fec.c.patch1

实现一个网卡到内存空间的零拷贝程序

--- fec.c.orig	Wed May 23 10:00:28 2001
+++ fec.c	Wed May 23 12:47:49 2001
@@ -23,14 +23,21 @@
  * Make use of MII for PHY control configurable.
  * Some fixes.
  * Copyright (c) 2000 Wolfgang Denk, DENX Software Engineering.
+ *
+ * Experimental support for scatter/gather.
+ * Joris van Rantwijk, May 2001.
  */
 
 /* List of PHYs we wish to support.
 */
-#undef	CONFIG_FEC_LXT970
-#define	CONFIG_FEC_LXT971
+#define	CONFIG_FEC_LXT970
+#undef	CONFIG_FEC_LXT971
 #undef	CONFIG_FEC_QS6612
 
+#if defined(CONFIG_FEC_SUPPORT_SG) && !defined(CONFIG_ENET_BIG_BUFFERS)
+#error "Must use big buffers for scatter/gather support on MPC8xx FEC"
+#endif
+
 #include <linux/config.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
@@ -163,6 +170,7 @@
 	scc_t	*sccp;
 	struct	net_device_stats stats;
 	uint	tx_full;
+	uint	tx_ring_len;
 	spinlock_t lock;
 
 #ifdef	CONFIG_USE_MDIO
@@ -381,11 +389,50 @@
 	fep->stats.tx_bytes += skb->len;
 	fep->skb_cur = (fep->skb_cur+1) & TX_RING_MOD_MASK;
 
+#ifdef CONFIG_FEC_SUPPORT_SG
+	if (skb_shinfo(skb)->nr_frags > 0) {
+		/* Put additional fragments in seperate buffers */
+
+		skb_frag_t *frag = skb_shinfo(skb)->frags;
+		volatile cbd_t *fbdp = bdp;
+		int i;
+
+		/* Note: skb->len is total length including all fragments */
+		bdp->cbd_datlen -= skb->data_len;
+		flush_dcache_range((unsigned long)skb->data,
+		                   (unsigned long)skb->data + skb->len - skb->data_len);
+
+		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++, frag++) {
+			unsigned long faddr = (unsigned long) page_address(frag->page) + frag->page_offset;
+			unsigned long flen = frag->size;
+
+			/* Get next BD, wrap around end */
+			if (fbdp->cbd_sc & BD_ENET_TX_WRAP)
+				fbdp = fep->tx_bd_base;
+			else
+				fbdp++;
+#ifndef final_version
+			if (fbdp->cbd_sc & BD_ENET_TX_READY)
+				printk(KERN_CRIT "fec: rhaaa: tx BD ring full\n");
+#endif
+			/* Clear all of the status flags. */
+			fbdp->cbd_sc &= ~BD_ENET_TX_STATS;
+
+			/* Set buffer length and buffer pointer. */
+			fbdp->cbd_bufaddr = __pa(faddr);
+			fbdp->cbd_datlen = flen;
+
+			/* Push the data cache. */
+			flush_dcache_range(faddr, faddr + flen);
+		}
+	} else /* WATCH OUT FOR THIS ELSE */
+#endif
 	/* Push the data cache so the CPM does not get stale memory
 	 * data.
 	 */
 	flush_dcache_range((unsigned long)skb->data,
 			   (unsigned long)skb->data + skb->len);
+/* END IF FRAGMENTS */
 
 	spin_lock_irq(&fep->lock);
 
@@ -393,6 +440,19 @@
 	 * its the last BD of the frame, and to put the CRC on the end.
 	 */
 
