bes2600: self-detect when firmware does not honor PSM and skip the cycle

The c6 series fixed several host-side bookkeeping bugs around PSM
transitions, but didn't address the underlying contract: this chip's
firmware (BES2600 with the Bestechnic Dec 2023 build that ships on
PineTab2 and most danctnix images) silently drops every WSM_set_pm
request without emitting the corresponding PM_INDICATION. The driver's
own power_down_work delayed work calls bes2600_pwr_enter_lp_mode every
~10s; without firmware acknowledgment each call burns 5s on
wait_for_completion_timeout(pm_enter_cmpl, 5*HZ) and produces a
recurring three-line cascade in dmesg:

  bes2600_pwr_enter_lp_mode, wait pm ind timeout
  bes2600_sdio_active failed, subsys:0
  bes2600_pwr_device_exit_lp_mode, active mcu fail

Confirmed by tripwire instrumentation on PineTab2 (linux-pinetab2
6.19.10-danctnix1, ohm) running the c5+c6 stack: zero
wsm_set_pm_indication() invocations across an entire boot, while
bes2600_pwr_enter_lp_mode timed out repeatedly, and
bes2600_sdio_active() consistently saw BES_SLAVE_STATUS_REG_ID return
0x2f (every "ready" bit set except MCU_WAKEUP_READY (bit 4) - the
firmware reports "I'm awake, there's nothing to wake from").

This patch makes the driver self-heal:

  * struct bes2600_pwr_t gains pm_unsupported (bool) and
    pm_consecutive_timeouts (unsigned int). Both initialised to
    0/false.

  * bes2600_pwr_enter_lp_mode early-returns -EOPNOTSUPP when
    pm_unsupported is set. Skips the per-VIF set_pm round-trip and
    the wait_for_completion entirely.

  * On the cmpxchg-success branch of the timeout path, we increment
    pm_consecutive_timeouts. When it crosses
    BES2600_PM_UNSUPPORTED_THRESHOLD (3, ~15s of trying), we latch
    pm_unsupported = true and force chip_pm_state = ACTIVE so that
    bes2600_pwr_device_exit_lp_mode's c6.2 skip branch covers the
    wake side (no gpio_wake / sbus_active / WSM_set_operational_mode
    reissue past the first one).

  * bes2600_pwr_notify_ps_changed resets pm_consecutive_timeouts to 0
    on any incoming PM indication, and clears pm_unsupported if it
    was previously latched. So a firmware update that fixes PM_IND
    delivery automatically re-enables PSM transitions without a
    driver rebuild.

mac80211's PSM requests via bes2600_set_pm() still flow to the
firmware unchanged; they just don't have host-side timeouts so they
remain silent regardless of firmware acknowledgment. Power
consumption goes up if the firmware actually CAN do PSM (we'd be
keeping the chip awake unnecessarily), but on a chip where the
counter trips this trade-off is forced anyway: the chip stayed awake
under the broken cascade as well, just with constant SDIO churn.

Net effect on dmesg: after ~15s of boot, the three-line cascade stops
firing entirely. The firmware-side wedge is observed once per boot
(captured by the pm_unsupported latch) instead of per-cycle.

Signed-off-by: Markus Fritsche <fritsche.markus@gmail.com>

bes2600/bes2600_sdio.c

@@ -1388,7 +1388,14 @@ static void bes2600_gpio_wakeup_mcu(struct sbus_priv *self, int flag)
 
 	/* error check */
 	if((self->gpio_wakup_flags & BIT(flag)) != 0) {
-		bes_err(			"repeat set gpio_wake_flag, sub_sys:%d", flag);
+		/*
+		 * Multiple subsystems holding wake is the steady-state case
+		 * (e.g. WIFI + BT both want MCU awake). Demoted from bes_err
+		 * to bes_devel since it isn't an error - the GPIO is already
+		 * asserted high and the subsystem is now also tracked.
+		 */
+		bes_devel("repeat set gpio_wake_flag, sub_sys:%d\n", flag);
+		self->gpio_wakup_flags |= BIT(flag);
 		mutex_unlock(&self->io_mutex);
 		return;
 	}
@@ -1420,7 +1427,11 @@ static void bes2600_gpio_allow_mcu_sleep(struct sbus_priv *self, int flag)
 
