[PATCH rtw-next v2 3/3] wifi: rtw88: widen the ATIM window while an AP interface is up

[Mehmet Fide <mehmet.fide@gmail.com>]

From: Mehmet Fide <mehmet.fide@screeningeagle.com>

The frames held for dozing stations go out right after the DTIM beacon
and only for the duration of the ATIM window. The chips come up with a
2 TU window (the two that program it set 0x2 at init), which drains
about three frames per DTIM; the vendor driver sets 0xa or 0xc in AP
mode instead. With the 2 TU window the measured page pool exhaustion
takes ~100 s of ordinary multicast chatter; at 0x4 the same storm
already drains, so 0xa leaves comfortable headroom.

Program 0xa when an AP interface starts and put the default back when
it stops, since most chips never initialize the register themselves.
The bound and the filter of the previous patches still apply: the
window adds drain capacity, the budget protects the pool when that is
not enough, the filter keeps chatter off the beacon-paced path.

Suggested-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Mehmet Fide <mehmet.fide@screeningeagle.com>
---
v2:
- new patch, REG_ATIMWND 0xa in AP mode as in the vendor driver, back to
  the 0x2 default on stop_ap since most chips never program it (Ping-Ke)

 drivers/net/wireless/realtek/rtw88/mac80211.c | 2 ++
 drivers/net/wireless/realtek/rtw88/reg.h      | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw88/mac80211.c b/drivers/net/wireless/realtek/rtw88/mac80211.c
index 0b622d7663b6..2a9b09fa76e7 100644
--- a/drivers/net/wireless/realtek/rtw88/mac80211.c
+++ b/drivers/net/wireless/realtek/rtw88/mac80211.c
@@ -474,6 +474,7 @@ static int rtw_ops_start_ap(struct ieee80211_hw *hw,
 
 	mutex_lock(&rtwdev->mutex);
 	rtw_write32_set(rtwdev, REG_TCR, BIT_TCR_UPDATE_HGQMD);
+	rtw_write16(rtwdev, REG_ATIMWND, ATIMWND_AP);
 	rtwdev->ap_active = true;
 	rtw_store_op_chan(rtwdev, true);
 	chip->ops->phy_calibration(rtwdev);
@@ -490,6 +491,7 @@ static void rtw_ops_stop_ap(struct ieee80211_hw *hw,
 
 	mutex_lock(&rtwdev->mutex);
 	rtw_write32_clr(rtwdev, REG_TCR, BIT_TCR_UPDATE_HGQMD);
+	rtw_write16(rtwdev, REG_ATIMWND, ATIMWND_DEFAULT);
 	rtwdev->ap_active = false;
 	if (!rtw_core_check_sta_active(rtwdev))
 		rtw_clear_op_chan(rtwdev);
diff --git a/drivers/net/wireless/realtek/rtw88/reg.h b/drivers/net/wireless/realtek/rtw88/reg.h
index 08e9494977e0..0b9ba6f37680 100644
--- a/drivers/net/wireless/realtek/rtw88/reg.h
+++ b/drivers/net/wireless/realtek/rtw88/reg.h
@@ -483,6 +483,8 @@
 #define REG_DRVERLYINT		0x0558
 #define REG_BCNDMATIM		0x0559
 #define REG_ATIMWND		0x055A
+#define ATIMWND_DEFAULT		0x2
+#define ATIMWND_AP		0xa
 #define REG_USTIME_TSF		0x055C
 #define REG_BCN_MAX_ERR		0x055D
 #define REG_RXTSF_OFFSET_CCK	0x055E
-- 
2.55.0