[PATCH v2 1/2] wifi: rtw89: fix RX filter configuration for monitor mode

[ph4ntom-rev]

In upstream rtw89, enabling monitor mode (IEEE80211_CONF_MONITOR)
configures basic B_AX_SNIFFER_MODE in R_AX_RX_FLTR_OPT. However, on
RTW89_CHIP_AX hardware (specifically RTL8852AE), Control frames (ACK,
RTS, CTS, BlockAck) and non-matching BSSID frames remain suppressed by
the hardware MAC Address CAM filters.

To ensure promiscuous capture of all 802.11 management, control, and
data frames:
1. Clear unicast, broadcast, and multicast CAM match drops and beacon
   BSSID checks in rx_fltr when IEEE80211_CONF_MONITOR is active.
2. Ensure power management frames are delivered by setting B_AX_A_PWR_MGNT.
3. Apply the adjusted filter across all active MAC indices (RTW89_MAC_0
   and RTW89_MAC_1 for DBCC) without clobbering rtwdev->hal.rx_fltr,
   allowing the default filter to be restored when leaving monitor mode.

Signed-off-by: ph4ntom-rev <owner@xxxxxxxxxxxxxx>
---
v1 -> v2:
 - Integrate RX filter adjustment directly into rtw89_ops_configure_filter()
   rather than maintaining a separate helper that overwrote hal.rx_fltr.
 - Configure both MAC 0 and MAC 1 (when DBCC is enabled) seamlessly.
 - Remove manual register writes to subtype filters and preserve standard
   filter restoration when exiting monitor mode.
 drivers/net/wireless/realtek/rtw89/mac80211.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw89/mac80211.c b/drivers/net/wireless/realtek/rtw89/mac80211.c
index 0672d13..33a6598 100644
--- a/drivers/net/wireless/realtek/rtw89/mac80211.c
+++ b/drivers/net/wireless/realtek/rtw89/mac80211.c
@@ -369,6 +369,15 @@ static void rtw89_ops_configure_filter(struct ieee80211_hw *hw,
 		rx_fltr &= ~B_AX_A_A1_MATCH;
 	}
 
+	if (hw->conf.flags & IEEE80211_CONF_MONITOR) {
+		rx_fltr &= ~(B_AX_A_UC_CAM_MATCH |
+			     B_AX_A_BC_CAM_MATCH |
+			     B_AX_A_MC_LIST_CAM_MATCH |
+			     B_AX_A_BCN_CHK_EN |
+			     B_AX_UID_FILTER_MASK);
+		rx_fltr |= B_AX_A_PWR_MGNT;
+	}
+
 	rtw89_mac_set_rx_fltr(rtwdev, RTW89_MAC_0, rx_fltr);
 	if (!rtwdev->dbcc_en)
 		return;
-- 
2.53.0