[PATCH] chelsio: working NAPI

This driver tries to enable/disable NAPI at runtime, but
does so in an unsafe manner, and the NAPI interrupt handling is
a mess. Replace it with a compile time selected NAPI implementation.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

4 files changed, 67 insertions, 83 deletions

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 9de0eed6755b..8aa8dd02b910 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -2384,6 +2384,14 @@ config CHELSIO_T1_1G
           Enables support for Chelsio's gigabit Ethernet PCI cards.  If you
           are using only 10G cards say 'N' here.
 
+config CHELSIO_T1_NAPI
+        bool "Use Rx Polling (NAPI)"
+        depends on CHELSIO_T1
+        default y
+        help
+          NAPI is a driver API designed to reduce CPU and interrupt load
+          when the driver is receiving lots of packets from the card.
+
 config EHEA
         tristate "eHEA Ethernet support"
         depends on IBMEBUS
diff --git a/drivers/net/chelsio/cxgb2.c b/drivers/net/chelsio/cxgb2.c
index de48eadddbc4..fd5d821f3f2a 100644
--- a/drivers/net/chelsio/cxgb2.c
+++ b/drivers/net/chelsio/cxgb2.c
@@ -220,9 +220,8 @@ static int cxgb_up(struct adapter *adapter)
 
         t1_interrupts_clear(adapter);
 
-        adapter->params.has_msi = !disable_msi && pci_enable_msi(adapter->pdev) == 0;
-        err = request_irq(adapter->pdev->irq,
-                          t1_select_intr_handler(adapter),
+        adapter->params.has_msi = !disable_msi && !pci_enable_msi(adapter->pdev);
+        err = request_irq(adapter->pdev->irq, t1_interrupt,
                           adapter->params.has_msi ? 0 : IRQF_SHARED,
                           adapter->name, adapter);
         if (err) {
@@ -764,18 +763,7 @@ static int set_coalesce(struct net_device *dev, struct ethtool_coalesce *c)
 {
         struct adapter *adapter = dev->priv;
 
-        /*
-         * If RX coalescing is requested we use NAPI, otherwise interrupts.
-         * This choice can be made only when all ports and the TOE are off.
-         */
-        if (adapter->open_device_map == 0)
-                adapter->params.sge.polling = c->use_adaptive_rx_coalesce;
-
-        if (adapter->params.sge.polling) {
-                adapter->params.sge.rx_coalesce_usecs = 0;
-        } else {
-                adapter->params.sge.rx_coalesce_usecs = c->rx_coalesce_usecs;
-        }
+        adapter->params.sge.rx_coalesce_usecs = c->rx_coalesce_usecs;
         adapter->params.sge.coalesce_enable = c->use_adaptive_rx_coalesce;
         adapter->params.sge.sample_interval_usecs = c->rate_sample_interval;
         t1_sge_set_coalesce_params(adapter->sge, &adapter->params.sge);
@@ -944,7 +932,7 @@ static void t1_netpoll(struct net_device *dev)
         struct adapter *adapter = dev->priv;
 
         local_irq_save(flags);
-        t1_select_intr_handler(adapter)(adapter->pdev->irq, adapter);
+        t1_interrupt(adapter->pdev->irq, adapter);
         local_irq_restore(flags);
 }
 #endif
@@ -1165,7 +1153,10 @@ static int __devinit init_one(struct pci_dev *pdev,
 #ifdef CONFIG_NET_POLL_CONTROLLER
                 netdev->poll_controller = t1_netpoll;
 #endif
+#ifdef CONFIG_CHELSIO_T1_NAPI
                 netdev->weight = 64;
+                netdev->poll = t1_poll;
+#endif
 
                 SET_ETHTOOL_OPS(netdev, &t1_ethtool_ops);
         }
diff --git a/drivers/net/chelsio/sge.c b/drivers/net/chelsio/sge.c
index 0ca8d876e16f..659cb2252e44 100644
--- a/drivers/net/chelsio/sge.c
+++ b/drivers/net/chelsio/sge.c
@@ -1413,16 +1413,20 @@ static int sge_rx(struct sge *sge, struct freelQ *fl, unsigned int len)
 
         if (unlikely(adapter->vlan_grp && p->vlan_valid)) {
                 st->vlan_xtract++;
-                if (adapter->params.sge.polling)
+#ifdef CONFIG_CHELSIO_T1_NAPI
                         vlan_hwaccel_receive_skb(skb, adapter->vlan_grp,
                                                  ntohs(p->vlan));
-                else
+#else
                         vlan_hwaccel_rx(skb, adapter->vlan_grp,
                                         ntohs(p->vlan));
-        } else if (adapter->params.sge.polling)
+#endif
+        } else {
+#ifdef CONFIG_CHELSIO_T1_NAPI
                 netif_receive_skb(skb);
-        else
+#else
                 netif_rx(skb);
+#endif
+        }
         return 0;
 }
 
