bes2600: Patch E — skip ps_state_lock when PSM-known-disabled

Per the Opus structural critique (PR #8 §2.4) and Sonnet review item 5.
The per-RX-frame early-data path takes ps_state_lock to double-check
whether a link entry transitioned to BES2600_LINK_SOFT (AP-side
power-save state machine, soft-link transition).

When c7 has latched pm_unsupported = true (firmware does not honor
PSM, see feedback_bes2600_firmware_no_psm memory), the AP power-save
state machine is dead and link entries never transition to LINK_SOFT.
The per-frame spin_lock_bh + double-check is wasted work.

This patch gates the lock acquisition on !pm_unsupported.  When the
latch is on (the steady state on the production-shipped bes2600
firmware), early_data RX frames bypass the spin_lock_bh and go
directly to ieee80211_rx_irqsafe.

If a future firmware drop fixes PSM, c7 self-clears pm_unsupported on
the first real PM_INDICATION and the locked path resumes.

Scope is narrower than Sonnet originally framed: only the per-RX-frame
hot path (txrx.c:1945-1951 in cleanups+G+D) is touched.  Other
ps_state_lock sites in txrx.c (lines 657, 1256, 1420, 1528) are TX
submission / multicast-start / link-id paths, not per-frame RX, and
not on the Bug #5 hot path.  Leave those alone.

Build verified: srcversion B5922B4933590F33207EE97 on ohm sandbox.

bes2600/bes2600.h

@@ -353,15 +353,23 @@ struct bes2600_common {
 	* Keeping in common structure for the time being. Will be moved to VIFF
 	* after the mechanism is clear */
 	u8				ba_tid_mask;
-	int				ba_acc; /*TODO: Same as above */
+	/*
-	int				ba_cnt; /*TODO: Same as above */
+	 * Patch D: ba_lock removed.  Per-frame TX/RX hot-path bumped these
-	int				ba_cnt_rx; /*TODO: Same as above */
+	 * counters under spin_lock_bh; the lock did not protect any
-	int				ba_acc_rx; /*TODO: Same as above */
+	 * compound invariant that atomic ops can't satisfy.  Counters are
-	int				ba_hist; /*TODO: Same as above */
+	 * now atomic_t; ba_armed gates the once-per-window mod_timer
-	struct timer_list		ba_timer;/*TODO: Same as above */
+	 * arm via cmpxchg so concurrent TX/RX at a fresh window each
-	spinlock_t			ba_lock; /*TODO: Same as above */
+	 * try to claim the arm and exactly one succeeds.
-	bool				ba_ena; /*TODO: Same as above */
+	 */
-	struct work_struct              ba_work; /*TODO: Same as above */
+	atomic_t			ba_acc;
+	atomic_t			ba_cnt;
+	atomic_t			ba_cnt_rx;
+	atomic_t			ba_acc_rx;
+	atomic_t			ba_armed;
+	int				ba_hist;
+	struct timer_list		ba_timer;
+	atomic_t			ba_ena;
+	struct work_struct              ba_work;
 	bool				is_BT_Present;
 	bool				is_go_thru_go_neg;
 	u8				conf_listen_interval;

bes2600/debug.c

@@ -110,17 +110,20 @@ static int bes2600_status_show_common(struct seq_file *seq, void *v)
 	int ba_cnt, ba_acc, ba_cnt_rx, ba_acc_rx, ba_avg = 0, ba_avg_rx = 0;
 	bool ba_ena;
 
-	spin_lock_bh(&hw_priv->ba_lock);
+	/*
-	ba_cnt = hw_priv->debug->ba_cnt;
+	 * Patch D: ba_lock removed.  hw_priv->debug->ba_* are written only
-	ba_acc = hw_priv->debug->ba_acc;
+	 * by the timer callback (single writer); reading without a lock is
+	 * fine for stats.  ba_ena is atomic_t.
+	 */
+	ba_cnt    = hw_priv->debug->ba_cnt;
+	ba_acc    = hw_priv->debug->ba_acc;
 	ba_cnt_rx = hw_priv->debug->ba_cnt_rx;
 	ba_acc_rx = hw_priv->debug->ba_acc_rx;
-	ba_ena = hw_priv->ba_ena;
+	ba_ena    = !!atomic_read(&hw_priv->ba_ena);
 	if (ba_cnt)
 		ba_avg = ba_acc / ba_cnt;
 	if (ba_cnt_rx)
 		ba_avg_rx = ba_acc_rx / ba_cnt_rx;
-	spin_unlock_bh(&hw_priv->ba_lock);
 
