1 files changed, 99 insertions, 29 deletions

diff --git a/drivers/net/e100.c b/drivers/net/e100.c
index 597fd29..d87636d 100644
--- a/drivers/net/e100.c
+++ b/drivers/net/e100.c
@@ -106,6 +106,13 @@
  *	the RFD, the RFD must be dma_sync'ed to maintain a consistent
  *	view from software and hardware.
  *
+ *	In order to keep updates to the RFD link field from colliding with
+ *	hardware writes to mark packets complete, we use the feature that
+ *	hardware will not write to a size 0 descriptor and mark the previous
+ *	packet as end-of-list (EL).   After updating the link, we remove EL
+ *	and only then restore the size such that hardware may use the
+ *	previous-to-end RFD.
+ *
  *	Under typical operation, the  receive unit (RU) is start once,
  *	and the controller happily fills RFDs as frames arrive.  If
  *	replacement RFDs cannot be allocated, or the RU goes non-active,
@@ -281,6 +288,7 @@ struct csr {
 };
 
 enum scb_status {
+	rus_no_res       = 0x08,
 	rus_ready        = 0x10,
 	rus_mask         = 0x3C,
 };
@@ -952,7 +960,7 @@ static void e100_get_defaults(struct nic *nic)
 		((nic->mac >= mac_82558_D101_A4) ? cb_cid : cb_i));
 
 	/* Template for a freshly allocated RFD */
-	nic->blank_rfd.command = cpu_to_le16(cb_el);
+	nic->blank_rfd.command = 0;
 	nic->blank_rfd.rbd = 0xFFFFFFFF;
 	nic->blank_rfd.size = cpu_to_le16(VLAN_ETH_FRAME_LEN);
 
@@ -1791,15 +1799,12 @@ static int e100_rx_alloc_skb(struct nic *nic, struct rx *rx)
 	}
 
 	/* Link the RFD to end of RFA by linking previous RFD to
-	 * this one, and clearing EL bit of previous.  */
+	 * this one.  We are safe to touch the previous RFD because
+	 * it is protected by the before last buffer's el bit being set */
 	if(rx->prev->skb) {
 		struct rfd *prev_rfd = (struct rfd *)rx->prev->skb->data;
 		put_unaligned(cpu_to_le32(rx->dma_addr),
 			(u32 *)&prev_rfd->link);
-		wmb();
-		prev_rfd->command &= ~cpu_to_le16(cb_el);
-		pci_dma_sync_single_for_device(nic->pdev, rx->prev->dma_addr,
-			sizeof(struct rfd), PCI_DMA_TODEVICE);
 	}
 
 	return 0;
@@ -1824,8 +1829,19 @@ static int e100_rx_indicate(struct nic *nic, struct rx *rx,
 	DPRINTK(RX_STATUS, DEBUG, "status=0x%04X\n", rfd_status);
 
 	/* If data isn't ready, nothing to indicate */
-	if(unlikely(!(rfd_status & cb_complete)))
+	if (unlikely(!(rfd_status & cb_complete))) {
+		/* If the next buffer has the el bit, but we think the receiver
+		 * is still running, check to see if it really stopped while
+		 * we had interrupts off.
+		 * This allows for a fast restart without re-enabling
+		 * interrupts */
+		if ((le16_to_cpu(rfd->command) & cb_el) &&
+		    (RU_RUNNING == nic->ru_running))
+
+			if (readb(&nic->csr->scb.status) & rus_no_res)
+				nic->ru_running = RU_SUSPENDED;
 		return -ENODATA;
+	}
 
 	/* Get actual data size */
 	actual_size = le16_to_cpu(rfd->actual_size) & 0x3FFF;
@@ -1836,9 +1852,18 @@ static int e100_rx_indicate(struct nic *nic, struct rx *rx,
 	pci_unmap_single(nic->pdev, rx->dma_addr,
 		RFD_BUF_LEN, PCI_DMA_FROMDEVICE);
 
-	/* this allows for a fast restart without re-enabling interrupts */
-	if(le16_to_cpu(rfd->command) & cb_el)
+	/* If this buffer has the el bit, but we think the receiver
+	 * is still running, check to see if it really stopped while
+	 * we had interrupts off.
+	 * This allows for a fast restart without re-enabling interrupts.
+	 * This can happen when the RU sees the size change but also sees
+	 * the el bit set. */
+	if ((le16_to_cpu(rfd->command) & cb_el) &&
+	    (RU_RUNNING == nic->ru_running)) {
+
+	    if (readb(&nic->csr->scb.status) & rus_no_res)
 		nic->ru_running = RU_SUSPENDED;
+	}
 
 	/* Pull off the RFD and put the actual data (minus eth hdr) */
 	skb_reserve(skb, sizeof(struct rfd));
@@ -1870,31 +1895,30 @@ static void e100_rx_clean(struct nic *nic, unsigned int *work_done,
 	unsigned int work_to_do)
 {
 	struct rx *rx;
-	int restart_required = 0;
-	struct rx *rx_to_start = NULL;
-
-	/* are we already rnr? then pay attention!!! this ensures that
-	 * the state machine progression never allows a start with a
-	 * partially cleaned list, avoiding a race between hardware
-	 * and rx_to_clean when in NAPI mode */
-	if(RU_SUSPENDED == nic->ru_running)
-		restart_required = 1;
+	int restart_required = 0, err = 0;
+	struct rx *old_before_last_rx, *new_before_last_rx;
+	struct rfd *old_before_last_rfd, *new_before_last_rfd;
 