@@ -1572,6 +1576,7 @@ static int process_responses(struct adapter *adapter, int budget)
         return budget;
 }
 
+#ifdef CONFIG_CHELSIO_T1_NAPI
 /*
  * A simpler version of process_responses() that handles only pure (i.e.,
  * non data-carrying) responses.  Such respones are too light-weight to justify
@@ -1619,92 +1624,76 @@ static int process_pure_responses(struct adapter *adapter, struct respQ_e *e)
  * or protection from interrupts as data interrupts are off at this point and
  * other adapter interrupts do not interfere.
  */
-static int t1_poll(struct net_device *dev, int *budget)
+int t1_poll(struct net_device *dev, int *budget)
 {
         struct adapter *adapter = dev->priv;
         int effective_budget = min(*budget, dev->quota);
-
         int work_done = process_responses(adapter, effective_budget);
+
         *budget -= work_done;
         dev->quota -= work_done;
 
         if (work_done >= effective_budget)
                 return 1;
 
+        spin_lock_irq(&adapter->async_lock);
         __netif_rx_complete(dev);
-
-        /*
-         * Because we don't atomically flush the following write it is
-         * possible that in very rare cases it can reach the device in a way
-         * that races with a new response being written plus an error interrupt
-         * causing the NAPI interrupt handler below to return unhandled status
-         * to the OS.  To protect against this would require flushing the write
-         * and doing both the write and the flush with interrupts off.  Way too
-         * expensive and unjustifiable given the rarity of the race.
-         */
         writel(adapter->sge->respQ.cidx, adapter->regs + A_SG_SLEEPING);
-        return 0;
-}
+        writel(adapter->slow_intr_mask | F_PL_INTR_SGE_DATA,
+               adapter->regs + A_PL_ENABLE);
+        spin_unlock_irq(&adapter->async_lock);
 
-/*
- * Returns true if the device is already scheduled for polling.
- */
-static inline int napi_is_scheduled(struct net_device *dev)
-{
-        return test_bit(__LINK_STATE_RX_SCHED, &dev->state);
+        return 0;
 }
 
 /*
  * NAPI version of the main interrupt handler.
  */
-static irqreturn_t t1_interrupt_napi(int irq, void *data)
+irqreturn_t t1_interrupt(int irq, void *data)
 {
-        int handled;
         struct adapter *adapter = data;
+        struct net_device *dev = adapter->sge->netdev;
         struct sge *sge = adapter->sge;
-        struct respQ *q = &adapter->sge->respQ;
+        u32 cause;
+        int handled = 0;
 
-        /*
-         * Clear the SGE_DATA interrupt first thing.  Normally the NAPI
-         * handler has control of the response queue and the interrupt handler
-         * can look at the queue reliably only once it knows NAPI is off.
-         * We can't wait that long to clear the SGE_DATA interrupt because we
-         * could race with t1_poll rearming the SGE interrupt, so we need to
-         * clear the interrupt speculatively and really early on.
-         */
-        writel(F_PL_INTR_SGE_DATA, adapter->regs + A_PL_CAUSE);
+        cause = readl(adapter->regs + A_PL_CAUSE);
+        if (cause == 0 || cause == ~0)
+                return IRQ_NONE;
 
         spin_lock(&adapter->async_lock);
-        if (!napi_is_scheduled(sge->netdev)) {
+        if (cause & F_PL_INTR_SGE_DATA) {
+                struct respQ *q = &adapter->sge->respQ;
                 struct respQ_e *e = &q->entries[q->cidx];
 