+#ifdef CONFIG_FEC_SUPPORT_SG
+	if (skb_shinfo(skb)->nr_frags > 0) {
+		int i;
+		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+			bdp->cbd_sc |= (BD_ENET_TX_READY | BD_ENET_TX_INTR);
+			if (bdp->cbd_sc & BD_ENET_TX_WRAP)
+				bdp = fep->tx_bd_base;
+			else
+				bdp++;
+			fep->tx_ring_len++;
+		}
+	}
+#endif
 	bdp->cbd_sc |= (BD_ENET_TX_READY | BD_ENET_TX_INTR
 			| BD_ENET_TX_LAST | BD_ENET_TX_TC);
 
@@ -408,8 +468,16 @@
 	} else {
 		bdp++;
 	}
+	fep->tx_ring_len++;
 
 	if (bdp->cbd_sc & BD_ENET_TX_READY)
+		fep->tx_full = 1;
+
+#ifdef CONFIG_FEC_SUPPORT_SG
+	if (fep->tx_ring_len + MAX_SKB_FRAGS >= TX_RING_SIZE)
+#else
+	if (fep->tx_ring_len >= TX_RING_SIZE)
+#endif
 		netif_stop_queue(dev);
 
 	fep->cur_tx = (cbd_t *)bdp;
@@ -541,53 +609,55 @@
 	while ((bdp->cbd_sc&BD_ENET_TX_READY) == 0) {
 		if (bdp == fep->cur_tx && fep->tx_full == 0) break;
 
-		skb = fep->tx_skbuff[fep->skb_dirty];
-		/* Check for errors. */
-		if (bdp->cbd_sc & (BD_ENET_TX_HB | BD_ENET_TX_LC |
-				   BD_ENET_TX_RL | BD_ENET_TX_UN |
-				   BD_ENET_TX_CSL)) {
-			fep->stats.tx_errors++;
-			if (bdp->cbd_sc & BD_ENET_TX_HB)  /* No heartbeat */
-				fep->stats.tx_heartbeat_errors++;
-			if (bdp->cbd_sc & BD_ENET_TX_LC)  /* Late collision */
-				fep->stats.tx_window_errors++;
-			if (bdp->cbd_sc & BD_ENET_TX_RL)  /* Retrans limit */
-				fep->stats.tx_aborted_errors++;
-			if (bdp->cbd_sc & BD_ENET_TX_UN)  /* Underrun */
-				fep->stats.tx_fifo_errors++;
-			if (bdp->cbd_sc & BD_ENET_TX_CSL) /* Carrier lost */
-				fep->stats.tx_carrier_errors++;
-		} else {
+		if (bdp->cbd_sc & BD_ENET_TX_LAST) {
+			/* Was last buffer of frame: check for errors
+			   and deal with skb. */
+
+			skb = fep->tx_skbuff[fep->skb_dirty];
+			/* Check for errors. */
+			if (bdp->cbd_sc & (BD_ENET_TX_HB | BD_ENET_TX_LC |
+					   BD_ENET_TX_RL | BD_ENET_TX_UN |
+					   BD_ENET_TX_CSL)) {
+				fep->stats.tx_errors++;
+				if (bdp->cbd_sc & BD_ENET_TX_HB)  /* No heartbeat */
+					fep->stats.tx_heartbeat_errors++;
+				if (bdp->cbd_sc & BD_ENET_TX_LC)  /* Late collision */
+					fep->stats.tx_window_errors++;
+				if (bdp->cbd_sc & BD_ENET_TX_RL)  /* Retrans limit */
+					fep->stats.tx_aborted_errors++;
+				if (bdp->cbd_sc & BD_ENET_TX_UN)  /* Underrun */
+					fep->stats.tx_fifo_errors++;
+				if (bdp->cbd_sc & BD_ENET_TX_CSL) /* Carrier lost */
+					fep->stats.tx_carrier_errors++;
+			} else {
 #ifdef CONFIG_FEC_PACKETHOOK
-			/* Packet hook ... */
-			if (fep->ph_txhandler &&
-			    ((struct ethhdr *)skb->data)->h_proto
-			    == fep->ph_proto) {
-				fep->ph_txhandler((__u8*)skb->data, skb->len,
-						  regval, fep->ph_priv);
-			}
+				/* Packet hook ... */
+				if (fep->ph_txhandler &&
+				    ((struct ethhdr *)skb->data)->h_proto
+				    == fep->ph_proto) {
+					fep->ph_txhandler((__u8*)skb->data, skb->len,
+							  regval, fep->ph_priv);
+				}
 #endif
-			fep->stats.tx_packets++;
-		}
+				fep->stats.tx_packets++;
+			}
 