 	/* error check */
 	if((self->gpio_wakup_flags & BIT(flag)) == 0) {
-		bes_err(			"repeat clear gpio_wake_flag, sub_sys:%d", flag);
+		/*
+		 * Mirror of the wake path: a clear when the bit is already
+		 * clear is racy bookkeeping, not a hardware error.
+		 */
+		bes_devel("repeat clear gpio_wake_flag, sub_sys:%d\n", flag);
 		mutex_unlock(&self->io_mutex);
 		return;
 	}

bes2600/bes_pwr.c

@@ -467,6 +467,45 @@ static void bes2600_pwr_device_enter_lp_mode(struct bes2600_common *hw_priv)
 	bes_devel("device enter sleep\n");
 }
 
+/*
+ * Number of consecutive bes2600_pwr_enter_lp_mode timeouts (with zero
+ * PM_INDICATIONs received) before we conclude the firmware does not
+ * honor host-driven PSM and switch to a sticky skip path.
+ */
+#define BES2600_PM_UNSUPPORTED_THRESHOLD	3
+
+/*
+ * Latch pm_unsupported = true and force chip_pm_state = ACTIVE so the
+ * c6.2 wake-side skip branch covers bes2600_pwr_device_exit_lp_mode.
+ * Called after BES2600_PM_UNSUPPORTED_THRESHOLD consecutive enter_lp_mode
+ * timeouts with zero PM_INDICATIONs.
+ */
+static void bes2600_pwr_latch_pm_unsupported(struct bes2600_common *hw_priv)
+{
+	bes_warn("PSM not honored (%u timeouts), switching to skip mode\n",
+		 hw_priv->bes_power.pm_consecutive_timeouts);
+	hw_priv->bes_power.pm_unsupported = true;
+	atomic_set(&hw_priv->bes_power.chip_pm_state,
+		   BES2600_CHIP_PM_ACTIVE);
+
+	/*
+	 * Hold the MCU wake-flag bit permanently. Without this, every
+	 * sdio_rx_work invocation hits bes2600_gpio_wakeup_mcu(SDIO_RX)
+	 * when gpio_wakup_flags == 0, drives the GPIO high and msleeps
+	 * 10 ms per RX. With ~50 RX/s of beacons + multicast that's
+	 * ~50%% of the bes_sdio workqueue thread blocked in msleep,
+	 * which directly caps RX throughput. Holding the MCU bit makes
+	 * those calls bit-only bookkeeping (gpio_wakeup = (flags == 0)
+	 * stays false, no GPIO toggle, no msleep). The bit is never
+	 * cleared once pm_unsupported is set because
+	 * bes2600_pwr_device_enter_lp_mode is unreachable under the
+	 * early-return.
+	 */
+	if (hw_priv->sbus_ops->gpio_wake)
+		hw_priv->sbus_ops->gpio_wake(hw_priv->sbus_priv,
+					     GPIO_WAKE_FLAG_MCU);
+}
+
 static int bes2600_pwr_enter_lp_mode(struct bes2600_common *hw_priv)
 {
 	int i = 0;
@@ -476,6 +515,17 @@ static int bes2600_pwr_enter_lp_mode(struct bes2600_common *hw_priv)
 	char ip_str[20];
 	unsigned long status = 0;
 