 	seq_puts(seq,   "BES2600 Wireless LAN driver status\n");
 	seq_printf(seq, "Hardware:   %d.%d\n",

bes2600/main.c

@@ -496,7 +496,7 @@ static struct ieee80211_hw *bes2600_init_common(size_t hw_priv_data_len)
 	INIT_LIST_HEAD(&hw_priv->event_queue);
 	INIT_WORK(&hw_priv->event_handler, bes2600_event_handler);
 	INIT_WORK(&hw_priv->ba_work, bes2600_ba_work);
-	spin_lock_init(&hw_priv->ba_lock);
+	/* Patch D: ba_lock removed; ba_acc/ba_cnt/etc are atomic_t. */
 	timer_setup(&hw_priv->ba_timer, bes2600_ba_timer, 0);
 
 	if (unlikely(bes2600_queue_stats_init(&hw_priv->tx_queue_stats,

bes2600/sta.c

@@ -2342,14 +2342,19 @@ void bes2600_join_work(struct work_struct *work)
 		//WARN_ON(wsm_reset(hw_priv, &reset, priv->if_id));
 		WARN_ON(wsm_set_block_ack_policy(hw_priv,
 			0, hw_priv->ba_tid_mask, priv->if_id));
-		spin_lock_bh(&hw_priv->ba_lock);
+		/*
-		hw_priv->ba_ena = false;
+		 * Patch D: ba_lock removed.  Disconnect-reset clears the
-		hw_priv->ba_cnt = 0;
+		 * counters and the arm flag; producers racing here cannot
-		hw_priv->ba_acc = 0;
+		 * cause harm — at worst they re-arm the timer and bump
+		 * counters that will be cleared on the next timer tick.
+		 */
+		atomic_set(&hw_priv->ba_ena, 0);
+		atomic_set(&hw_priv->ba_cnt, 0);
+		atomic_set(&hw_priv->ba_acc, 0);
 		hw_priv->ba_hist = 0;
-		hw_priv->ba_cnt_rx = 0;
+		atomic_set(&hw_priv->ba_cnt_rx, 0);
-		hw_priv->ba_acc_rx = 0;
+		atomic_set(&hw_priv->ba_acc_rx, 0);
-		spin_unlock_bh(&hw_priv->ba_lock);
+		atomic_set(&hw_priv->ba_armed, 0);
 
 		mgmt_policy.protectedMgmtEnable = 0;
 		mgmt_policy.unprotectedMgmtFramesAllowed = 1;
@@ -2629,10 +2634,11 @@ void bes2600_ba_work(struct work_struct *work)
 		return;*/
 
 	bes_devel("BA work****\n");
-	spin_lock_bh(&hw_priv->ba_lock);
+	/*
-//	tx_ba_tid_mask = hw_priv->ba_ena ? hw_priv->ba_tid_mask : 0;
+	 * Patch D: ba_lock removed.  ba_tid_mask is u8 set once at init
+	 * (main.c); reading it without a lock is fine.
+	 */
 	tx_ba_tid_mask = hw_priv->ba_tid_mask;
-	spin_unlock_bh(&hw_priv->ba_lock);
 
 	wsm_lock_tx(hw_priv);
 
@@ -2645,37 +2651,49 @@ void bes2600_ba_work(struct work_struct *work)
 void bes2600_ba_timer(struct timer_list *t)
 {
 	bool ba_ena;
+	int cnt, acc, cnt_rx, acc_rx;
 	struct bes2600_common *hw_priv = from_timer(hw_priv, t, ba_timer);
 
