Re: [PATCH net v2] net: wwan: qcom_bam_dmux: account network packets

[Loic Poulain]

On Mon, Aug 31, 2026 at 8:10 PM Dmitry Sinyavin <sinyavin@xxxxxxxxx> wrote:
>
> The BAM-DMUX data path does not update the network device packet and byte
> counters. As a result, userspace sees zero traffic even while packets are
> being transferred.
>
> Use the standard per-CPU software statistics helpers. Account transmitted
> packets after their DMA completion and received packets after removing the
> BAM-DMUX header and padding.
>
> Fixes: 21a0ffd9b38c ("net: wwan: Add Qualcomm BAM-DMUX WWAN network driver")
> Signed-off-by: Dmitry Sinyavin <sinyavin@xxxxxxxxx>

Looks good to me. Since you're touching the statistics accounting, it
would also make sense to update the drop statistics, for example by
incrementing the TX drop counter in the xmit drop path.

Reviewed-by: Loic Poulain <loic.poulain@xxxxxxxxxxxxxxxx>


> ---
> v2:
> - Read the TX payload length after unmapping the DMA buffer and combine the
>   network-device checks.
>
> v1: https://lore.kernel.org/netdev/20260830085400.2542956-1-sinyavin@xxxxxxxxx/
>
> Build-tested for ARM with Clang and W=1 using allmodconfig and allyesconfig.
> Hardware-tested on Qualcomm MDM9607: three 32-byte IPv4 probes completed
> without loss and added three packets and 180 bytes in each direction.
>
>  drivers/net/wwan/qcom_bam_dmux.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/net/wwan/qcom_bam_dmux.c b/drivers/net/wwan/qcom_bam_dmux.c
> index cc6ace8d6437..5bcac2ccaabd 100644
> --- a/drivers/net/wwan/qcom_bam_dmux.c
> +++ b/drivers/net/wwan/qcom_bam_dmux.c
> @@ -177,8 +177,12 @@ static void bam_dmux_tx_callback(void *data)
>  {
>         struct bam_dmux_skb_dma *skb_dma = data;
>         struct sk_buff *skb = skb_dma->skb;
> +       struct net_device *netdev = skb->dev;
>
>         bam_dmux_tx_done(skb_dma);
> +       if (netdev)
> +               dev_sw_netstats_tx_add(netdev, 1,
> +                                      ((struct bam_dmux_hdr *)skb->data)->len);
>         dev_consume_skb_any(skb);
>  }
>
> @@ -402,6 +406,7 @@ static const struct net_device_ops bam_dmux_ops = {
>         .ndo_open       = bam_dmux_netdev_open,
>         .ndo_stop       = bam_dmux_netdev_stop,
>         .ndo_start_xmit = bam_dmux_netdev_start_xmit,
> +       .ndo_get_stats64        = dev_get_tstats64,
>  };
>
>  static const struct device_type wwan_type = {
> @@ -421,6 +426,7 @@ static void bam_dmux_netdev_setup(struct net_device *dev)
>         dev->needed_headroom = sizeof(struct bam_dmux_hdr);
>         dev->needed_tailroom = sizeof(u32); /* word-aligned */
>         dev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
> +       dev->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;
>
>         /* This perm addr will be used as interface identifier by IPv6 */
>         dev->addr_assign_type = NET_ADDR_RANDOM;
> @@ -533,6 +539,7 @@ static void bam_dmux_cmd_data(struct bam_dmux_skb_dma *skb_dma)
>                 break;
>         }
>
> +       dev_sw_netstats_rx_add(netdev, skb->len);
>         netif_receive_skb(skb);
>  }
>
>
> base-commit: 2188569e7e1b0bc3f3b557dc97ab7a02befc11c8
> --
> 2.53.0