+	/*
+	 * Sticky early-return when we've previously concluded the firmware
+	 * doesn't honor PSM. Each attempt would otherwise burn 5s on a
+	 * doomed wait_for_completion_timeout and produce a noisy three-line
+	 * cascade in dmesg every time power_down_work retries (every
+	 * ~10s). The chip stays in active mode, which on this firmware is
+	 * the de-facto state anyway.
+	 */
+	if (hw_priv->bes_power.pm_unsupported)
+		return -EOPNOTSUPP;
+
 	/* set interface low power configuration */
 	bes2600_for_each_vif(hw_priv, priv, i) {
 #ifdef P2P_MULTIVIF
@@ -524,7 +574,17 @@ static int bes2600_pwr_enter_lp_mode(struct bes2600_common *hw_priv)
 				bes_devel("%s, psMode:%s, fastPsmIdlePeriod:%d apPsmChangePeriod:%d minAutoPsPollPeriod:%d\n",
 						__func__, bes2600_get_ps_mode_str(priv->powersave_mode.pmMode), priv->powersave_mode.fastPsmIdlePeriod,
 						priv->powersave_mode.apPsmChangePeriod, priv->powersave_mode.minAutoPsPollPeriod);
+				/*
+				 * Reinit BEFORE the WSM goes out, so a stale
+				 * indication from a previous cycle cannot have
+				 * primed pm_enter_cmpl. From here until the
+				 * indication callback's cmpxchg(1->0) on
+				 * pm_set_in_process, only the indication for
+				 * THIS request can complete the wait.
+				 */
+				reinit_completion(&hw_priv->bes_power.pm_enter_cmpl);
 				atomic_set(&hw_priv->bes_power.pm_set_in_process, 1);
+
 				ret = bes2600_set_pm(priv, &priv->powersave_mode);
 				if (ret) {
 					atomic_set(&hw_priv->bes_power.pm_set_in_process, 0);
@@ -535,11 +595,36 @@ static int bes2600_pwr_enter_lp_mode(struct bes2600_common *hw_priv)
 
 				/* wait power save mode changed indication */
 				status = wait_for_completion_timeout(&hw_priv->bes_power.pm_enter_cmpl, 5 * HZ);
-				atomic_set(&hw_priv->bes_power.pm_set_in_process, 0);
-				reinit_completion(&hw_priv->bes_power.pm_enter_cmpl);
 				if (!status) {
+					/*
+					 * The indication callback only fires
+					 * complete() when it observes
+					 * pm_set_in_process == 1; cmpxchg it
+					 * to 0 here so a late indication
+					 * cannot prime the next wait.
+					 *
+					 * If we win the cmpxchg, this is a
+					 * real timeout: the firmware's PS
+					 * state is unknown to us. Mark it as
+					 * such so the next wake path can
+					 * probe before assuming the chip is
+					 * still active.
+					 *
+					 * If we lose the cmpxchg, the
+					 * indication arrived between the
+					 * wait timing out and us getting
+					 * here; treat as success.
+					 */
+					if (atomic_cmpxchg(&hw_priv->bes_power.pm_set_in_process,
+							   1, 0) == 1) {
 						bes_devel("%s, wait pm ind timeout\n", __func__);
+						atomic_set(&hw_priv->bes_power.chip_pm_state,
+							   BES2600_CHIP_PM_UNKNOWN);
 						timeouts++;
+						if (++hw_priv->bes_power.pm_consecutive_timeouts
+						    >= BES2600_PM_UNSUPPORTED_THRESHOLD)
+							bes2600_pwr_latch_pm_unsupported(hw_priv);
+					}
 				}
 			} else {
 				bes_devel("skip enter lp mode\n");
@@ -554,10 +639,35 @@ static int bes2600_pwr_enter_lp_mode(struct bes2600_common *hw_priv)
 	 * in an inconsistent state that cascades into SDIO TX errors on
 	 * the BES2600.
 	 */
-	if (timeouts == 0)
+	if (timeouts == 0) {
 		bes2600_pwr_device_enter_lp_mode(hw_priv);
-	else
+	} else {
+		/*
+		 * device_enter_lp_mode() was skipped (one or more VIFs
+		 * timed out waiting for the firmware indication) so its
+		 * gpio_sleep(MCU) - which drops the wake-flag bit and, if
+		 * no other subsystem holds the wake, drives the GPIO low -
+		 * never ran. Without it the bit stays asserted, and the
+		 * next bes2600_pwr_device_exit_lp_mode() calls
+		 * gpio_wake(MCU) into a "bit already set" no-op: the GPIO
+		 * never re-edges, sbus_active() exhausts its 200x2ms
+		 * MCU_WAKEUP_READY budget against an unwoken chip, and
+		 * the first TX after idle stalls for several seconds.
+		 *
+		 * Drop the MCU wake-flag bit explicitly here so the next
+		 * wake injects a real GPIO edge. gpio_allow_mcu_sleep
+		 * preserves multi-subsystem semantics: it only drives the
+		 * GPIO low when no other subsystem still holds wake; if
+		 * BT or another holder is keeping the chip awake, the
+		 * GPIO stays high and the bit clear here is purely
+		 * bookkeeping (so the next gpio_wake doesn't no-op).
+		 */
+		if (!hw_priv->bes_power.pm_unsupported &&
+		    hw_priv->sbus_ops->gpio_sleep)
+			hw_priv->sbus_ops->gpio_sleep(hw_priv->sbus_priv,
+						      GPIO_WAKE_FLAG_MCU);
 		ret = -ETIMEDOUT;
+	}
 
