[RFC 2/2] ath9k: Reset chip on potential deaf state

[Sven Eckelmann <sven.eckelmann@open-mesh.com>]

From: Simon Wunderlich <simon.wunderlich@open-mesh.com>

The chip is switching seemingly random into a state which can be described
as "deaf". No or nearly no interrupts are generated anymore for incoming
packets. Existing links either break down after a while and new links will
not be established.

The driver doesn't know if there is no other device available or if it
ended up in an "deaf" state. Resetting the chip proactively avoids
permanent problems in case the chip really was in its "deaf" state but
maybe causes unnecessary resets in case it wasn't "deaf".

Signed-off-by: Simon Wunderlich <simon.wunderlich@open-mesh.com>
[sven.eckelmann@open-mesh.com: port to recent ath9k, add commit message]
Signed-off-by: Sven Eckelmann <sven.eckelmann@open-mesh.com>
---
This problem was discovered in mesh setups. It was noticed that some nodes
were not able to see their neighbors (mostly after running for a while) -
even when those neighbors received data from them via IBSS. A simple `iw
dev wlan0 scan` fixed the problem for them. But the problem seems to
reappear after while(tm) in a large enough(tm) mesh.

This patch is a little bit obscure because it requires CONFIG_ATH9K_DEBUGFS
to actually work. But there still seems to be potential interest in
Freifunk communities or Freifunk meta-projects (e.g. freifunk-gluon). It is
currently not known if it helps them but publishing this to allow them to
test and play around with it will not hurt :)
---
 drivers/net/wireless/ath/ath9k/ath9k.h |  3 +++
 drivers/net/wireless/ath/ath9k/debug.c |  1 +
 drivers/net/wireless/ath/ath9k/debug.h |  1 +
 drivers/net/wireless/ath/ath9k/link.c  | 45 ++++++++++++++++++++++++++++++++++
 4 files changed, 50 insertions(+)

diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index 9c6fee7..3987ad5 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -996,6 +996,9 @@ struct ath_softc {
 	short nbcnvifs;
 	unsigned long ps_usecount;
 
+	unsigned long last_check_time;
+	u32 last_check_interrupts;
+
 	struct ath_rx rx;
 	struct ath_tx tx;
 	struct ath_beacon beacon;
diff --git a/drivers/net/wireless/ath/ath9k/debug.c b/drivers/net/wireless/ath/ath9k/debug.c
index 608b370..6d5c253 100644
--- a/drivers/net/wireless/ath/ath9k/debug.c
+++ b/drivers/net/wireless/ath/ath9k/debug.c
@@ -768,6 +768,7 @@ static int read_file_reset(struct seq_file *file, void *data)
 		[RESET_TX_DMA_ERROR] = "Tx DMA stop error",
 		[RESET_RX_DMA_ERROR] = "Rx DMA stop error",
 		[RESET_TYPE_DEADBEEF] = "deadbeef hang",
+		[RESET_TYPE_DEAF] = "deaf hang",
 	};
 	int i;
 
diff --git a/drivers/net/wireless/ath/ath9k/debug.h b/drivers/net/wireless/ath/ath9k/debug.h
index 0d77abbf6..6f186bd 100644
--- a/drivers/net/wireless/ath/ath9k/debug.h
+++ b/drivers/net/wireless/ath/ath9k/debug.h
@@ -53,6 +53,7 @@ enum ath_reset_type {
 	RESET_TX_DMA_ERROR,
 	RESET_RX_DMA_ERROR,
 	RESET_TYPE_DEADBEEF,
+	RESET_TYPE_DEAF,
 	__RESET_TYPE_MAX
 };
 
diff --git a/drivers/net/wireless/ath/ath9k/link.c b/drivers/net/wireless/ath/ath9k/link.c
index ff11d85..f4b74b7 100644
--- a/drivers/net/wireless/ath/ath9k/link.c
+++ b/drivers/net/wireless/ath/ath9k/link.c
@@ -158,6 +158,48 @@ static bool ath_hw_hang_deadbeef(struct ath_softc *sc)
 	return true;
 }
 
+static bool ath_hw_hang_deaf(struct ath_softc *sc)
+{
+#ifndef CONFIG_ATH9K_DEBUGFS
+	return false;
+#else
+	struct ath_common *common = ath9k_hw_common(sc->sc_ah);
+	u32 interrupts, interrupt_per_s;
+	unsigned int interval;
+
+	/* get historic data */
+	interval = jiffies_to_msecs(jiffies - sc->last_check_time);
+	if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_EDMA)
+		interrupts = sc->debug.stats.istats.rxlp;
+	else
+		interrupts = sc->debug.stats.istats.rxok;
+
+	interrupts -= sc->last_check_interrupts;
+
+	/* save current data */
+	sc->last_check_time = jiffies;
+	if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_EDMA)
+		sc->last_check_interrupts = sc->debug.stats.istats.rxlp;
+	else
+		sc->last_check_interrupts = sc->debug.stats.istats.rxok;
+
+	/* sanity check, should be 30 seconds */
+	if (interval > 40000 || interval < 20000)
+		return false;
+
+	/* should be at least one interrupt per second */
+	interrupt_per_s = interrupts / (interval / 1000);
+	if (interrupt_per_s >= 1)
+		return false;
+
+	ath_dbg(common, RESET,
+		"RX deaf hang is detected. Schedule chip reset\n");
+	ath9k_queue_reset(sc, RESET_TYPE_DEAF);
+
+	return true;
+#endif
+}
+
 void ath_hw_hang_work(struct work_struct *work)
 {
 	struct ath_softc *sc = container_of(work, struct ath_softc,
@@ -166,6 +208,9 @@ void ath_hw_hang_work(struct work_struct *work)
 	if (ath_hw_hang_deadbeef(sc))
 		goto requeue_worker;
 
+	if (ath_hw_hang_deaf(sc))
+		goto requeue_worker;
+
 requeue_worker:
 	ieee80211_queue_delayed_work(sc->hw, &sc->hw_hang_work,
 				     msecs_to_jiffies(ATH_HANG_WORK_INTERVAL));
-- 
2.10.2