ps3: tx descriptor handling cleanup

gelic: TX descriptor handling cleanup

        - Emitted return value of NETDEV_TX_LOCKED when DMA map or kick
          failure.
          Now it would free the skb, update drop packet statistics
          and return OK. Requested from Jeff Garzik.
        - Enable tx queue if number of free descriptors are more than 2
        - Fixed descriptor leak if dma map for second descriptor failed
        - Stopped calling xmit handler from interrupt handler in order
          to recheck tx queue.  Instead, call appropriate helper functions.
Signed-off-by: Masakazu Mokuno <mokuno@sm.sony.co.jp>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/ps3_gelic_net.c

@@ -408,22 +408,25 @@ static void gelic_net_release_tx_chain(struct gelic_net_card *card, int stop)
 			break;
 
 		case GELIC_NET_DESCR_COMPLETE:
+			if (tx_chain->tail->skb) {
 				card->netdev_stats.tx_packets++;
 				card->netdev_stats.tx_bytes +=
 					tx_chain->tail->skb->len;
+			}
 			break;
 
 		case GELIC_NET_DESCR_CARDOWNED:
 			/* pending tx request */
 		default:
 			/* any other value (== GELIC_NET_DESCR_NOT_IN_USE) */
+			if (!stop)
 				goto out;
 		}
 		gelic_net_release_tx_descr(card, tx_chain->tail);
-		release = 1;
+		release ++;
 	}
 out:
-	if (!stop && release)
+	if (!stop && (2 < release))
 		netif_wake_queue(card->netdev);
 }
 
@@ -660,19 +663,21 @@ static int gelic_net_prepare_tx_descr_v(struct gelic_net_card *card,
 {
 	dma_addr_t buf[2];
 	unsigned int vlan_len;
+	struct gelic_net_descr *sec_descr = descr->next;
 
 	if (skb->len < GELIC_NET_VLAN_POS)
 		return -EINVAL;
 
-	memcpy(&descr->vlan, skb->data, GELIC_NET_VLAN_POS);
+	vlan_len = GELIC_NET_VLAN_POS;
+	memcpy(&descr->vlan, skb->data, vlan_len);
 	if (card->vlan_index != -1) {
+		/* internal vlan tag used */
 		descr->vlan.h_vlan_proto = htons(ETH_P_8021Q); /* vlan 0x8100*/
 		descr->vlan.h_vlan_TCI = htons(card->vlan_id[card->vlan_index]);
-		vlan_len = GELIC_NET_VLAN_POS + VLAN_HLEN; /* VLAN_HLEN=4 */
-	} else
-		vlan_len = GELIC_NET_VLAN_POS; /* no vlan tag */
+		vlan_len += VLAN_HLEN; /* added for above two lines */
+	}
 
-	/* first descr */
+	/* map data area */
 	buf[0] = dma_map_single(ctodev(card), &descr->vlan,
 			     vlan_len, DMA_TO_DEVICE);
 
@@ -683,20 +688,6 @@ static int gelic_net_prepare_tx_descr_v(struct gelic_net_card *card,
 		return -ENOMEM;
 	}
 
-	descr->buf_addr = buf[0];
-	descr->buf_size = vlan_len;
-	descr->skb = skb; /* not used */
-	descr->data_status = 0;
-	gelic_net_set_txdescr_cmdstat(descr, skb, 1); /* not the frame end */
-
-	/* second descr */
-	card->tx_chain.head = card->tx_chain.head->next;
-	descr->next_descr_addr = descr->next->bus_addr;
-	descr = descr->next;
-	if (gelic_net_get_descr_status(descr) != GELIC_NET_DESCR_NOT_IN_USE)
-		/* XXX will be removed */
-		dev_err(ctodev(card), "descr is not free!\n");
-
 	buf[1] = dma_map_single(ctodev(card), skb->data + GELIC_NET_VLAN_POS,
 			     skb->len - GELIC_NET_VLAN_POS,
 			     DMA_TO_DEVICE);
@@ -711,13 +702,24 @@ static int gelic_net_prepare_tx_descr_v(struct gelic_net_card *card,
 		return -ENOMEM;
 	}
 
-	descr->buf_addr = buf[1];
-	descr->buf_size = skb->len - GELIC_NET_VLAN_POS;
-	descr->skb = skb;
+	/* first descr */
+	descr->buf_addr = buf[0];
+	descr->buf_size = vlan_len;
+	descr->skb = NULL; /* not used */
 	descr->data_status = 0;
-	descr->next_descr_addr = 0; /* terminate hw descr */
-	gelic_net_set_txdescr_cmdstat(descr, skb, 0);
+	descr->next_descr_addr = descr->next->bus_addr;
+	gelic_net_set_txdescr_cmdstat(descr, skb, 1); /* not the frame end */
 