 	return ret;
 }
@@ -565,19 +675,61 @@ static int bes2600_pwr_enter_lp_mode(struct bes2600_common *hw_priv)
 static void bes2600_pwr_device_exit_lp_mode(struct bes2600_common *hw_priv)
 {
 	int ret = 0;
+	enum bes2600_chip_pm_state state;
 	struct wsm_operational_mode mode = {
 		.power_mode = wsm_power_mode_active,
 		.disableMoreFlagUsage = true,
 	};
 
+	/*
+	 * Consult chip_pm_state set by bes2600_pwr_notify_ps_changed().
+	 * If we last saw the firmware confirm ACTIVE, skip ONLY the
+	 * gpio_wake + sbus_active wake handshake - the GPIO is already
+	 * asserted high and the SDIO MCU subsystem is already running,
+	 * so another sbus_active() round-trip just hits its 200x2ms
+	 * timeout because the firmware has nothing to do.
+	 *
+	 * wsm_set_operational_mode() below is NOT part of the wake
+	 * handshake; it is the operational-mode setter the firmware
+	 * tracks per call. Skipping it leaves the chip's SDIO state
+	 * machine without a fresh operational-mode update, which on
+	 * PineTab2 wedges the bus (-EBUSY on next sdio_rx_work read)
+	 * within a few seconds of probe completion. So it must run
+	 * unconditionally.
+	 */
+	state = atomic_read(&hw_priv->bes_power.chip_pm_state);
+	if (state == BES2600_CHIP_PM_ACTIVE) {
+		bes_devel("device_exit_lp_mode: chip already ACTIVE, skipping wake handshake\n");
+	} else {
 		bes_devel("host lock lmac\n");
 		if (hw_priv->sbus_ops->gpio_wake)
-		hw_priv->sbus_ops->gpio_wake(hw_priv->sbus_priv, GPIO_WAKE_FLAG_MCU);
+			hw_priv->sbus_ops->gpio_wake(hw_priv->sbus_priv,
+						      GPIO_WAKE_FLAG_MCU);
 