-#ifndef final_version
-		if (bdp->cbd_sc & BD_ENET_TX_READY)
-			printk("HEY! Enet xmit interrupt and TX_READY.\n");
-#endif
-		/* Deferred means some collisions occurred during transmit,
-		 * but we eventually sent the packet OK.
-		 */
-		if (bdp->cbd_sc & BD_ENET_TX_DEF)
-			fep->stats.collisions++;
+			/* Deferred means some collisions occurred during transmit,
+			 * but we eventually sent the packet OK.
+			 */
+			if (bdp->cbd_sc & BD_ENET_TX_DEF)
+				fep->stats.collisions++;
 
-		/* Free the sk buffer associated with this last transmit.
-		 */
+			/* Free the sk buffer associated with this last transmit.
+			 */
 #if 0
 printk("TXI: %x %x %x\n", bdp, skb, fep->skb_dirty);
 #endif
-		dev_kfree_skb_irq (skb/*, FREE_WRITE*/);
-		fep->tx_skbuff[fep->skb_dirty] = NULL;
-		fep->skb_dirty = (fep->skb_dirty + 1) & TX_RING_MOD_MASK;
+			dev_kfree_skb_irq (skb/*, FREE_WRITE*/);
+			fep->tx_skbuff[fep->skb_dirty] = NULL;
+			fep->skb_dirty = (fep->skb_dirty + 1) & TX_RING_MOD_MASK;
+
+		}
 
 		/* Update pointer to next buffer descriptor to be transmitted.
 		 */
@@ -595,21 +665,26 @@
 			bdp = fep->tx_bd_base;
 		else
 			bdp++;
+		fep->tx_ring_len--;
 
-		/* Since we have freed up a buffer, the ring is no longer
-		 * full.
-		 */
-		if (fep->tx_full) {
-			fep->tx_full = 0;
-			if (netif_queue_stopped(dev))
-				netif_wake_queue(dev);
-		}
 #ifdef CONFIG_FEC_PACKETHOOK
 		/* Re-read register. Not exactly guaranteed to be correct,
 		   but... */
 		if (fep->ph_regaddr) regval = *fep->ph_regaddr;
 #endif
 	}
+
+	/* Wake queue if there is enough room in the tx ring */
+#ifdef CONFIG_FEC_SUPPORT_SG
+	if (fep->tx_full && fep->tx_ring_len + MAX_SKB_FRAGS < TX_RING_SIZE) {
+#else
+	if (fep->tx_full && fep->tx_ring_len < TX_RING_SIZE) {
+#endif
+		fep->tx_full = 0;
+		if (netif_queue_stopped(dev))
+			netif_wake_queue(dev);
+	}
+
 	fep->dirty_tx = (cbd_t *)bdp;
 	spin_unlock(&fep->lock);
 }
@@ -1852,8 +1927,10 @@
 
 	/* Enable interrupts we wish to service.
 	*/
+/* Joris: don't ask for TXB and RXB, we won't use them anyway.
 	fecp->fec_imask = ( FEC_ENET_TXF | FEC_ENET_TXB |
-			    FEC_ENET_RXF | FEC_ENET_RXB | FEC_ENET_MII );
+			    FEC_ENET_RXF | FEC_ENET_RXB | FEC_ENET_MII ); */
+	fecp->fec_imask = ( FEC_ENET_TXF | FEC_ENET_RXF | FEC_ENET_MII );
 
 	/* And last, enable the transmit and receive processing.
 	*/