[PATCH v2 3/5] net: ethernet: cortina: Count dropped frames as NAPI work

[Linus Walleij <linusw@kernel.org>]

The RX loop only consumes budget when it successfully delivers a frame.
Error paths keep consuming descriptors without reducing the budget, so a
stream of bad frames can process the entire receive ring in one poll.

Move the budget accounting to a common end-of-frame path. This counts
each completed frame as NAPI work whether it was delivered or dropped,
matching the behavior of the vendor driver.

Fixes: 4d5ae32f5e1e ("net: ethernet: Add a driver for Gemini gigabit ethernet")
Assisted-by: LLM
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/net/ethernet/cortina/gemini.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/cortina/gemini.c b/drivers/net/ethernet/cortina/gemini.c
index 6502220362cb..33e9763b32fe 100644
--- a/drivers/net/ethernet/cortina/gemini.c
+++ b/drivers/net/ethernet/cortina/gemini.c
@@ -1501,7 +1501,7 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 				skb = NULL;
 				frag_nr = 0;
 			}
-			continue;
+			goto next_desc;
 		}
 		page = gpage->page;
 
@@ -1523,7 +1523,7 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 
 		} else if (!skb) {
 			put_page(page);
-			continue;
+			goto next_desc;
 		}
 
 		if (word3.bits32 & EOF_BIT)
@@ -1546,10 +1546,8 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 			napi_gro_frags(&port->napi);
 			skb = NULL;
 			frag_nr = 0;
-			budget--;
-			received++;
 		}
-		continue;
+		goto next_desc;
 
 err_drop:
 		if (skb) {
@@ -1562,6 +1560,13 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 			put_page(page);
 
 		port->stats.rx_dropped++;
+
+next_desc:
+		/* Final or single-descriptor fragment, advance things */
+		if (word3.bits32 & EOF_BIT) {
+			budget--;
+			received++;
+		}
 	}
 
 	port->rx_skb = skb;

-- 
2.55.0