[PATCH net-next 07/12] net: bcmgenet: clear status to reduce spurious interrupts

[Doug Berger]

Since the DMA interrupt status is latched and the DMA servicing can be
polled, it is a good idea to clear the latched status of a DMA interrupt
before performing the service that would be invoked by the interrupt.

This prevents old status from causing spurious interrupts when the
interrupt is unmasked at a later time.

Signed-off-by: Doug Berger <open...@gmail.com>
---
 drivers/net/ethernet/broadcom/genet/bcmgenet.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c 
b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
index 661ca1b39c89..1f94ba1773dd 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -1174,6 +1174,14 @@ static unsigned int __bcmgenet_tx_reclaim(struct 
net_device *dev,
        unsigned int txbds_ready;
        unsigned int txbds_processed = 0;
 
+       /* Clear status before servicing to reduce spurious interrupts */
+       if (ring->index == DESC_INDEX)
+               bcmgenet_intrl2_0_writel(priv, UMAC_IRQ_TXDMA_DONE,
+                                        INTRL2_CPU_CLEAR);
+       else
+               bcmgenet_intrl2_1_writel(priv, (1 << ring->index),
+                                        INTRL2_CPU_CLEAR);
+
        /* Compute how many buffers are transmitted since last xmit call */
        c_index = bcmgenet_tdma_ring_readl(priv, ring->index, TDMA_CONS_INDEX)
                & DMA_C_INDEX_MASK;
@@ -1584,10 +1592,21 @@ static unsigned int bcmgenet_desc_rx(struct 
bcmgenet_rx_ring *ring,
        unsigned long dma_flag;
        int len;
        unsigned int rxpktprocessed = 0, rxpkttoprocess;
-       unsigned int p_index;
+       unsigned int p_index, mask;
        unsigned int discards;
        unsigned int chksum_ok = 0;
 
+       /* Clear status before servicing to reduce spurious interrupts */
+       if (ring->index == DESC_INDEX) {
+               bcmgenet_intrl2_0_writel(priv, UMAC_IRQ_RXDMA_DONE,
+                                        INTRL2_CPU_CLEAR);
+       } else {
+               mask = 1 << (UMAC_IRQ1_RX_INTR_SHIFT + ring->index);
+               bcmgenet_intrl2_1_writel(priv,
+                                        mask,
+                                        INTRL2_CPU_CLEAR);
+       }
+
        p_index = bcmgenet_rdma_ring_readl(priv, ring->index, RDMA_PROD_INDEX);
 
        discards = (p_index >> DMA_P_INDEX_DISCARD_CNT_SHIFT) &
-- 
2.11.1