[PATCH wireless 2/2] wifi: rtw88: restore the control frame filter when the device is started

[Jeremy Fareau <jeremy.fareau@gmail.com>]

Commit ed51a86b787f ("wifi: rtw88: Enable receiving control frames in
monitor mode") writes REG_RXFLTMAP1 from configure_filter(), but that
register is reset to the chip default by the chip's mac_init() during
power_on().  mac80211 only calls ieee80211_ops::configure_filter() when
its own filter flags change, so after a stop/start cycle the flags are
unchanged and the control frame filter silently reverts: monitor mode
stops delivering control frames again.

Keep track of the value configure_filter() last asked for and restore
it in rtw_core_start(), next to the RCR restore, which exists for the
same reason.

Measured on an RTL8814AU and an RTL8812AU in monitor mode on channel 6,
40 s captures taken after a down/up cycle.  Control frames go from 0 to
23184 and from 0 to 483 respectively; without this change both are 0.

Fixes: ed51a86b787f ("wifi: rtw88: Enable receiving control frames in monitor mode")
Assisted-by: LLM
Signed-off-by: Jeremy Fareau <jeremy.fareau@gmail.com>
---
 drivers/net/wireless/realtek/rtw88/mac80211.c | 5 +++--
 drivers/net/wireless/realtek/rtw88/main.c     | 8 ++++++++
 drivers/net/wireless/realtek/rtw88/main.h     | 1 +
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw88/mac80211.c b/drivers/net/wireless/realtek/rtw88/mac80211.c
index 827f38390969..84d869f1efe0 100644
--- a/drivers/net/wireless/realtek/rtw88/mac80211.c
+++ b/drivers/net/wireless/realtek/rtw88/mac80211.c
@@ -300,9 +300,10 @@ static void rtw_ops_configure_filter(struct ieee80211_hw *hw,
 
 	if (changed_flags & FIF_CONTROL) {
 		if (*new_flags & FIF_CONTROL)
-			rtw_write16(rtwdev, REG_RXFLTMAP1, 0xffff);
+			rtwdev->hal.rxfltmap1_cur = 0xffff;
 		else
-			rtw_write16(rtwdev, REG_RXFLTMAP1, rtwdev->hal.rxfltmap1);
+			rtwdev->hal.rxfltmap1_cur = rtwdev->hal.rxfltmap1;
+		rtw_write16(rtwdev, REG_RXFLTMAP1, rtwdev->hal.rxfltmap1_cur);
 	}
 	if (changed_flags & FIF_ALLMULTI) {
 		if (*new_flags & FIF_ALLMULTI)
diff --git a/drivers/net/wireless/realtek/rtw88/main.c b/drivers/net/wireless/realtek/rtw88/main.c
index cd9254370fcc..ea61020a0622 100644
--- a/drivers/net/wireless/realtek/rtw88/main.c
+++ b/drivers/net/wireless/realtek/rtw88/main.c
@@ -1528,6 +1528,14 @@ int rtw_core_start(struct rtw_dev *rtwdev)
 	/* rcr reset after powered on */
 	rtw_write32(rtwdev, REG_RCR, rtwdev->hal.rcr);
 
+	/* REG_RXFLTMAP1 is reset by the chip's mac_init() during power_on(),
+	 * and mac80211 only calls ieee80211_ops::configure_filter() when its
+	 * own filter flags change.  After a stop/start cycle the flags are
+	 * unchanged, so restore the value configure_filter() last asked for.
+	 */
+	if (rtwdev->hal.rxfltmap1_cur)
+		rtw_write16(rtwdev, REG_RXFLTMAP1, rtwdev->hal.rxfltmap1_cur);
+
 	ieee80211_queue_delayed_work(rtwdev->hw, &rtwdev->watch_dog_work,
 				     RTW_WATCH_DOG_DELAY_TIME);
 
diff --git a/drivers/net/wireless/realtek/rtw88/main.h b/drivers/net/wireless/realtek/rtw88/main.h
index c6e981ba7986..5a9bcc4fdff9 100644
--- a/drivers/net/wireless/realtek/rtw88/main.h
+++ b/drivers/net/wireless/realtek/rtw88/main.h
@@ -1964,6 +1964,7 @@ struct rtw_sar {
 struct rtw_hal {
 	u32 rcr;
 	u16 rxfltmap1;
+	u16 rxfltmap1_cur;
 
 	u32 chip_version;
 	u8 cut_version;
-- 
2.43.0