-	spin_lock_bh(&hw_priv->ba_lock);
+	/*
-	bes2600_debug_ba(hw_priv, hw_priv->ba_cnt, hw_priv->ba_acc,
+	 * Patch D: ba_lock removed.  Snapshot atomic counters into locals
-			hw_priv->ba_cnt_rx, hw_priv->ba_acc_rx);
+	 * for the predicate evaluation; producers may race incrementing
+	 * after the snapshot but the resulting decision is approximate
+	 * which the policy already tolerates (next timer tick re-evaluates).
+	 */
+	cnt    = atomic_read(&hw_priv->ba_cnt);
+	acc    = atomic_read(&hw_priv->ba_acc);
+	cnt_rx = atomic_read(&hw_priv->ba_cnt_rx);
+	acc_rx = atomic_read(&hw_priv->ba_acc_rx);
+
+	bes2600_debug_ba(hw_priv, cnt, acc, cnt_rx, acc_rx);
 
 	if (atomic_read(&hw_priv->scan.in_progress)) {
-		hw_priv->ba_cnt = 0;
+		atomic_set(&hw_priv->ba_cnt, 0);
-		hw_priv->ba_acc = 0;
+		atomic_set(&hw_priv->ba_acc, 0);
-		hw_priv->ba_cnt_rx = 0;
+		atomic_set(&hw_priv->ba_cnt_rx, 0);
-		hw_priv->ba_acc_rx = 0;
+		atomic_set(&hw_priv->ba_acc_rx, 0);
-		goto skip_statistic_update;
+		atomic_set(&hw_priv->ba_armed, 0);
+		return;
 	}
 
-	if (hw_priv->ba_cnt >= BES2600_BLOCK_ACK_CNT &&
+	if (cnt >= BES2600_BLOCK_ACK_CNT &&
-		(hw_priv->ba_acc / hw_priv->ba_cnt >= BES2600_BLOCK_ACK_THLD ||
+		(acc / cnt >= BES2600_BLOCK_ACK_THLD ||
-		(hw_priv->ba_cnt_rx >= BES2600_BLOCK_ACK_CNT &&
+		(cnt_rx >= BES2600_BLOCK_ACK_CNT &&
-		hw_priv->ba_acc_rx / hw_priv->ba_cnt_rx >=
+		acc_rx / cnt_rx >=
 			BES2600_BLOCK_ACK_THLD)))
 		ba_ena = true;
 	else
 		ba_ena = false;
 
-	hw_priv->ba_cnt = 0;
+	atomic_set(&hw_priv->ba_cnt, 0);
-	hw_priv->ba_acc = 0;
+	atomic_set(&hw_priv->ba_acc, 0);
-	hw_priv->ba_cnt_rx = 0;
+	atomic_set(&hw_priv->ba_cnt_rx, 0);
-	hw_priv->ba_acc_rx = 0;
+	atomic_set(&hw_priv->ba_acc_rx, 0);
+	atomic_set(&hw_priv->ba_armed, 0);
 
-	if (ba_ena != hw_priv->ba_ena) {
+	if (ba_ena != !!atomic_read(&hw_priv->ba_ena)) {
 		if (ba_ena || ++hw_priv->ba_hist >= BES2600_BLOCK_ACK_HIST) {
-			hw_priv->ba_ena = ba_ena;
+			atomic_set(&hw_priv->ba_ena, ba_ena ? 1 : 0);
 			hw_priv->ba_hist = 0;
 #if 0
 			bes_devel("[STA] %s block ACK:\n",
@@ -2685,9 +2703,6 @@ void bes2600_ba_timer(struct timer_list *t)
 		}
 	} else if (hw_priv->ba_hist)
 		--hw_priv->ba_hist;
-
-skip_statistic_update:
-	spin_unlock_bh(&hw_priv->ba_lock);
 }
 
 int bes2600_vif_setup(struct bes2600_vif *priv)

bes2600/txrx.c

@@ -995,14 +995,18 @@ bes2600_tx_h_ba_stat(struct bes2600_vif *priv,
 	if (!ieee80211_is_data(t->hdr->frame_control))
 		return;
 
