[PATCH v2 0/5] net: ethernet: cortina: Fix RX budget accounting

[PATCH v2 0/5] net: ethernet: cortina: Fix RX budget accounting

[Linus Walleij]

Finish RX updates before releasing NAPI ownership, report actual NAPI
work, charge dropped frames to the poll budget, and drive free-queue
refills from consumed RX descriptors.

Track RX drop state across descriptor chains so discarded frames are
counted exactly once.

Tested on the D-Link DIR-685.

Hi Sashiko, yes there are more latent issues I will get to them, but
my LLM thinks those are on the top of the list.

Assisted-by: LLM
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
Changes in v2:
- Finish RX statistics and free-queue updates before NAPI completion.
- Enable RX interrupts only after successful NAPI completion.
- Drop AI slop renaming of received->work_done.
- Link to v1: https://patch.msgid.link/20260901-gemini-ethernet-fixes-v1-0-ee6b09675876@kernel.org

---
Linus Walleij (5):
      net: ethernet: cortina: Fix budget accounting
      net: ethernet: cortina: Finish RX updates before NAPI completion
      net: ethernet: cortina: Count dropped frames as NAPI work
      net: ethernet: cortina: Count RX drops once per frame
      net: ethernet: cortina: Count RX descriptors for freeq refill

 drivers/net/ethernet/cortina/gemini.c | 77 +++++++++++++++++++++--------------
 1 file changed, 47 insertions(+), 30 deletions(-)
---
base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
change-id: 20260901-gemini-ethernet-fixes-e6d2e7c53c1b

Best regards,
--  
Linus Walleij <linusw@kernel.org>

[PATCH v2 1/5] net: ethernet: cortina: Fix budget accounting

[Linus Walleij]

The gmac_rx() function returns the remaining NAPI budget, but its
caller treats the return value as the number of packets received. An
idle poll therefore reports a full budget and remains scheduled.

Return the number of received packets instead. Preserve the existing
free queue refill accounting by adding that count directly; continuing
to subtract it from the budget would invert the refill behavior.

Fixes: 4d5ae32f5e1e ("net: ethernet: Add a driver for Gemini gigabit ethernet")
Link: https://lore.kernel.org/r/20260509-gemini-ethernet-fixes-v1-4-6c5d20ddc35b@kernel.org
Link: https://lore.kernel.org/r/20260512131456.189452-1-pabeni@redhat.com
Assisted-by: LLM
Reviewed-by: Joe Damato <joe@dama.to>
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/net/ethernet/cortina/gemini.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/cortina/gemini.c b/drivers/net/ethernet/cortina/gemini.c
index 4c762229ce42..1d9824d1716c 100644
--- a/drivers/net/ethernet/cortina/gemini.c
+++ b/drivers/net/ethernet/cortina/gemini.c
@@ -1450,6 +1450,7 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 	unsigned int frame_len, frag_len;
 	struct gmac_rxdesc *rx = NULL;
 	struct gmac_queue_page *gpage;
+	unsigned int received = 0;
 	union gmac_rxdesc_0 word0;
 	union gmac_rxdesc_1 word1;
 	union gmac_rxdesc_3 word3;
@@ -1545,7 +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;
+			budget--;
+			received++;
 		}
 		continue;
 
@@ -1565,7 +1567,7 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 	port->rx_skb = skb;
 	port->rx_frag_nr = frag_nr;
 	writew(r, ptr_reg);
-	return budget;
+	return received;
 }
 
 static int gmac_napi_poll(struct napi_struct *napi, int budget)
@@ -1586,7 +1588,7 @@ static int gmac_napi_poll(struct napi_struct *napi, int budget)
 		++port->rx_napi_exits;
 	}
 
-	port->freeq_refill += (budget - received);
+	port->freeq_refill += received;
 	if (port->freeq_refill > freeq_threshold) {
 		port->freeq_refill -= freeq_threshold;
 		geth_fill_freeq(geth, true);

-- 
2.55.0

[PATCH v2 2/5] net: ethernet: cortina: Finish RX updates before NAPI completion

[Linus Walleij]

napi_complete_done() releases ownership of the NAPI instance, but the
Gemini poll keeps the RX statistics writer section open and updates the
free queue after calling it. A new poll can therefore start while the old
writer is still active.

Finish the statistics and free queue updates before releasing ownership.
Only re-enable RX interrupts when napi_complete_done() reports successful
completion.

