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

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>

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index b06e4c37ff617ed35261114a12b91618c6ee8d1c..263c4b67fd5a292b9e51a5b4640990acb7046f8d 100644 (file)
--- 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) {