-	spin_lock_bh(&hw_priv->ba_lock);
+	/*
-	hw_priv->ba_acc += t->skb->len - t->hdrlen;
+	 * Patch D: lock-free hot-path BA accounting.  atomic_inc + atomic_add
-	if (!(hw_priv->ba_cnt_rx || hw_priv->ba_cnt)) {
+	 * each per-frame; the once-per-window timer-arm uses cmpxchg on
+	 * ba_armed so concurrent TX/RX can't both try to set the timer and
+	 * we don't need cross-counter coherency on the ba_cnt/ba_cnt_rx pair.
+	 */
+	atomic_add(t->skb->len - t->hdrlen, &hw_priv->ba_acc);
+	atomic_inc(&hw_priv->ba_cnt);
+	if (atomic_cmpxchg(&hw_priv->ba_armed, 0, 1) == 0) {
 		mod_timer(&hw_priv->ba_timer,
 			jiffies + BES2600_BLOCK_ACK_INTERVAL);
 	}
-	hw_priv->ba_cnt++;
-	spin_unlock_bh(&hw_priv->ba_lock);
 }
 
 static int
@@ -1629,14 +1633,13 @@ bes2600_rx_h_ba_stat(struct bes2600_vif *priv,
 	if (!priv->setbssparams_done)
 		return;
 
-	spin_lock_bh(&hw_priv->ba_lock);
+	/* Patch D: lock-free hot-path BA accounting; see TX side comment. */
-	hw_priv->ba_acc_rx += skb_len - hdrlen;
+	atomic_add(skb_len - hdrlen, &hw_priv->ba_acc_rx);
-	if (!(hw_priv->ba_cnt_rx || hw_priv->ba_cnt)) {
+	atomic_inc(&hw_priv->ba_cnt_rx);
+	if (atomic_cmpxchg(&hw_priv->ba_armed, 0, 1) == 0) {
 		mod_timer(&hw_priv->ba_timer,
 			jiffies + BES2600_BLOCK_ACK_INTERVAL);
 	}
-	hw_priv->ba_cnt_rx++;
-	spin_unlock_bh(&hw_priv->ba_lock);
 }
 
 void bes2600_rx_cb(struct bes2600_vif *priv,
@@ -1939,13 +1942,31 @@ void bes2600_rx_cb(struct bes2600_vif *priv,
 	if (unlikely(bes2600_itp_rxed(hw_priv, skb)))
 		consume_skb(skb);
 	else if (unlikely(early_data)) {
-		spin_lock_bh(&priv->ps_state_lock);
+		/*
-		/* Double-check status with lock held */
+		 * Patch E: when c7 has latched pm_unsupported (firmware
-		if (entry->status == BES2600_LINK_SOFT)
+		 * doesn't honour PSM, see feedback_bes2600_firmware_no_psm),
-			skb_queue_tail(&entry->rx_queue, skb);
+		 * AP-side power-save state machine is dead and link entries
-		else
+		 * never transition to BES2600_LINK_SOFT.  The double-check
+		 * branch under ps_state_lock is unreachable in that case,
+		 * so skip the per-frame lock acquisition entirely and
+		 * deliver to mac80211 directly.
+		 *
+		 * On firmware that does honour PSM (the latch self-clears
+		 * if a real PM_INDICATION ever arrives — see c7), this
+		 * predicate flips back to false and the original locked
+		 * path is taken.
+		 */
+		if (hw_priv->bes_power.pm_unsupported) {
 			ieee80211_rx_irqsafe(priv->hw, skb);
-		spin_unlock_bh(&priv->ps_state_lock);
+		} else {
+			spin_lock_bh(&priv->ps_state_lock);
+			/* Double-check status with lock held */
+			if (entry->status == BES2600_LINK_SOFT)
+				skb_queue_tail(&entry->rx_queue, skb);
+			else
+				ieee80211_rx_irqsafe(priv->hw, skb);
+			spin_unlock_bh(&priv->ps_state_lock);
+		}
 	} else {
 		ieee80211_rx_irqsafe(priv->hw, skb);
 	}