Fixes: 4d5ae32f5e1e ("net: ethernet: Add a driver for Gemini gigabit ethernet")
Suggested-by: Joe Damato <joe@dama.to>
Assisted-by: LLM
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/net/ethernet/cortina/gemini.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/cortina/gemini.c b/drivers/net/ethernet/cortina/gemini.c
index 1d9824d1716c..6502220362cb 100644
--- a/drivers/net/ethernet/cortina/gemini.c
+++ b/drivers/net/ethernet/cortina/gemini.c
@@ -1581,12 +1581,10 @@ static int gmac_napi_poll(struct napi_struct *napi, int budget)
 	u64_stats_update_begin(&port->rx_stats_syncp);
 
 	received = gmac_rx(napi->dev, budget);
-	if (received < budget) {
-		napi_gro_flush(napi, false);
-		napi_complete_done(napi, received);
-		gmac_enable_rx_irq(napi->dev, 1);
+	if (received < budget)
 		++port->rx_napi_exits;
-	}
+
+	u64_stats_update_end(&port->rx_stats_syncp);
 
 	port->freeq_refill += received;
 	if (port->freeq_refill > freeq_threshold) {
@@ -1594,7 +1592,9 @@ static int gmac_napi_poll(struct napi_struct *napi, int budget)
 		geth_fill_freeq(geth, true);
 	}
 
-	u64_stats_update_end(&port->rx_stats_syncp);
+	if (received < budget && napi_complete_done(napi, received))
+		gmac_enable_rx_irq(napi->dev, 1);
+
 	return received;
 }
 

-- 
2.55.0

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

[Linus Walleij]

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

[PATCH v2 4/5] net: ethernet: cortina: Count RX drops once per frame

[Linus Walleij]

The absence of a partial skb means either that the driver is not
assembling a frame or that the current frame was already dropped.
Consequently, repeated descriptor errors can increment rx_dropped more
than once, while an orphaned descriptor chain can reach EOF without being
counted at all.

Track the dropping state across NAPI polls. Clear it at frame boundaries
and route mapping failures and orphaned continuations through the common
drop path so each discarded frame is counted exactly once.

Fixes: 4d5ae32f5e1e ("net: ethernet: Add a driver for Gemini gigabit ethernet")
Reported-by: Joe Damato <joe@dama.to>
Closes: https://lore.kernel.org/netdev/apdK5aMmvYssz35F@devvm20253.cco0.facebook.com/
Assisted-by: LLM
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/net/ethernet/cortina/gemini.c | 41 ++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/drivers/net/ethernet/cortina/gemini.c b/drivers/net/ethernet/cortina/gemini.c
index 33e9763b32fe..9ba8524fa371 100644
--- a/drivers/net/ethernet/cortina/gemini.c
+++ b/drivers/net/ethernet/cortina/gemini.c
@@ -124,6 +124,7 @@ struct gemini_ethernet_port {
 	unsigned int		rx_coalesce_nsecs;
 	struct sk_buff		*rx_skb;
 	unsigned int		rx_frag_nr;
+	bool			rx_dropping;
 
 	unsigned int		freeq_refill;
 	struct gmac_txq		txq[TX_QUEUE_NUM];
@@ -1451,6 +1452,7 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 	struct gmac_rxdesc *rx = NULL;
 	struct gmac_queue_page *gpage;
 	unsigned int received = 0;
+	bool dropping = port->rx_dropping;
 	union gmac_rxdesc_0 word0;
 	union gmac_rxdesc_1 word1;
 	union gmac_rxdesc_3 word3;
@@ -1472,6 +1474,7 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 	w = rw.bits.wptr;
 
 	while (budget && w != r) {
+		page = NULL;
 		rx = port->rxq_ring + r;
 		word0 = rx->word0;
 		word1 = rx->word1;
@@ -1485,6 +1488,16 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 		frame_len = word1.bits.byte_count;
 		page_offs = mapping & ~PAGE_MASK;
 
+		if (word3.bits32 & SOF_BIT) {
+			if (skb) {
+				napi_free_frags(&port->napi);
+				port->stats.rx_dropped++;
+				skb = NULL;
+				frag_nr = 0;
+			}
+			dropping = false;
+		}
+
 		if (!mapping) {
 			netdev_err(netdev,
 				   "rxq[%u]: HW BUG: zero DMA desc\n", r);
@@ -1495,24 +1508,11 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 		gpage = gmac_get_queue_page(geth, port, mapping + PAGE_SIZE);
 		if (!gpage) {
 			dev_err(geth->dev, "could not find mapping\n");
-			port->stats.rx_dropped++;
-			if (skb) {
-				napi_free_frags(&port->napi);
-				skb = NULL;
-				frag_nr = 0;
-			}
-			goto next_desc;
+			goto err_drop;
 		}
 		page = gpage->page;
 
 		if (word3.bits32 & SOF_BIT) {
-			if (skb) {
-				napi_free_frags(&port->napi);
-				port->stats.rx_dropped++;
-				skb = NULL;
-				frag_nr = 0;
-			}
-
 			skb = gmac_skb_if_good_frame(port, word0, frame_len);
 			if (!skb)
 				goto err_drop;
@@ -1522,8 +1522,7 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 			frag_nr = 0;
 
