On Fri, 9 Oct 2020 22:33:31 +0200 Loic Poulain wrote:
> This patch adds a new network driver implementing MHI transport for
> network packets. Packets can be in any format, though QMAP (rmnet)
> is the usual protocol (flow control + PDN mux).
>
> It support two MHI devices, IP_HW0 which is, the path to the IPA
> (IP accelerator) on qcom modem, And IP_SW0 which is the software
> driven IP path (to modem CPU).
>
> Signed-off-by: Loic Poulain <loic.poul...@linaro.org>
> +static int mhi_ndo_xmit(struct sk_buff *skb, struct net_device *ndev)
> +{
> + struct mhi_net_dev *mhi_netdev = netdev_priv(ndev);
> + struct mhi_device *mdev = mhi_netdev->mdev;
> + int err;
> +
> + /* Only support for single buffer transfer for now */
> + err = skb_linearize(skb);
Since you don't advertise NETIF_F_SG you shouldn't have to call this,
no?
> + if (unlikely(err)) {
> + kfree_skb(skb);
> + mhi_netdev->stats.tx_dropped++;
> + return NETDEV_TX_OK;
> + }
> +
> + skb_tx_timestamp(skb);
> +
> + /* mhi_queue_skb is not thread-safe, but xmit is serialized by the
> + * network core. Once MHI core will be thread save, migrate to
> + * NETIF_F_LLTX support.
> + */
> + err = mhi_queue_skb(mdev, DMA_TO_DEVICE, skb, skb->len, MHI_EOT);
> + if (err) {
> + netdev_err(ndev, "mhi_queue_skb err %d\n", err);
This needs to be at least rate limited.
> + netif_stop_queue(ndev);
What's going to start the queue if it's a transient errors and not
NETDEV_TX_BUSY?
> + return (err == -ENOMEM) ? NETDEV_TX_BUSY : err;
You should drop the packet if it's not NETDEV_TX_BUSY, and return
NETDEV_TX_OK. Don't return negative errors from ndo_xmit.
> + }
> +
> + return NETDEV_TX_OK;
> +}
> +
> +static void mhi_ndo_get_stats64(struct net_device *ndev,
> + struct rtnl_link_stats64 *stats)
> +{
> + struct mhi_net_dev *mhi_netdev = netdev_priv(ndev);
> +
> + stats->rx_packets = mhi_netdev->stats.rx_packets;
> + stats->rx_bytes = mhi_netdev->stats.rx_bytes;
> + stats->rx_errors = mhi_netdev->stats.rx_errors;
> + stats->rx_dropped = mhi_netdev->stats.rx_dropped;
> + stats->tx_packets = mhi_netdev->stats.tx_packets;
> + stats->tx_bytes = mhi_netdev->stats.tx_bytes;
> + stats->tx_errors = mhi_netdev->stats.tx_errors;
> + stats->tx_dropped = mhi_netdev->stats.tx_dropped;
> +}
Can you use
> +static void mhi_net_dl_callback(struct mhi_device *mhi_dev,
> + struct mhi_result *mhi_res)
> +{
> + struct mhi_net_dev *mhi_netdev = dev_get_drvdata(&mhi_dev->dev);
> + struct sk_buff *skb = mhi_res->buf_addr;
> +
> + atomic_dec(&mhi_netdev->stats.rx_queued);
> +
> + if (mhi_res->transaction_status) {
> + mhi_netdev->stats.rx_errors++;
> + kfree_skb(skb);
> + } else {
> + mhi_netdev->stats.rx_packets++;
> + mhi_netdev->stats.rx_bytes += mhi_res->bytes_xferd;
> +
> + skb->protocol = htons(ETH_P_MAP);
> + skb_put(skb, mhi_res->bytes_xferd);
> + netif_rx(skb);
> + }
> +
> + schedule_delayed_work(&mhi_netdev->rx_refill, 0);
Scheduling a work to replace every single RX buffer looks quite
inefficient. Any chance you can do batching? I assume mhi_queue_skb()
has to be able to sleep?
> +static void mhi_net_rx_refill_work(struct work_struct *work)
> +{
> + struct mhi_net_dev *mhi_netdev = container_of(work, struct mhi_net_dev,
> + rx_refill.work);
> + struct net_device *ndev = mhi_netdev->ndev;
> + struct mhi_device *mdev = mhi_netdev->mdev;
> + struct sk_buff *skb;
> + int err;
> +
> + if (!netif_running(ndev))
> + return;
How can this happen? You cancel the work from ndo_stop.
> + do {
> + skb = netdev_alloc_skb(ndev, READ_ONCE(ndev->mtu));
> + if (unlikely(!skb)) {
> + /* If we are starved of RX buffers, retry later */
> + if (!atomic_read(&mhi_netdev->stats.rx_queued))
> + schedule_delayed_work(&mhi_netdev->rx_refill,
> HZ / 2);
> + break;
> + }
> +
> + err = mhi_queue_skb(mdev, DMA_FROM_DEVICE, skb, ndev->mtu,
> + MHI_EOT);
> + if (err) {
> + atomic_dec(&mhi_netdev->stats.rx_queued);
This can never fail with an empty ring? No need to potentially
reschedule the work here?
> + kfree_skb(skb);
> + break;
> + }
> +
> + atomic_inc(&mhi_netdev->stats.rx_queued);
> +
> + } while (1);
> +}
> +
> +static int mhi_net_probe(struct mhi_device *mhi_dev,
> + const struct mhi_device_id *id)
> +{
> + const char *netname = (char *)id->driver_data;
> + struct mhi_net_dev *mhi_netdev;
> + struct net_device *ndev;
> + struct device *dev = &mhi_dev->dev;
> + int err;
> +
> + ndev = alloc_netdev(sizeof(*mhi_netdev), netname, NET_NAME_PREDICTABLE,
> + mhi_net_setup);
> + if (!ndev) {
> + err = -ENOMEM;
> + return err;
return -ENOMEM;
> + }
> +
> + mhi_netdev = netdev_priv(ndev);
> + dev_set_drvdata(dev, mhi_netdev);
> + mhi_netdev->ndev = ndev;
> + mhi_netdev->mdev = mhi_dev;
SET_NETDEV_DEV() ?
> + INIT_DELAYED_WORK(&mhi_netdev->rx_refill, mhi_net_rx_refill_work);
> +
> + /* Start MHI channels */
> + err = mhi_prepare_for_transfer(mhi_dev, 0);
> + if (err) {
> + free_netdev(ndev);
> + return err;
> + }
> +
> + err = register_netdev(ndev);
> + if (err) {
> + dev_err(dev, "mhi_net: registering device failed\n");
> + free_netdev(ndev);
> + return -EINVAL;
Why not propagate the error?
> + }
> +
> + return 0;
> +}
> +
> +static void mhi_net_remove(struct mhi_device *mhi_dev)
> +{
> + struct mhi_net_dev *mhi_netdev = dev_get_drvdata(&mhi_dev->dev);
> +
> + mhi_unprepare_from_transfer(mhi_netdev->mdev);
> + unregister_netdev(mhi_netdev->ndev);
Isn't this the wrong way around?
Should you not unregister the netdev before you stop transfers?
> + /* netdev released from unregister */
> +}