-                if (e->GenerationBit == q->genbit) {
-                        if (e->DataValid ||
-                            process_pure_responses(adapter, e)) {
-                                if (likely(__netif_rx_schedule_prep(sge->netdev)))
-                                        __netif_rx_schedule(sge->netdev);
-                                else if (net_ratelimit())
-                                        printk(KERN_INFO
-                                               "NAPI schedule failure!\n");
-                        } else
-                                writel(q->cidx, adapter->regs + A_SG_SLEEPING);
-
-                        handled = 1;
-                        goto unlock;
-                } else
-                        writel(q->cidx, adapter->regs + A_SG_SLEEPING);
-        }  else if (readl(adapter->regs + A_PL_CAUSE) & F_PL_INTR_SGE_DATA) {
-                printk(KERN_ERR "data interrupt while NAPI running\n");
-        }
-        
-        handled = t1_slow_intr_handler(adapter);
+                handled = 1;
+                writel(F_PL_INTR_SGE_DATA, adapter->regs + A_PL_CAUSE);
+
+                if (e->GenerationBit == q->genbit &&
+                    __netif_rx_schedule_prep(dev)) {
+                        if (e->DataValid || process_pure_responses(adapter, e)) {
+                                /* mask off data IRQ */
+                                writel(adapter->slow_intr_mask,
+                                       adapter->regs + A_PL_ENABLE);
+                                __netif_rx_schedule(sge->netdev);
+                                goto unlock;
+                        }
+                        /* no data, no NAPI needed */
+                        netif_poll_enable(dev);
+
+                }
+                writel(q->cidx, adapter->regs + A_SG_SLEEPING);
+        } else
+                handled = t1_slow_intr_handler(adapter);
+
         if (!handled)
                 sge->stats.unhandled_irqs++;
- unlock:
+unlock:
         spin_unlock(&adapter->async_lock);
         return IRQ_RETVAL(handled != 0);
 }
 
+#else
 /*
  * Main interrupt handler, optimized assuming that we took a 'DATA'
  * interrupt.
@@ -1720,7 +1709,7 @@ static irqreturn_t t1_interrupt_napi(int irq, void *data)
  * 5. If we took an interrupt, but no valid respQ descriptors was found we
  *      let the slow_intr_handler run and do error handling.
  */
-static irqreturn_t t1_interrupt(int irq, void *cookie)
+irqreturn_t t1_interrupt(int irq, void *cookie)
 {
         int work_done;
         struct respQ_e *e;
@@ -1752,11 +1741,7 @@ static irqreturn_t t1_interrupt(int irq, void *cookie)
         spin_unlock(&adapter->async_lock);
         return IRQ_RETVAL(work_done != 0);
 }
-
-irq_handler_t t1_select_intr_handler(adapter_t *adapter)
-{
-        return adapter->params.sge.polling ? t1_interrupt_napi : t1_interrupt;
-}
+#endif
 
 /*
  * Enqueues the sk_buff onto the cmdQ[qid] and has hardware fetch it.
@@ -2033,7 +2018,6 @@ static void sge_tx_reclaim_cb(unsigned long data)
  */
 int t1_sge_set_coalesce_params(struct sge *sge, struct sge_params *p)
 {
-        sge->netdev->poll = t1_poll;
         sge->fixed_intrtimer = p->rx_coalesce_usecs *
                 core_ticks_per_usec(sge->adapter);
         writel(sge->fixed_intrtimer, sge->adapter->regs + A_SG_INTRTIMER);
@@ -2234,7 +2218,6 @@ struct sge * __devinit t1_sge_create(struct adapter *adapter,
 
         p->coalesce_enable = 0;
         p->sample_interval_usecs = 0;
-        p->polling = 0;
 
         return sge;
 nomem_port:
diff --git a/drivers/net/chelsio/sge.h b/drivers/net/chelsio/sge.h
index 7ceb0117d039..d132a0ef2a22 100644
--- a/drivers/net/chelsio/sge.h
+++ b/drivers/net/chelsio/sge.h
@@ -76,7 +76,9 @@ struct sge *t1_sge_create(struct adapter *, struct sge_params *);
 int t1_sge_configure(struct sge *, struct sge_params *);
 int t1_sge_set_coalesce_params(struct sge *, struct sge_params *);
 void t1_sge_destroy(struct sge *);
-irq_handler_t t1_select_intr_handler(adapter_t *adapter);
+irqreturn_t t1_interrupt(int irq, void *cookie);
+int t1_poll(struct net_device *, int *);
+
 int t1_start_xmit(struct sk_buff *skb, struct net_device *dev);
 void t1_set_vlan_accel(struct adapter *adapter, int on_off);
 void t1_sge_start(struct sge *);