 		} else if (!skb) {
-			put_page(page);
-			goto next_desc;
+			goto err_drop;
 		}
 
 		if (word3.bits32 & EOF_BIT)
@@ -1556,21 +1555,26 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 			frag_nr = 0;
 		}
 
-		if (mapping)
+		if (page)
 			put_page(page);
 
-		port->stats.rx_dropped++;
+		if (!dropping) {
+			port->stats.rx_dropped++;
+			dropping = true;
+		}
 
 next_desc:
 		/* Final or single-descriptor fragment, advance things */
 		if (word3.bits32 & EOF_BIT) {
 			budget--;
 			received++;
+			dropping = false;
 		}
 	}
 
 	port->rx_skb = skb;
 	port->rx_frag_nr = frag_nr;
+	port->rx_dropping = dropping;
 	writew(r, ptr_reg);
 	return received;
 }
@@ -1900,6 +1904,7 @@ static int gmac_stop(struct net_device *netdev)
 	napi_disable(&port->napi);
 	port->rx_skb = NULL;
 	port->rx_frag_nr = 0;
+	port->rx_dropping = false;
 
 	gmac_enable_irq(netdev, 0);
 	gmac_cleanup_rxq(netdev);

-- 
2.55.0

[PATCH v2 5/5] net: ethernet: cortina: Count RX descriptors for freeq refill

[Linus Walleij]

The software free queue provides one buffer fragment for every descriptor
moved to an RX queue. The refill heuristic instead advances by NAPI work,
which counts frames. A fragmented or discarded frame can consume several
queue entries while adding only one to the refill count.

Count the RX descriptors as they are consumed and report that separately
from NAPI work. Use the descriptor count to drive free queue refills.

Fixes: 4d5ae32f5e1e ("net: ethernet: Add a driver for Gemini gigabit ethernet")
Assisted-by: LLM
Reviewed-by: Joe Damato <joe@dama.to>
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/net/ethernet/cortina/gemini.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/cortina/gemini.c b/drivers/net/ethernet/cortina/gemini.c
index 9ba8524fa371..f08de623e6f7 100644
--- a/drivers/net/ethernet/cortina/gemini.c
+++ b/drivers/net/ethernet/cortina/gemini.c
@@ -1440,7 +1440,8 @@ static struct sk_buff *gmac_skb_if_good_frame(struct gemini_ethernet_port *port,
 	return skb;
 }
 
-static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
+static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget,
+			    unsigned int *freeq_consumed)
 {
 	struct gemini_ethernet_port *port = netdev_priv(netdev);
 	unsigned short m = (1 << port->rxq_order) - 1;
@@ -1448,6 +1449,7 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 	void __iomem *ptr_reg = port->rxq_rwptr;
 	unsigned int frag_nr = port->rx_frag_nr;
 	struct sk_buff *skb = port->rx_skb;
+	unsigned int consumed = 0;
 	unsigned int frame_len, frag_len;
 	struct gmac_rxdesc *rx = NULL;
 	struct gmac_queue_page *gpage;
@@ -1483,6 +1485,7 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 
 		r++;
 		r &= m;
+		consumed++;
 
 		frag_len = word0.bits.buffer_size;
 		frame_len = word1.bits.byte_count;
@@ -1575,6 +1578,7 @@ static unsigned int gmac_rx(struct net_device *netdev, unsigned int budget)
 	port->rx_skb = skb;
 	port->rx_frag_nr = frag_nr;
 	port->rx_dropping = dropping;
+	*freeq_consumed = consumed;
 	writew(r, ptr_reg);
 	return received;
 }
@@ -1584,18 +1588,19 @@ static int gmac_napi_poll(struct napi_struct *napi, int budget)
 	struct gemini_ethernet_port *port = netdev_priv(napi->dev);
 	struct gemini_ethernet *geth = port->geth;
 	unsigned int freeq_threshold;
+	unsigned int freeq_consumed;
 	unsigned int received;
 
 	freeq_threshold = 1 << (geth->freeq_order - 1);
 	u64_stats_update_begin(&port->rx_stats_syncp);
 
-	received = gmac_rx(napi->dev, budget);
+	received = gmac_rx(napi->dev, budget, &freeq_consumed);
 	if (received < budget)
 		++port->rx_napi_exits;
 
 	u64_stats_update_end(&port->rx_stats_syncp);
 
-	port->freeq_refill += received;
+	port->freeq_refill += freeq_consumed;
 	if (port->freeq_refill > freeq_threshold) {
 		port->freeq_refill -= freeq_threshold;
 		geth_fill_freeq(geth, true);

-- 
2.55.0