radio state
change:

  [BTC], read scbd bt0: 0x40000013
  [BTC], read scbd bt0: 0xc0000013

BTC_BSCB_BT_CONNECT, BIT(16), is not set in either value, so the register
holds what the C2H path was already reporting.

status.map.connect still alternates. 90 samples of btc_info, one per
second, with the mechanism reason and the WL link mode beside it:

  16  connect:Y  reason:UPDATE_BT_INFO   link_mode:STA
   1  connect:Y  reason:NTFY_SWBAND      link_mode:STA
  70  connect:N  reason:NTFY_POWEROFF    link_mode:STA
   2  connect:N  reason:UPDATE_BT_SCBD   link_mode:STA
   1  connect:N  reason:NTFY_SCAN_START  link_mode:STA

The same sampling on the unpatched module, 30 samples two seconds apart,
gave 28 N and 2 Y, so this part is unchanged.

The mailbox reports the device as connected throughout:
raw_data[49 01 c9 00 04 00], so raw_info[2] = 0x49 and lb2.connect = 1,
with A2DP_active:Y. The sink was connected and playing for all of the
above, and WL stayed in STA mode, retrying association without completing
it.

Is BTC_BSCB_BT_CONNECT expected to be set by BT firmware on this chip? If
not, status.map.connect will keep being overwritten from the scoreboard
after _update_bt_info() has written it from the mailbox.