[PATCH rtw-next v10 3/3] wifi: rtw88: time the countdown downloads from the TBTT

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

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

The countdown downloads are queued one beacon interval apart, with no
relation to the TBTT. A download that runs late past the next TBTT
leaves a count out of the air.

Queue each download 10 ms after the next TBTT, read from the TSF, so it
may run late by almost a beacon interval; a later one is followed by
the next at once. A TSF jump, an IBSS merge or a reset, restarts the
schedule from the next TBTT.

The first count is downloaded the same way, not when mac80211 changes
the beacon: a download close to a TBTT keeps beacons off the air. On an
RTL8821CU and an RTL8822CU a TBTT during the download sent no beacon or
the old one. On an RTL8822CE a TBTT up to about 100 us before the
download sent none and the next beacon stayed out too, and with a count
of 2 no CSA beacon went out. The switch completes up to one beacon
interval later. The replay after a hardware restart still downloads at
once.

The USB chips raise no TBTT interrupt, so the TSF register is read. The
beaconing interface is always on port 0: rtw_core_port_switch() moves
an AP there, an IBSS runs alone.

Signed-off-by: Mehmet Fide <mehmet.fide@screeningeagle.com>
---

Notes:
    Changes in v10:
    - the first count is downloaded by the countdown work, 10 ms after the
      next TBTT, and no longer when mac80211 changes the beacon. v9 took a
      TBTT up to 10 ms before the start as the one that sent the first
      count, but a TBTT during the download sends no CSA beacon, and with
      a count of 2 none went out at all (Luka). No download runs close to
      a TBTT now, so there is nothing left to guess
    - rebased on rtw-next
    - Acked-by from Ping-Ke and Reviewed-by from Luka dropped for the
      changed code
    
    Changes in v9:
    - Acked-by from Ping-Ke (on v8) and Reviewed-by from Luka
    
    Changes in v8:
    - the TSF read retries once, if the high word changed, instead of
      looping (Ping-Ke)
    - rtw_fw_csa_queue() takes a start argument and reads the TSF once,
      also on start (Ping-Ke)
    - the port 0 comment is gone, the commit message says it (Ping-Ke)
    - empty lines where asked (Ping-Ke)
    
    Changes in v7:
    - new patch, from Ping-Ke's review of the countdown pacing in v6

 drivers/net/wireless/realtek/rtw88/fw.c       | 48 ++++++++++++++++---
 drivers/net/wireless/realtek/rtw88/mac80211.c |  7 ++-
 drivers/net/wireless/realtek/rtw88/main.h     |  2 +-
 drivers/net/wireless/realtek/rtw88/reg.h      |  1 +
 4 files changed, 48 insertions(+), 10 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw88/fw.c b/drivers/net/wireless/realtek/rtw88/fw.c
index 2d81aaeed0d7..c30aa938f9a9 100644
--- a/drivers/net/wireless/realtek/rtw88/fw.c
+++ b/drivers/net/wireless/realtek/rtw88/fw.c
@@ -3,6 +3,7 @@
  */
 
 #include <linux/iopoll.h>
+#include <linux/math64.h>
 
 #include "main.h"
 #include "coex.h"
@@ -1809,14 +1810,47 @@ bool rtw_fw_csa_active(struct rtw_dev *rtwdev)
 	return !!rtwdev->csa_vif;
 }
 
-/* paced from the first download: a late one does not delay the next */
-static void rtw_fw_csa_queue(struct rtw_dev *rtwdev, struct ieee80211_vif *vif)
+#define RTW_CSA_TBTT_MARGIN_US	10000
+
+static u64 rtw_fw_read_tsf(struct rtw_dev *rtwdev)
+{
+	u32 hi, lo, tmp;
+
+	hi = rtw_read32(rtwdev, REG_TSFTR + 4);
+	lo = rtw_read32(rtwdev, REG_TSFTR);
+	tmp = rtw_read32(rtwdev, REG_TSFTR + 4);
+	if (tmp != hi) {
+		hi = tmp;
+		lo = rtw_read32(rtwdev, REG_TSFTR);
+	}
+
+	return ((u64)hi << 32) | lo;
+}
+
+static void rtw_fw_csa_queue(struct rtw_dev *rtwdev, struct ieee80211_vif *vif,
+			     bool start)
 {
 	u32 interval = ieee80211_tu_to_usec(vif->bss_conf.beacon_int);
+	u64 tsf = rtw_fw_read_tsf(rtwdev);
 	s64 delay;
+	u32 rem;
+
+	if (start) {
+		div_u64_rem(tsf, interval, &rem);
+		rtwdev->csa_tbtt = tsf - rem + interval;
+	} else {
+		rtwdev->csa_tbtt += interval;
+	}
+
+	delay = rtwdev->csa_tbtt + RTW_CSA_TBTT_MARGIN_US - tsf;
+	if (delay > interval + RTW_CSA_TBTT_MARGIN_US ||
+	    delay < -(s64)interval) {
+		/* the TSF jumped: restart from the next TBTT */
+		div_u64_rem(tsf, interval, &rem);
+		rtwdev->csa_tbtt = tsf - rem + interval;
+		delay = rtwdev->csa_tbtt + RTW_CSA_TBTT_MARGIN_US - tsf;
+	}
 
