wcn36xx: Fix/improve tx_status mechanism

- Do not stop queue for NO_ACk tx-status packets
- Do not start the ack timeout before dma transfer completion
  => skb data possibly accessed by device during timeout/release.
- paranoia checking of the skb tx ack pointer
- Do not track skb reference before skb is dequeued (preventing
possible double free in dxe_deinit)

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>

2 files changed, 21 insertions, 46 deletions

diff --git a/drivers/net/wireless/ath/wcn36xx/dxe.c b/drivers/net/wireless/ath/wcn36xx/dxe.c
index 8e1dbfda65386..7c152687027f7 100644
--- a/drivers/net/wireless/ath/wcn36xx/dxe.c
+++ b/drivers/net/wireless/ath/wcn36xx/dxe.c
@@ -403,8 +403,21 @@ static void reap_tx_dxes(struct wcn36xx *wcn, struct wcn36xx_dxe_ch *ch)
 			dma_unmap_single(wcn->dev, ctl->desc->src_addr_l,
 					 ctl->skb->len, DMA_TO_DEVICE);
 			info = IEEE80211_SKB_CB(ctl->skb);
-			if (!(info->flags & IEEE80211_TX_CTL_REQ_TX_STATUS)) {
-				/* Keep frame until TX status comes */
+			if (info->flags & IEEE80211_TX_CTL_REQ_TX_STATUS) {
+				if (info->flags & IEEE80211_TX_CTL_NO_ACK) {
+					info->flags |= IEEE80211_TX_STAT_NOACK_TRANSMITTED;
+					ieee80211_tx_status_irqsafe(wcn->hw, ctl->skb);
+				} else {
+					/* Wait for the TX ack indication or timeout... */
+					spin_lock(&wcn->dxe_lock);
+					if (WARN_ON(wcn->tx_ack_skb))
+						ieee80211_free_txskb(wcn->hw, wcn->tx_ack_skb);
+					wcn->tx_ack_skb = ctl->skb; /* Tracking ref */
+					mod_timer(&wcn->tx_ack_timer, jiffies + HZ / 10);
+					spin_unlock(&wcn->dxe_lock);
+				}
+				/* do not free, ownership transfered to mac80211 status cb */
+			} else {
 				ieee80211_free_txskb(wcn->hw, ctl->skb);
 			}
 
@@ -426,7 +439,6 @@ static irqreturn_t wcn36xx_irq_tx_complete(int irq, void *dev)
 {
 	struct wcn36xx *wcn = (struct wcn36xx *)dev;
 	int int_src, int_reason;
-	bool transmitted = false;
 
 	wcn36xx_dxe_read_register(wcn, WCN36XX_DXE_INT_SRC_RAW_REG, &int_src);
 
@@ -466,7 +478,6 @@ static irqreturn_t wcn36xx_irq_tx_complete(int irq, void *dev)
 		if (int_reason & (WCN36XX_CH_STAT_INT_DONE_MASK |
 				  WCN36XX_CH_STAT_INT_ED_MASK)) {
 			reap_tx_dxes(wcn, &wcn->dxe_tx_h_ch);
-			transmitted = true;
 		}
 	}
 
@@ -479,7 +490,6 @@ static irqreturn_t wcn36xx_irq_tx_complete(int irq, void *dev)
 					   WCN36XX_DXE_0_INT_CLR,
 					   WCN36XX_INT_MASK_CHAN_TX_L);
 
