Revert "[netdrvr e100] experiment with doing RX in a similar manner to eepro100"

This reverts commit d52df4a3.

This patch attempted to fix e100 for non-cache coherent memory
architectures by using the cb style code that eepro100 had and using
the EL and s bits from the RFD list. Unfortunately the hardware
doesn't work exactly like this and therefore this patch actually
breaks e100. Reverting the change brings it back to the previously
known good state for 2.6.22. The pending rewrite in progress to this
code can then be safely merged later.
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/e100.c

@@ -285,6 +285,12 @@ enum scb_status {
 	rus_mask         = 0x3C,
 };
 
+enum ru_state  {
+	RU_SUSPENDED = 0,
+	RU_RUNNING	 = 1,
+	RU_UNINITIALIZED = -1,
+};
+
 enum scb_stat_ack {
 	stat_ack_not_ours    = 0x00,
 	stat_ack_sw_gen      = 0x04,
@@ -526,6 +532,7 @@ struct nic {
 	struct rx *rx_to_use;
 	struct rx *rx_to_clean;
 	struct rfd blank_rfd;
+	enum ru_state ru_running;
 
 	spinlock_t cb_lock			____cacheline_aligned;
 	spinlock_t cmd_lock;
@@ -947,7 +954,7 @@ 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 & cb_s);
+	nic->blank_rfd.command = cpu_to_le16(cb_el);
 	nic->blank_rfd.rbd = 0xFFFFFFFF;
 	nic->blank_rfd.size = cpu_to_le16(VLAN_ETH_FRAME_LEN);
 
@@ -1742,11 +1749,19 @@ static int e100_alloc_cbs(struct nic *nic)
 	return 0;
 }
 
-static inline void e100_start_receiver(struct nic *nic)
+static inline void e100_start_receiver(struct nic *nic, struct rx *rx)
 {
-	/* Start if RFA is non-NULL */
-	if(nic->rx_to_clean->skb)
-		e100_exec_cmd(nic, ruc_start, nic->rx_to_clean->dma_addr);
+	if(!nic->rxs) return;
+	if(RU_SUSPENDED != nic->ru_running) return;
+
+	/* handle init time starts */
+	if(!rx) rx = nic->rxs;
+
+	/* (Re)start RU if suspended or idle and RFA is non-NULL */
+	if(rx->skb) {
+		e100_exec_cmd(nic, ruc_start, rx->dma_addr);
+		nic->ru_running = RU_RUNNING;
+	}
 }
 
 #define RFD_BUF_LEN (sizeof(struct rfd) + VLAN_ETH_FRAME_LEN)
@@ -1775,7 +1790,7 @@ static int e100_rx_alloc_skb(struct nic *nic, struct rx *rx)
 		put_unaligned(cpu_to_le32(rx->dma_addr),
 			(u32 *)&prev_rfd->link);
 		wmb();
-		prev_rfd->command &= ~cpu_to_le16(cb_el & cb_s);
+		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);
 	}
@@ -1813,6 +1828,10 @@ 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)
+		nic->ru_running = RU_SUSPENDED;
+
 	/* Pull off the RFD and put the actual data (minus eth hdr) */
 	skb_reserve(skb, sizeof(struct rfd));
 	skb_put(skb, actual_size);
@@ -1843,18 +1862,45 @@ 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;
 
 	/* Indicate newly arrived packets */
 	for(rx = nic->rx_to_clean; rx->skb; rx = nic->rx_to_clean = rx->next) {
-		if(e100_rx_indicate(nic, rx, work_done, work_to_do))
+		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;
+			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;
+
 	/* Alloc new skbs to refill list */
 	for(rx = nic->rx_to_use; !rx->skb; rx = nic->rx_to_use = rx->next) {
 		if(unlikely(e100_rx_alloc_skb(nic, rx)))
 			break; /* Better luck next time (see watchdog) */
 	}
+
+	if(restart_required) {
+		// ack the rnr?
+		writeb(stat_ack_rnr, &nic->csr->scb.stat_ack);
+		e100_start_receiver(nic, rx_to_start);
+		if(work_done)
+			(*work_done)++;
+	}
 }
 
 static void e100_rx_clean_list(struct nic *nic)
@@ -1862,6 +1908,8 @@ static void e100_rx_clean_list(struct nic *nic)
 	struct rx *rx;
 	unsigned int i, count = nic->params.rfds.count;
 
+	nic->ru_running = RU_UNINITIALIZED;
+
 	if(nic->rxs) {
 		for(rx = nic->rxs, i = 0; i < count; rx++, i++) {
 			if(rx->skb) {
@@ -1883,6 +1931,7 @@ static int e100_rx_alloc_list(struct nic *nic)
 	unsigned int i, count = nic->params.rfds.count;
 
 	nic->rx_to_use = nic->rx_to_clean = NULL;
+	nic->ru_running = RU_UNINITIALIZED;
 
 	if(!(nic->rxs = kcalloc(count, sizeof(struct rx), GFP_ATOMIC)))
 		return -ENOMEM;
@@ -1897,6 +1946,7 @@ static int e100_rx_alloc_list(struct nic *nic)
 	}
 
 	nic->rx_to_use = nic->rx_to_clean = nic->rxs;
+	nic->ru_running = RU_SUSPENDED;
 
 	return 0;
 }
@@ -1916,6 +1966,10 @@ static irqreturn_t e100_intr(int irq, void *dev_id)
 	/* Ack interrupt(s) */
 	iowrite8(stat_ack, &nic->csr->scb.stat_ack);
 
+	/* We hit Receive No Resource (RNR); restart RU after cleaning */
+	if(stat_ack & stat_ack_rnr)
+		nic->ru_running = RU_SUSPENDED;
+
 	if(likely(netif_rx_schedule_prep(netdev))) {
 		e100_disable_irq(nic);
 		__netif_rx_schedule(netdev);
@@ -2007,7 +2061,7 @@ static int e100_up(struct nic *nic)
 	if((err = e100_hw_init(nic)))
 		goto err_clean_cbs;
 	e100_set_multicast_list(nic->netdev);
-	e100_start_receiver(nic);
+	e100_start_receiver(nic, NULL);
 	mod_timer(&nic->watchdog, jiffies);
 	if((err = request_irq(nic->pdev->irq, e100_intr, IRQF_SHARED,
 		nic->netdev->name, nic->netdev)))
@@ -2088,7 +2142,7 @@ static int e100_loopback_test(struct nic *nic, enum loopback loopback_mode)
 		mdio_write(nic->netdev, nic->mii.phy_id, MII_BMCR,
 			BMCR_LOOPBACK);
 
-	e100_start_receiver(nic);
+	e100_start_receiver(nic, NULL);
 
 	if(!(skb = netdev_alloc_skb(nic->netdev, ETH_DATA_LEN))) {
 		err = -ENOMEM;