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net: xilinx: axienet: Fix BQL accounting for multi-BD TX packets

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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: c900e49d58 ("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>
This commit is contained in:
Suraj Gupta
2026-03-27 13:02:38 +05:30
committed by Paolo Abeni
parent 393e0b4f17
commit d1978d03e8
1 changed files with 4 additions and 5 deletions
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9
drivers/net/ethernet/xilinx/xilinx_axienet_main.c
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@@ -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) {