 	/* Indicate newly arrived packets */
 	for(rx = nic->rx_to_clean; rx->skb; rx = nic->rx_to_clean = rx->next) {
-		int err = e100_rx_indicate(nic, rx, work_done, work_to_do);
-		if(-EAGAIN == err) {
-			/* hit quota so have more work to do, restart once
-			 * cleanup is complete */
-			restart_required = 0;
+		err = e100_rx_indicate(nic, rx, work_done, work_to_do);
+		/* Hit quota or no more to clean */
+		if (-EAGAIN == err || -ENODATA == err)
 			break;
-		} else if(-ENODATA == err)
-			break; /* No more to clean */
 	}
 
-	/* save our starting point as the place we'll restart the receiver */
-	if(restart_required)
-		rx_to_start = nic->rx_to_clean;
+
+	/* On EAGAIN, hit quota so have more work to do, restart once
+	 * cleanup is complete.
+	 * Else, are we already rnr? then pay attention!!! this ensures that
+	 * the state machine progression never allows a start with a
+	 * partially cleaned list, avoiding a race between hardware
+	 * and rx_to_clean when in NAPI mode */
+	if (-EAGAIN != err && RU_SUSPENDED == nic->ru_running)
+		restart_required = 1;
+
+	old_before_last_rx = nic->rx_to_use->prev->prev;
+	old_before_last_rfd = (struct rfd *)old_before_last_rx->skb->data;
 
 	/* Alloc new skbs to refill list */
 	for(rx = nic->rx_to_use; !rx->skb; rx = nic->rx_to_use = rx->next) {
@@ -1902,10 +1926,42 @@ static void e100_rx_clean(struct nic *nic, unsigned int *work_done,
 			break; /* Better luck next time (see watchdog) */
 	}
 
+	new_before_last_rx = nic->rx_to_use->prev->prev;
+	if (new_before_last_rx != old_before_last_rx) {
+		/* Set the el-bit on the buffer that is before the last buffer.
+		 * This lets us update the next pointer on the last buffer
+		 * without worrying about hardware touching it.
+		 * We set the size to 0 to prevent hardware from touching this
+		 * buffer.
+		 * When the hardware hits the before last buffer with el-bit
+		 * and size of 0, it will RNR interrupt, the RUS will go into
+		 * the No Resources state.  It will not complete nor write to
+		 * this buffer. */
+		new_before_last_rfd =
+			(struct rfd *)new_before_last_rx->skb->data;
+		new_before_last_rfd->size = 0;
+		new_before_last_rfd->command |= cpu_to_le16(cb_el);
+		pci_dma_sync_single_for_device(nic->pdev,
+			new_before_last_rx->dma_addr, sizeof(struct rfd),
+			PCI_DMA_TODEVICE);
+
+		/* Now that we have a new stopping point, we can clear the old
+		 * stopping point.  We must sync twice to get the proper
+		 * ordering on the hardware side of things. */
+		old_before_last_rfd->command &= ~cpu_to_le16(cb_el);
+		pci_dma_sync_single_for_device(nic->pdev,
+			old_before_last_rx->dma_addr, sizeof(struct rfd),
+			PCI_DMA_TODEVICE);
+		old_before_last_rfd->size = cpu_to_le16(VLAN_ETH_FRAME_LEN);
+		pci_dma_sync_single_for_device(nic->pdev,
+			old_before_last_rx->dma_addr, sizeof(struct rfd),
+			PCI_DMA_TODEVICE);
+	}
+
 	if(restart_required) {
 		// ack the rnr?
 		writeb(stat_ack_rnr, &nic->csr->scb.stat_ack);
-		e100_start_receiver(nic, rx_to_start);
+		e100_start_receiver(nic, nic->rx_to_clean);
 		if(work_done)
 			(*work_done)++;
 	}
@@ -1937,6 +1993,7 @@ static int e100_rx_alloc_list(struct nic *nic)
 {
 	struct rx *rx;
 	unsigned int i, count = nic->params.rfds.count;
+	struct rfd *before_last;
 
 	nic->rx_to_use = nic->rx_to_clean = NULL;
 	nic->ru_running = RU_UNINITIALIZED;
@@ -1952,6 +2009,19 @@ static int e100_rx_alloc_list(struct nic *nic)
 			return -ENOMEM;
 		}
 	}
+	/* Set the el-bit on the buffer that is before the last buffer.
+	 * This lets us update the next pointer on the last buffer without
+	 * worrying about hardware touching it.
+	 * We set the size to 0 to prevent hardware from touching this buffer.
+	 * When the hardware hits the before last buffer with el-bit and size
+	 * of 0, it will RNR interrupt, the RU will go into the No Resources
+	 * state.  It will not complete nor write to this buffer. */
+	rx = nic->rxs->prev->prev;
+	before_last = (struct rfd *)rx->skb->data;
+	before_last->command |= cpu_to_le16(cb_el);
+	before_last->size = 0;
+	pci_dma_sync_single_for_device(nic->pdev, rx->dma_addr,
+		sizeof(struct rfd), PCI_DMA_TODEVICE);
 
 	nic->rx_to_use = nic->rx_to_clean = nic->rxs;
 	nic->ru_running = RU_SUSPENDED;