 		if (hw_priv->sbus_ops->sbus_active) {
-		ret = hw_priv->sbus_ops->sbus_active(hw_priv->sbus_priv, SUBSYSTEM_MCU);
-		if (ret)
+			ret = hw_priv->sbus_ops->sbus_active(hw_priv->sbus_priv,
+							     SUBSYSTEM_MCU);
+			if (ret) {
+				/*
+				 * MCU_WAKEUP_READY did not arrive within
+				 * the SDIO handshake window. Record state
+				 * as UNKNOWN so the next exit_lp_mode call
+				 * also runs the full wake sequence (no
+				 * skip), but still send operational_mode
+				 * below to match pre-c6 behaviour - the
+				 * WSM may succeed even if the SDIO active
+				 * confirm was lost, and if it fails too,
+				 * we just emit a second devel-level error.
+				 * Repeated UNKNOWN is the signal for the
+				 * LMAC active-monitor to eventually
+				 * escalate to bus_reset (c5.2's
+				 * mmc_hw_reset path).
+				 */
 				bes_err("%s, active mcu fail\n", __func__);
+				atomic_set(&hw_priv->bes_power.chip_pm_state,
+					   BES2600_CHIP_PM_UNKNOWN);
+			}
+		}
 	}
 
 	ret = wsm_set_operational_mode(hw_priv, &mode, 0);
@@ -833,6 +985,9 @@ void bes2600_pwr_init(struct bes2600_common *hw_priv)
         hw_priv->bes_power.power_up_task = NULL;
         mutex_init(&hw_priv->bes_power.pwr_mutex);
         atomic_set(&hw_priv->bes_power.dev_state, 0);
+	atomic_set(&hw_priv->bes_power.chip_pm_state, BES2600_CHIP_PM_UNKNOWN);
+	hw_priv->bes_power.pm_unsupported = false;
+	hw_priv->bes_power.pm_consecutive_timeouts = 0;
         init_completion(&hw_priv->bes_power.pm_enter_cmpl);
         sema_init(&hw_priv->bes_power.sync_lock, 1);
         device_set_wakeup_capable(hw_priv->pdev, true);
@@ -1213,9 +1368,40 @@ int bes2600_pwr_clear_busy_event(struct bes2600_common *hw_priv, u32 event)
 
 void bes2600_pwr_notify_ps_changed(struct bes2600_common *hw_priv, u8 psmode)
 {
+	/*
+	 * The firmware sends a PM-changed indication for every transition,
+	 * including ones we didn't ask for (firmware-internal coex moves,
+	 * idle-driven aging). Update chip_pm_state unconditionally so the
+	 * wake path can use it, but only fire pm_enter_cmpl when a host-
+	 * initiated set_pm is actually in flight - otherwise a stale
+	 * indication can prime a future wait against a freshly
+	 * reinit_completion()'ed state.
+	 */
+	/*
+	 * Any PM indication, whatever its psmode, proves the firmware is
+	 * actually emitting them. Reset the consecutive-timeout counter
+	 * so a transient stall doesn't permanently disable PSM, and clear
+	 * pm_unsupported if a previous run had latched it.
+	 */
+	hw_priv->bes_power.pm_consecutive_timeouts = 0;
+	if (hw_priv->bes_power.pm_unsupported) {
+		bes_warn("PM indication arrived after pm_unsupported was set; re-enabling PSM transitions\n");
+		hw_priv->bes_power.pm_unsupported = false;
+	}
+
 	if ((psmode & 0x01) != WSM_PSM_ACTIVE) {
+		atomic_set(&hw_priv->bes_power.chip_pm_state,
+			   BES2600_CHIP_PM_LP);
+		if (atomic_cmpxchg(&hw_priv->bes_power.pm_set_in_process,
+				   1, 0) == 1) {
 			bes_devel("complete pm_enter_cmpl\n");
 			complete(&hw_priv->bes_power.pm_enter_cmpl);
+		} else {
+			bes_devel("PM ind (LP) without pending wait; state recorded\n");
+		}
+	} else {
+		atomic_set(&hw_priv->bes_power.chip_pm_state,
+			   BES2600_CHIP_PM_ACTIVE);
 	}
 }
 

bes2600/bes_pwr.h

@@ -64,6 +64,20 @@ enum power_down_state
         POWER_DOWN_STATE_UNLOCKED,
 };
 
