chelsio: NAPI speed improvement

Speedup and cleanup the receive processing by eliminating the
mmio read and a lock round trip.

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

1 files changed, 35 insertions, 42 deletions

diff --git a/drivers/net/chelsio/sge.c b/drivers/net/chelsio/sge.c
index f94d63971642..8e287e79e4e3 100644
--- a/drivers/net/chelsio/sge.c
+++ b/drivers/net/chelsio/sge.c
@@ -1559,6 +1559,14 @@ static int process_responses(struct adapter *adapter, int budget)
         return budget;
 }
 
+static inline int responses_pending(const struct adapter *adapter)
+{
+        const struct respQ *Q = &adapter->sge->respQ;
+        const struct respQ_e *e = &Q->entries[Q->cidx];
+
+        return (e->GenerationBit == Q->genbit);
+}
+
 #ifdef CONFIG_CHELSIO_T1_NAPI
 /*
  * A simpler version of process_responses() that handles only pure (i.e.,
@@ -1568,13 +1576,16 @@ static int process_responses(struct adapter *adapter, int budget)
  * which the caller must ensure is a valid pure response.  Returns 1 if it
  * encounters a valid data-carrying response, 0 otherwise.
  */
-static int process_pure_responses(struct adapter *adapter, struct respQ_e *e)
+static int process_pure_responses(struct adapter *adapter)
 {
         struct sge *sge = adapter->sge;
         struct respQ *q = &sge->respQ;
+        struct respQ_e *e = &q->entries[q->cidx];
         unsigned int flags = 0;
         unsigned int cmdq_processed[SGE_CMDQ_N] = {0, 0};
 
+        if (e->DataValid)
+                return 1;
         do {
                 flags |= e->Qsleeping;
 
@@ -1610,23 +1621,20 @@ static int process_pure_responses(struct adapter *adapter, struct respQ_e *e)
 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);
+        int work_done;
 
+        work_done = process_responses(adapter, min(*budget, dev->quota));
         *budget -= work_done;
         dev->quota -= work_done;
 
-        if (work_done >= effective_budget)
+        if (unlikely(responses_pending(adapter)))
                 return 1;
 
-        spin_lock_irq(&adapter->async_lock);
-        __netif_rx_complete(dev);
+        netif_rx_complete(dev);
         writel(adapter->sge->respQ.cidx, adapter->regs + A_SG_SLEEPING);
-        writel(adapter->slow_intr_mask | F_PL_INTR_SGE_DATA,
-               adapter->regs + A_PL_ENABLE);
-        spin_unlock_irq(&adapter->async_lock);
 
         return 0;
+
 }
 
 /*
@@ -1635,44 +1643,33 @@ int t1_poll(struct net_device *dev, int *budget)
 irqreturn_t t1_interrupt(int irq, void *data)
 {
         struct adapter *adapter = data;
-        struct net_device *dev = adapter->sge->netdev;
         struct sge *sge = adapter->sge;
-        u32 cause;
-        int handled = 0;
-
-        cause = readl(adapter->regs + A_PL_CAUSE);
-        if (cause == 0 || cause == ~0)
-                return IRQ_NONE;
+        int handled;
 
-        spin_lock(&adapter->async_lock);
-        if (cause & F_PL_INTR_SGE_DATA) {
-                struct respQ *q = &adapter->sge->respQ;
-                struct respQ_e *e = &q->entries[q->cidx];
+        if (likely(responses_pending(adapter))) {
+                struct net_device *dev = sge->netdev;
 
-                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;
+                if (__netif_rx_schedule_prep(dev)) {
+                        if (process_pure_responses(adapter))
+                                __netif_rx_schedule(dev);
+                        else {
+                                /* no data, no NAPI needed */
+                                writel(sge->respQ.cidx, adapter->regs + A_SG_SLEEPING);
+                                netif_poll_enable(dev); /* undo schedule_prep */
                         }
-                        /* no data, no NAPI needed */
-                        netif_poll_enable(dev);
-
                 }
-                writel(q->cidx, adapter->regs + A_SG_SLEEPING);
-        } else
-                handled = t1_slow_intr_handler(adapter);
+                return IRQ_HANDLED;
+        }
+
+        spin_lock(&adapter->async_lock);
+        handled = t1_slow_intr_handler(adapter);
+        spin_unlock(&adapter->async_lock);
 
         if (!handled)
                 sge->stats.unhandled_irqs++;
-unlock:
-        spin_unlock(&adapter->async_lock);
+
         return IRQ_RETVAL(handled != 0);
 }
 
@@ -1695,17 +1692,13 @@ unlock:
 irqreturn_t t1_interrupt(int irq, void *cookie)
 {
         int work_done;
-        struct respQ_e *e;
         struct adapter *adapter = cookie;
-        struct respQ *Q = &adapter->sge->respQ;
 
         spin_lock(&adapter->async_lock);
-        e = &Q->entries[Q->cidx];
-        prefetch(e);
 
         writel(F_PL_INTR_SGE_DATA, adapter->regs + A_PL_CAUSE);
 
-        if (likely(e->GenerationBit == Q->genbit))
+        if (likely(responses_pending(adapter))
                 work_done = process_responses(adapter, -1);
         else
                 work_done = t1_slow_intr_handler(adapter);