net: systemport: Clear status to reduce spurious interrupts

Do something similar to commit d5810ca3 ("net: bcmgenet: clear
status to reduce spurious interrupts") and clear interrupts right before
servicing them. This reduces the number of interrupts by 10K
interrupts/sec for a TX TCP session 1Gbits/sec.
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bcmsysport.c

@@ -669,6 +669,9 @@ static unsigned int bcm_sysport_desc_rx(struct bcm_sysport_priv *priv,
 	u16 len, status;
 	struct bcm_rsb *rsb;
 
+	/* Clear status before servicing to reduce spurious interrupts */
+	intrl2_0_writel(priv, INTRL2_0_RDMA_MBDONE, INTRL2_CPU_CLEAR);
+
 	/* Determine how much we should process since last call, SYSTEMPORT Lite
 	 * groups the producer and consumer indexes into the same 32-bit
 	 * which we access using RDMA_CONS_INDEX
@@ -814,6 +817,13 @@ static unsigned int __bcm_sysport_tx_reclaim(struct bcm_sysport_priv *priv,
 	struct bcm_sysport_cb *cb;
 	u32 hw_ind;
 
+	/* Clear status before servicing to reduce spurious interrupts */
+	if (!ring->priv->is_lite)
+		intrl2_1_writel(ring->priv, BIT(ring->index), INTRL2_CPU_CLEAR);
+	else
+		intrl2_0_writel(ring->priv, BIT(ring->index +
+				INTRL2_0_TDMA_MBDONE_SHIFT), INTRL2_CPU_CLEAR);
+
 	/* Compute how many descriptors have been processed since last call */
 	hw_ind = tdma_readl(priv, TDMA_DESC_RING_PROD_CONS_INDEX(ring->index));
 	c_index = (hw_ind >> RING_CONS_INDEX_SHIFT) & RING_CONS_INDEX_MASK;