+/*
+ * Confirmed PM state of the firmware-side chip. Tracks what the host
+ * has *seen* the firmware acknowledge, not what the host has
+ * requested. UNKNOWN means a host-initiated transition timed out
+ * before the firmware indication arrived; the next wake path should
+ * treat it as "we don't know" and probe before issuing GPIO/SDIO
+ * wakeup ops.
+ */
+enum bes2600_chip_pm_state {
+	BES2600_CHIP_PM_ACTIVE = 0,
+	BES2600_CHIP_PM_LP,
+	BES2600_CHIP_PM_UNKNOWN,
+};
+
 typedef void (*bes_pwr_enter_lp_cb)(struct bes2600_common *hw_priv);
 typedef void (*bes_pwr_exit_lp_cb)(struct bes2600_common *hw_priv);
 
@@ -106,6 +120,16 @@ struct bes2600_pwr_t
         bool ap_lp_bad;
         struct bes2600_pwr_event_t pwr_events[BES2600_DELAY_EVENT_NUM];
         atomic_t pm_set_in_process;
+	atomic_t chip_pm_state;
+	/*
+	 * Sticky flag set after BES2600_PM_UNSUPPORTED_THRESHOLD
+	 * consecutive enter_lp_mode timeouts with zero PM_INDICATIONs
+	 * received from firmware. Indicates this chip's firmware does
+	 * not honor host-driven PSM transitions; further attempts are
+	 * skipped to avoid the 5s timeout cascade.
+	 */
+	bool pm_unsupported;
+	unsigned int pm_consecutive_timeouts;
 };
 
 #ifdef CONFIG_BES2600_WOWLAN

bes2600/scan.c

@@ -14,11 +14,63 @@
 #include "scan.h"
 #include "sta.h"
 #include "pm.h"
+#include "epta_coex.h"
 #include "epta_request.h"
 #include "bes_pwr.h"
 
+/*
+ * After this many consecutive WSM scan rejections from firmware, stop
+ * issuing new scans for BES2600_SCAN_BACKOFF_JIFFIES and let the state
+ * that's rejecting them (coex window, firmware-internal busy) clear.
+ *
+ * The backoff has to be at least as long as the natural mac80211 scan-
+ * retry cadence, otherwise the next attempt lands outside the window
+ * and bypasses the defer guard. Observed in the wild on PineTab2:
+ * roam-evaluation bursts at ~12 s cadence, idle background scans at
+ * ~5 min cadence. 30 s catches the burst and leaves the slow case
+ * alone (the firmware-policy state has had minutes to clear by then
+ * anyway).
+ */
+#define BES2600_SCAN_REJECT_THRESHOLD	3
+#define BES2600_SCAN_BACKOFF_JIFFIES	(30 * HZ)
+
 static void bes2600_scan_restart_delayed(struct bes2600_vif *priv);
 
