net: bcmgenet: collect Rx discarded packet count

Bits 31:16 of RDMA_PROD_INDEX contain Rx discarded packet count, which
are the Rx packets that had to be dropped by MAC hardware since there
was no room on the Rx queue. Add code to collect this information into
the netdev stats.

Signed-off-by: Petri Gynther <pgynther@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 19 insertions, 0 deletions

diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
index 275be56fd324..d3be1aeb7f47 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -1384,9 +1384,27 @@ static unsigned int bcmgenet_desc_rx(struct bcmgenet_priv *priv,
         int len, err;
         unsigned int rxpktprocessed = 0, rxpkttoprocess;
         unsigned int p_index;
+        unsigned int discards;
         unsigned int chksum_ok = 0;
 
         p_index = bcmgenet_rdma_ring_readl(priv, index, RDMA_PROD_INDEX);
+
+        discards = (p_index >> DMA_P_INDEX_DISCARD_CNT_SHIFT) &
+                   DMA_P_INDEX_DISCARD_CNT_MASK;
+        if (discards > ring->old_discards) {
+                discards = discards - ring->old_discards;
+                dev->stats.rx_missed_errors += discards;
+                dev->stats.rx_errors += discards;
+                ring->old_discards += discards;
+
+                /* Clear HW register when we reach 75% of maximum 0xFFFF */
+                if (ring->old_discards >= 0xC000) {
+                        ring->old_discards = 0;
+                        bcmgenet_rdma_ring_writel(priv, index, 0,
+                                                  RDMA_PROD_INDEX);
+                }
+        }
+
         p_index &= DMA_P_INDEX_MASK;
 
         if (likely(p_index >= ring->c_index))
diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.h b/drivers/net/ethernet/broadcom/genet/bcmgenet.h
index 17443db8dc53..2a8113898aed 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.h
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.h
@@ -548,6 +548,7 @@ struct bcmgenet_rx_ring {
         unsigned int    read_ptr;       /* Rx ring read pointer */
         unsigned int    cb_ptr;         /* Rx ring initial CB ptr */
         unsigned int    end_ptr;        /* Rx ring end CB ptr */
+        unsigned int    old_discards;
 };
 
 /* device context */