ath9k: Process GTT interrupts

Global Transmission Timeout interrupts are generated by
the HW when transmission of a frame fails - this is done
based on the threshold programmed in the AR_GTXTO register.

Currently, even though the interrupt is enabled for all chips,
it is not handled in the driver. This patch handles GTT events
for AR9003 and above chips, checking if the MAC/BB has hung
after successive GTT interrupts crosses a threshold (5).

This can be enabled for the older chips in the AR9002 family once
appropriate HW hang checks are implemented for them.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/ath9k.h

@@ -691,6 +691,7 @@ void ath_ant_comb_scan(struct ath_softc *sc, struct ath_rx_status *rs);
 #define DEFAULT_CACHELINE       32
 #define ATH_CABQ_READY_TIME     80      /* % of beacon interval */
 #define ATH_TXPOWER_MAX         100     /* .5 dBm units */
+#define MAX_GTT_CNT             5
 
 enum sc_op_flags {
 	SC_OP_INVALID,
@@ -733,6 +734,7 @@ struct ath_softc {
 	unsigned long sc_flags;
 	unsigned long driver_data;
 
+	u8 gtt_cnt;
 	u32 intrstatus;
 	u16 ps_flags; /* PS_* */
 	u16 curtxpow;

drivers/net/wireless/ath/ath9k/debug.h

@@ -44,6 +44,7 @@ enum ath_reset_type {
 	RESET_TYPE_BB_WATCHDOG,
 	RESET_TYPE_FATAL_INT,
 	RESET_TYPE_TX_ERROR,
+	RESET_TYPE_TX_GTT,
 	RESET_TYPE_TX_HANG,
 	RESET_TYPE_PLL_HANG,
 	RESET_TYPE_MAC_HANG,

drivers/net/wireless/ath/ath9k/main.c

@@ -258,6 +258,7 @@ static bool ath_complete_reset(struct ath_softc *sc, bool start)
 		}
 	}
 
+	sc->gtt_cnt = 0;
 	ieee80211_wake_queues(sc->hw);
 
 	return true;
@@ -476,6 +477,19 @@ void ath9k_tasklet(unsigned long data)
 		}
 	}
 
+	if (status & ATH9K_INT_GTT) {
+		sc->gtt_cnt++;
+
+		if ((sc->gtt_cnt >= MAX_GTT_CNT) && !ath9k_hw_check_alive(ah)) {
+			type = RESET_TYPE_TX_GTT;
+			ath9k_queue_reset(sc, type);
+			atomic_inc(&ah->intr_ref_cnt);
+			ath_dbg(common, ANY,
+				"GTT: Skipping interrupts\n");
+			goto out;
+		}
+	}
+
 	spin_lock_irqsave(&sc->sc_pm_lock, flags);
 	if ((status & ATH9K_INT_TSFOOR) && sc->ps_enabled) {
 		/*
@@ -503,10 +517,19 @@ void ath9k_tasklet(unsigned long data)
 	}
 
 	if (status & ATH9K_INT_TX) {
-		if (ah->caps.hw_caps & ATH9K_HW_CAP_EDMA)
+		if (ah->caps.hw_caps & ATH9K_HW_CAP_EDMA) {
+			/*
+			 * For EDMA chips, TX completion is enabled for the
+			 * beacon queue, so if a beacon has been transmitted
+			 * successfully after a GTT interrupt, the GTT counter
+			 * gets reset to zero here.
+			 */
+			/* sc->gtt_cnt = 0; */
+
 			ath_tx_edma_tasklet(sc);
-		else
+		} else {
 			ath_tx_tasklet(sc);
+		}
 
 		wake_up(&sc->tx_wait);
 	}
@@ -536,6 +559,7 @@ irqreturn_t ath_isr(int irq, void *dev)
 		ATH9K_INT_TX |			\
 		ATH9K_INT_BMISS |		\
 		ATH9K_INT_CST |			\
+		ATH9K_INT_GTT |			\
 		ATH9K_INT_TSFOOR |		\
 		ATH9K_INT_GENTIMER |		\
 		ATH9K_INT_MCI)
@@ -608,7 +632,6 @@ irqreturn_t ath_isr(int irq, void *dev)
 	}
 #endif
 
-
 	if (status & ATH9K_INT_SWBA)
 		tasklet_schedule(&sc->bcon_tasklet);
 
@@ -733,7 +756,12 @@ static int ath9k_start(struct ieee80211_hw *hw)
 	if (ah->config.hw_hang_checks & HW_BB_WATCHDOG)
 		ah->imask |= ATH9K_INT_BB_WATCHDOG;
 
-	ah->imask |= ATH9K_INT_GTT;
+	/*
+	 * Enable GTT interrupts only for AR9003/AR9004 chips
+	 * for now.
+	 */
+	if (AR_SREV_9300_20_OR_LATER(ah))
+		ah->imask |= ATH9K_INT_GTT;
 
 	if (ah->caps.hw_caps & ATH9K_HW_CAP_HT)
 		ah->imask |= ATH9K_INT_CST;