-
 		if (int_reason & WCN36XX_CH_STAT_INT_ERR_MASK ) {
 			wcn36xx_dxe_write_register(wcn,
 						   WCN36XX_DXE_0_INT_ERR_CLR,
@@ -507,25 +517,8 @@ static irqreturn_t wcn36xx_irq_tx_complete(int irq, void *dev)
 		if (int_reason & (WCN36XX_CH_STAT_INT_DONE_MASK |
 				  WCN36XX_CH_STAT_INT_ED_MASK)) {
 			reap_tx_dxes(wcn, &wcn->dxe_tx_l_ch);
-			transmitted = true;
-		}
-	}
-
-	spin_lock(&wcn->dxe_lock);
-	if (wcn->tx_ack_skb && transmitted) {
-		struct ieee80211_tx_info *info = IEEE80211_SKB_CB(wcn->tx_ack_skb);
-
-		/* TX complete, no need to wait for 802.11 ack indication */
-		if (info->flags & IEEE80211_TX_CTL_REQ_TX_STATUS &&
-		    info->flags & IEEE80211_TX_CTL_NO_ACK) {
-			info->flags |= IEEE80211_TX_STAT_NOACK_TRANSMITTED;
-			del_timer(&wcn->tx_ack_timer);
-			ieee80211_tx_status_irqsafe(wcn->hw, wcn->tx_ack_skb);
-			wcn->tx_ack_skb = NULL;
-			ieee80211_wake_queues(wcn->hw);
 		}
 	}
-	spin_unlock(&wcn->dxe_lock);
 
 	return IRQ_HANDLED;
 }
diff --git a/drivers/net/wireless/ath/wcn36xx/txrx.c b/drivers/net/wireless/ath/wcn36xx/txrx.c
index 40f59b656205e..ef09bdcc32a18 100644
--- a/drivers/net/wireless/ath/wcn36xx/txrx.c
+++ b/drivers/net/wireless/ath/wcn36xx/txrx.c
@@ -592,6 +592,8 @@ int wcn36xx_start_tx(struct wcn36xx *wcn,
 	bool is_low = ieee80211_is_data(hdr->frame_control);
 	bool bcast = is_broadcast_ether_addr(hdr->addr1) ||
 		is_multicast_ether_addr(hdr->addr1);
+	bool ack_ind = (info->flags & IEEE80211_TX_CTL_REQ_TX_STATUS) &&
+					!(info->flags & IEEE80211_TX_CTL_NO_ACK);
 	struct wcn36xx_tx_bd bd;
 	int ret;
 
@@ -607,30 +609,16 @@ int wcn36xx_start_tx(struct wcn36xx *wcn,
 
 	bd.dpu_rf = WCN36XX_BMU_WQ_TX;
 
-	if (info->flags & IEEE80211_TX_CTL_REQ_TX_STATUS) {
+	if (unlikely(ack_ind)) {
 		wcn36xx_dbg(WCN36XX_DBG_DXE, "TX_ACK status requested\n");
 
-		spin_lock_irqsave(&wcn->dxe_lock, flags);
-		if (wcn->tx_ack_skb) {
-			spin_unlock_irqrestore(&wcn->dxe_lock, flags);
-			wcn36xx_warn("tx_ack_skb already set\n");
-			return -EINVAL;
-		}
-
-		wcn->tx_ack_skb = skb;
-		spin_unlock_irqrestore(&wcn->dxe_lock, flags);
-
 		/* Only one at a time is supported by fw. Stop the TX queues
 		 * until the ack status gets back.
 		 */
 		ieee80211_stop_queues(wcn->hw);
 
-		/* TX watchdog if no TX irq or ack indication received  */
-		mod_timer(&wcn->tx_ack_timer, jiffies + HZ / 10);
-
 		/* Request ack indication from the firmware */
-		if (!(info->flags & IEEE80211_TX_CTL_NO_ACK))
-			bd.tx_comp = 1;
+		bd.tx_comp = 1;
 	}
 
 	/* Data frames served first*/
@@ -644,14 +632,8 @@ int wcn36xx_start_tx(struct wcn36xx *wcn,
 	bd.tx_bd_sign = 0xbdbdbdbd;
 
 	ret = wcn36xx_dxe_tx_frame(wcn, vif_priv, &bd, skb, is_low);
-	if (ret && (info->flags & IEEE80211_TX_CTL_REQ_TX_STATUS)) {
-		/* If the skb has not been transmitted,
-		 * don't keep a reference to it.
-		 */
-		spin_lock_irqsave(&wcn->dxe_lock, flags);
-		wcn->tx_ack_skb = NULL;
-		spin_unlock_irqrestore(&wcn->dxe_lock, flags);
-
+	if (unlikely(ret && ack_ind)) {
+		/* If the skb has not been transmitted, resume TX queue */
 		ieee80211_wake_queues(wcn->hw);
 	}