+	/* second descr */
+	sec_descr->buf_addr = buf[1];
+	sec_descr->buf_size = skb->len - GELIC_NET_VLAN_POS;
+	sec_descr->skb = skb;
+	sec_descr->data_status = 0;
+	sec_descr->next_descr_addr = 0; /* terminate hw descr */
+	gelic_net_set_txdescr_cmdstat(sec_descr, skb, 0);
+
+	/* bump free descriptor pointer */
+	card->tx_chain.head = sec_descr->next;
 	return 0;
 }
 
@@ -730,7 +732,7 @@ static int gelic_net_prepare_tx_descr_v(struct gelic_net_card *card,
 static int gelic_net_kick_txdma(struct gelic_net_card *card,
 				struct gelic_net_descr *descr)
 {
-	int status = -ENXIO;
+	int status = 0;
 	int count = 10;
 
 	if (card->tx_dma_progress)
@@ -764,47 +766,62 @@ static int gelic_net_kick_txdma(struct gelic_net_card *card,
 static int gelic_net_xmit(struct sk_buff *skb, struct net_device *netdev)
 {
 	struct gelic_net_card *card = netdev_priv(netdev);
-	struct gelic_net_descr *descr = NULL;
+	struct gelic_net_descr *descr;
 	int result;
 	unsigned long flags;
 
 	spin_lock_irqsave(&card->tx_dma_lock, flags);
 
 	gelic_net_release_tx_chain(card, 0);
-	if (!skb)
-		goto kick;
+
 	descr = gelic_net_get_next_tx_descr(card);
 	if (!descr) {
+		/*
+		 * no more descriptors free
+		 */
 		netif_stop_queue(netdev);
 		spin_unlock_irqrestore(&card->tx_dma_lock, flags);
 		return NETDEV_TX_BUSY;
 	}
-	result = gelic_net_prepare_tx_descr_v(card, descr, skb);
 
-	if (result)
-		goto error;
-
-	card->tx_chain.head = card->tx_chain.head->next;
-
-	if (descr->prev)
+	result = gelic_net_prepare_tx_descr_v(card, descr, skb);
+	if (result) {
+		/*
+		 * DMA map failed.  As chanses are that failure
+		 * would continue, just release skb and return
+		 */
+		card->netdev_stats.tx_dropped++;
+		dev_kfree_skb_any(skb);
+		spin_unlock_irqrestore(&card->tx_dma_lock, flags);
+		return NETDEV_TX_OK;
+	}
+	/*
+	 * link this prepared descriptor to previous one
+	 * to achieve high performance
+	 */
 	descr->prev->next_descr_addr = descr->bus_addr;
-kick:
 	/*
 	 * as hardware descriptor is modified in the above lines,
 	 * ensure that the hardware sees it
 	 */
 	wmb();
-	if (gelic_net_kick_txdma(card, card->tx_chain.tail))
-		goto error;
-
+	if (gelic_net_kick_txdma(card, descr)) {
+		/*
+		 * kick failed.
+		 * release descriptors which were just prepared
+		 */
+		card->netdev_stats.tx_dropped++;
+		gelic_net_release_tx_descr(card, descr);
+		gelic_net_release_tx_descr(card, descr->next);
+		card->tx_chain.tail = descr->next->next;
+		dev_info(ctodev(card), "%s: kick failure\n", __func__);
+	} else {
+		/* OK, DMA started/reserved */
 		netdev->trans_start = jiffies;
-	spin_unlock_irqrestore(&card->tx_dma_lock, flags);
-	return NETDEV_TX_OK;
+	}
 
-error:
-	card->netdev_stats.tx_dropped++;
 	spin_unlock_irqrestore(&card->tx_dma_lock, flags);
-	return NETDEV_TX_LOCKED;
+	return NETDEV_TX_OK;
 }
 
 /**
@@ -1025,9 +1042,10 @@ static irqreturn_t gelic_net_interrupt(int irq, void *ptr)
 	if (status & GELIC_NET_TXINT) {
 		spin_lock_irqsave(&card->tx_dma_lock, flags);
 		card->tx_dma_progress = 0;
+		gelic_net_release_tx_chain(card, 0);
+		/* kick outstanding tx descriptor if any */
+		gelic_net_kick_txdma(card, card->tx_chain.tail);
 		spin_unlock_irqrestore(&card->tx_dma_lock, flags);
-		/* start pending DMA */
-		gelic_net_xmit(NULL, netdev);
 	}
 	return IRQ_HANDLED;
 }