[PATCH net V2 2/2] net: xilinx: axienet: Fix BQL accounting for multi-BD TX packets
From: Suraj Gupta <hidden>
Date: 2026-03-27 07:33:00
Also in:
linux-arm-kernel, lkml
Subsystem:
networking drivers, the rest, xilinx axi ethernet driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Radhey Shyam Pandey
When a TX packet spans multiple buffer descriptors (scatter-gather),
axienet_free_tx_chain sums the per-BD actual length from descriptor
status into a caller-provided accumulator. That sum is reset on each
NAPI poll. If the BDs for a single packet complete across different
polls, the earlier bytes are lost and never credited to BQL. This
causes BQL to think bytes are permanently in-flight, eventually
stalling the TX queue.
The SKB pointer is stored only on the last BD of a packet. When that
BD completes, use skb->len for the byte count instead of summing
per-BD status lengths. This matches netdev_sent_queue(), which debits
skb->len, and naturally survives across polls because no partial
packet contributes to the accumulator.
Fixes: c900e49d58eb ("net: xilinx: axienet: Implement BQL")
Signed-off-by: Suraj Gupta <redacted>
---
drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index b06e4c37ff61..263c4b67fd5a 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c@@ -770,8 +770,8 @@ static int axienet_device_reset(struct net_device *ndev) * @first_bd: Index of first descriptor to clean up * @nr_bds: Max number of descriptors to clean up * @force: Whether to clean descriptors even if not complete - * @sizep: Pointer to a u32 filled with the total sum of all bytes - * in all cleaned-up descriptors. Ignored if NULL. + * @sizep: Pointer to a u32 accumulating the total byte count of + * completed packets (using skb->len). Ignored if NULL. * @budget: NAPI budget (use 0 when not called from NAPI poll) * * Would either be called after a successful transmit operation, or after
@@ -805,6 +805,8 @@ static int axienet_free_tx_chain(struct axienet_local *lp, u32 first_bd, DMA_TO_DEVICE); if (cur_p->skb && (status & XAXIDMA_BD_STS_COMPLETE_MASK)) { + if (sizep) + *sizep += cur_p->skb->len; napi_consume_skb(cur_p->skb, budget); packets++; }
@@ -818,9 +820,6 @@ static int axienet_free_tx_chain(struct axienet_local *lp, u32 first_bd, wmb(); cur_p->cntrl = 0; cur_p->status = 0; - - if (sizep) - *sizep += status & XAXIDMA_BD_STS_ACTUAL_LEN_MASK; } if (!force) {
--
2.49.1