-	rtwdev->csa_due = ktime_add_us(rtwdev->csa_due, interval);
-	delay = ktime_us_delta(rtwdev->csa_due, ktime_get());
 	ieee80211_queue_delayed_work(rtwdev->hw, &rtwdev->csa_beacon_work,
 				     usecs_to_jiffies(max(delay, 0)));
 }
@@ -1829,8 +1863,8 @@ void rtw_fw_csa_start(struct rtw_dev *rtwdev, struct ieee80211_vif *vif)
 		return;
 
 	rtwdev->csa_vif = vif;
-	rtwdev->csa_due = ktime_get();
-	rtw_fw_csa_queue(rtwdev, vif);
+
+	rtw_fw_csa_queue(rtwdev, vif, true);
 }
 
 void rtw_fw_csa_stop(struct rtw_dev *rtwdev, struct ieee80211_vif *vif)
@@ -1880,7 +1914,7 @@ void rtw_fw_csa_beacon_work(struct work_struct *work)
 	if (!ieee80211_beacon_cntdwn_is_complete(vif, 0)) {
 		rtw_fw_download_rsvd_page(rtwdev);
 		rtw_send_rsvd_page_h2c(rtwdev);
-		rtw_fw_csa_queue(rtwdev, vif);
+		rtw_fw_csa_queue(rtwdev, vif, false);
 	} else {
 		ieee80211_csa_finish(vif, 0);
 	}
diff --git a/drivers/net/wireless/realtek/rtw88/mac80211.c b/drivers/net/wireless/realtek/rtw88/mac80211.c
index e6c9866fd599..dbd148760b9b 100644
--- a/drivers/net/wireless/realtek/rtw88/mac80211.c
+++ b/drivers/net/wireless/realtek/rtw88/mac80211.c
@@ -441,8 +441,11 @@ static void rtw_ops_bss_info_changed(struct ieee80211_hw *hw,
 
 	if (changed & BSS_CHANGED_BEACON) {
 		rtw_set_dtim_period(rtwdev, conf->dtim_period);
-		rtw_fw_download_rsvd_page(rtwdev);
-		rtw_send_rsvd_page_h2c(rtwdev);
+		/* the countdown downloads its beacons after a TBTT */
+		if (!conf->csa_active || changed & BSS_CHANGED_BEACON_ENABLED) {
+			rtw_fw_download_rsvd_page(rtwdev);
+			rtw_send_rsvd_page_h2c(rtwdev);
+		}
 		/* restart replay resumes it, a beacon without CSA ends it */
 		if (conf->csa_active)
 			rtw_fw_csa_start(rtwdev, vif);
diff --git a/drivers/net/wireless/realtek/rtw88/main.h b/drivers/net/wireless/realtek/rtw88/main.h
index 5d18841a705f..466992b85c43 100644
--- a/drivers/net/wireless/realtek/rtw88/main.h
+++ b/drivers/net/wireless/realtek/rtw88/main.h
@@ -2096,7 +2096,7 @@ struct rtw_dev {
 	struct work_struct update_beacon_work;
 	struct delayed_work csa_beacon_work;
 	struct ieee80211_vif *csa_vif;
-	ktime_t csa_due;
+	u64 csa_tbtt;
 
 	/* used to protect txqs list */
 	spinlock_t txq_lock;
diff --git a/drivers/net/wireless/realtek/rtw88/reg.h b/drivers/net/wireless/realtek/rtw88/reg.h
index afcdb66fdb9a..3ff4ae0885ef 100644
--- a/drivers/net/wireless/realtek/rtw88/reg.h
+++ b/drivers/net/wireless/realtek/rtw88/reg.h
@@ -506,6 +506,7 @@
 #define REG_USTIME_TSF		0x055C
 #define REG_BCN_MAX_ERR		0x055D
 #define REG_RXTSF_OFFSET_CCK	0x055E
+#define REG_TSFTR		0x0560
 #define REG_MISC_CTRL		0x0577
 #define BIT_EN_FREE_CNT		BIT(3)
 #define BIT_DIS_SECOND_CCA	(BIT(0) | BIT(1))
-- 
2.56.0