Re: [PATCH net v3] net: wwan: qcom_bam_dmux: account network packets

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 <redacted>
Reviewed-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
v3:
- Count packets discarded by the transmit error path.

v2:
- Read the TX payload length after unmapping the DMA buffer and combine the
   network-device checks.

v2: https://lore.kernel.org/netdev/20260831181006.1382372-1-sinyavin@gmail.com/ (local)
v1: https://lore.kernel.org/netdev/20260830085400.2542956-1-sinyavin@gmail.com/ (local)

Build-tested for ARM with Clang and W=1 using allmodconfig and allyesconfig.
Hardware-tested on an MDM9607-based device: three 32-byte ICMP probes completed
without loss, and the RX and TX counters each advanced by three packets and
180 bytes.

  drivers/net/wwan/qcom_bam_dmux.c | 8 ++++++++
  1 file changed, 8 insertions(+)

diff --git a/drivers/net/wwan/qcom_bam_dmux.c b/drivers/net/wwan/qcom_bam_dmux.c
index cc6ace8d6437..ef3356200b3e 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);
  }
  

@@ -368,6 +372,7 @@ static netdev_tx_t bam_dmux_netdev_start_xmit(struct sk_buff *skb,
  
  drop:
  	bam_dmux_tx_done(skb_dma);
+	dev_core_stats_tx_dropped_inc(netdev);
  	dev_kfree_skb_any(skb);
  	return NETDEV_TX_OK;
  }

@@ -402,6 +407,7 @@ 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 +427,7 @@ 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 +540,7 @@ 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