+/*
+ * Decide whether to skip sending the next WSM scan command without
+ * bothering the firmware. Two triggers:
+ *
+ *  1. BT A2DP is streaming in non-FDD coex mode. The firmware is
+ *     known to reject scan requests during that window; short-
+ *     circuiting here saves a WSM round-trip and avoids the
+ *     wsm_generic_confirm / scan_work warning cascade that follows.
+ *
+ *  2. We already saw >= BES2600_SCAN_REJECT_THRESHOLD consecutive
+ *     rejections on recent scan attempts and the backoff window has
+ *     not yet elapsed. Whatever was rejecting them is likely still
+ *     rejecting them; give it time. If the backoff has elapsed without
+ *     a fresh reject refreshing it, the burst is over and we reset the
+ *     count so an isolated reject doesn't immediately re-trip.
+ *
+ * Returns true if the caller should abandon the scan iteration.
+ */
+static bool bes2600_scan_should_defer(struct bes2600_common *hw_priv)
+{
+#ifdef WIFI_BT_COEXIST_EPTA_ENABLE
+	if (!coex_is_fdd_mode() && coex_is_bt_a2dp())
+		return true;
+#endif
+
+	if (time_after(jiffies, hw_priv->scan.backoff_until))
+		hw_priv->scan.reject_count = 0;
+
+	if (hw_priv->scan.reject_count >= BES2600_SCAN_REJECT_THRESHOLD &&
+	    time_before(jiffies, hw_priv->scan.backoff_until))
+		return true;
+
+	return false;
+}
+
 #ifdef CONFIG_BES2600_TESTMODE
 static int bes2600_advance_scan_start(struct bes2600_common *hw_priv)
 {
@@ -702,10 +754,29 @@ void bes2600_scan_work(struct work_struct *work)
 				wsm_unlock_tx(hw_priv);
 		} else
 #endif
-			hw_priv->scan.status = bes2600_scan_start(priv, &scan);
+		{
+			if (bes2600_scan_should_defer(hw_priv)) {
+				hw_priv->scan.status = -EBUSY;
+				hw_priv->scan.reject_count++;
+				hw_priv->scan.backoff_until =
+					jiffies + BES2600_SCAN_BACKOFF_JIFFIES;
+				wiphy_dbg(priv->hw->wiphy,
+					  "[SCAN] deferred (coex/backoff, reject_count=%u)\n",
+					  hw_priv->scan.reject_count);
 				kfree(scan.ch);
-		if (WARN_ON(hw_priv->scan.status))
 				goto fail;
+			}
+			hw_priv->scan.status = bes2600_scan_start(priv, &scan);
+		}
+		kfree(scan.ch);
+		if (hw_priv->scan.status) {
+			hw_priv->scan.reject_count++;
+			hw_priv->scan.backoff_until =
+				jiffies + BES2600_SCAN_BACKOFF_JIFFIES;
+			/* Lower callers already logged the reason at wiphy_warn. */
+			goto fail;
+		}
+		hw_priv->scan.reject_count = 0;
 		hw_priv->scan.curr = it;
 	}
 	up(&hw_priv->conf_lock);

bes2600/scan.h

@@ -42,6 +42,17 @@ struct bes2600_scan {
 	struct delayed_work probe_work;
 	int direct_probe;
 	u8 if_id;
+	/*
+	 * Track consecutive firmware-side WSM scan rejections so we can
+	 * back off briefly instead of re-issuing the same scan on every
+	 * mac80211 background-scan tick. Firmware returns WSM status != 0
+	 * for a handful of transient conditions (BT A2DP active in non-
+	 * FDD coex, firmware-internal busy windows) and keeps rejecting
+	 * until the state clears; retrying at full cadence just floods
+	 * dmesg.
+	 */
+	unsigned int reject_count;
+	unsigned long backoff_until;
 };
 
 int bes2600_hw_scan(struct ieee80211_hw *hw,

bes2600/wsm.c

@@ -134,8 +134,20 @@ static int wsm_generic_confirm(struct bes2600_common *hw_priv,
 				 struct wsm_buf *buf)
 {
 	u32 status = WSM_GET32(buf);
-	if (WARN(status != WSM_STATUS_SUCCESS, "wsm_generic_confirm ret %u", status))
+
+	/*
+	 * A non-SUCCESS status here is a firmware-side policy decision for
+	 * the command whose confirm this is -- commonly WSM status 2 for
+	 * scan (0x0407) rejected because of a coex window or transient
+	 * firmware-busy state. It is not a driver/kernel bug, so avoid the
+	 * WARN()/stack-trace treatment; the caller already emits a
+	 * wiphy_warn identifying the request id and will propagate the
+	 * error to mac80211.
+	 */
+	if (status != WSM_STATUS_SUCCESS) {
+		bes_devel("%s ret %u\n", __func__, status);
 		return -EINVAL;
+	}
 	return 0;
 
 underflow: