[PATCH 6.19 074/311] net: xilinx: axienet: Fix BQL accounting for multi-BD TX packets

Greg Kroah-Hartman
2026-04-08T18:54:21Z

From: Suraj Gupta <suraj.gupta2@amd.com>

[ Upstream commit d1978d03e86785872871bff9c2623174b10740de ]

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 <suraj.gupta2@amd.com>
Reviewed-by: Sean Anderson <sean.anderson@linux.dev>
Link: https://patch.msgid.link/20260327073238.134948-3-suraj.gupta2@amd.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 284031fb2e2c7..eefe54ce66852 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) {
--
2.53.0