Re: [PATCH net] net: bnxt: ring the doorbell when SW USO exits early

[Michael Chan]

On Tue, Aug 18, 2026 at 2:15 PM Joe Damato <joe@xxxxxxx> wrote:

> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index bc7b37cb74a7..b6cc755f7a04 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -459,8 +459,7 @@ u16 bnxt_xmit_get_cfa_action(struct sk_buff *skb)
>         return md_dst->u.port_info.port_id;
>  }
>
> -static void bnxt_txr_db_kick(struct bnxt *bp, struct bnxt_tx_ring_info *txr,
> -                            u16 prod)
> +void bnxt_txr_db_kick(struct bnxt *bp, struct bnxt_tx_ring_info *txr, u16 prod)
>  {
>         /* Sync BD data before updating doorbell */
>         wmb();
> @@ -485,6 +484,7 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)
>         struct bnxt_sw_tx_bd *tx_buf;
>         __le32 lflags = 0;
>         skb_frag_t *frag;
> +       netdev_tx_t ret;
>
>         i = skb_get_queue_mapping(skb);
>         if (unlikely(i >= bp->tx_nr_rings)) {
> @@ -510,8 +510,17 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  #endif
>         if (skb_is_gso(skb) &&
>             (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4) &&
> -           !(bp->flags & BNXT_FLAG_UDP_GSO_CAP))
> -               return bnxt_sw_udp_gso_xmit(bp, txr, txq, skb);
> +           !(bp->flags & BNXT_FLAG_UDP_GSO_CAP)) {
> +               /* if the USO code exits early (for example, it returns
> +                * NETDEV_TX_BUSY) make sure we ring any outstanding doorbells
> +                * for any BDs in the ring before returning.
> +                */
> +               ret = bnxt_sw_udp_gso_xmit(bp, txr, txq, skb);
> +               if (txr->kick_pending)
> +                       bnxt_txr_db_kick(bp, txr, txr->tx_prod);
> +
> +               return ret;
> +       }
>
>         free_size = bnxt_tx_avail(bp, txr);
>         if (unlikely(free_size < skb_shinfo(skb)->nr_frags + 2)) {
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
> index dc8ec5e5733e..60fbe3cabcf9 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
> @@ -3009,6 +3009,8 @@ int bnxt_reserve_rings(struct bnxt *bp, bool irq_re_init);
>  void bnxt_tx_disable(struct bnxt *bp);
>  void bnxt_tx_enable(struct bnxt *bp);
>  u16 bnxt_xmit_get_cfa_action(struct sk_buff *skb);
> +void bnxt_txr_db_kick(struct bnxt *bp, struct bnxt_tx_ring_info *txr,
> +                     u16 prod);
>  void bnxt_sched_reset_txr(struct bnxt *bp, struct bnxt_tx_ring_info *txr,
>                           u16 curr);
>  void bnxt_report_link(struct bnxt *bp);
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c
> index f317f60414e8..3c58b1d94ac9 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c
> @@ -223,9 +223,7 @@ netdev_tx_t bnxt_sw_udp_gso_xmit(struct bnxt *bp,
>         netdev_tx_sent_queue(txq, skb->len);
>
>         WRITE_ONCE(txr->tx_prod, prod);
> -       /* Sync BDs before doorbell */
> -       wmb();
> -       bnxt_db_write(bp, &txr->tx_db, prod);
> +       bnxt_txr_db_kick(bp, txr, prod);

The patch looks good to me.  But a slightly simpler approach is to
just set txr->kick_pending here.  Upon return, the new logic above
will always ring the doorbell for the success case.  By doing this, we
don't need to export bnxt_txr_db_kick().

But your patch is fine too, so:
Reviewed-by: Michael Chan <michael.chan@xxxxxxxxxxxx>

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