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Date: Mon, 2 Nov 2020 14:40:15 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Loic Poulain <loic.poulain@...aro.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org,
linux-arm-msm@...r.kernel.org, bbhatt@...eaurora.org,
willemdebruijn.kernel@...il.com, jhugo@...eaurora.org,
manivannan.sadhasivam@...aro.org, hemantk@...eaurora.org
Subject: Re: [PATCH v9 2/2] net: Add mhi-net driver
On Fri, 30 Oct 2020 11:48:15 +0100 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.poulain@...aro.org>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> +static int mhi_ndo_stop(struct net_device *ndev)
> +{
> + struct mhi_net_dev *mhi_netdev = netdev_priv(ndev);
> +
> + netif_stop_queue(ndev);
> + netif_carrier_off(ndev);
> + cancel_delayed_work_sync(&mhi_netdev->rx_refill);
Where do you free the allocated skbs? Does
mhi_unprepare_from_transfer() do that?
The skbs should be freed somehow in .ndo_stop().
> + return 0;
> +}
> +
> +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;
> +
> + err = mhi_queue_skb(mdev, DMA_TO_DEVICE, skb, skb->len, MHI_EOT);
> + if (unlikely(err)) {
> + net_err_ratelimited("%s: Failed to queue TX buf (%d)\n",
> + ndev->name, err);
> +
> + u64_stats_update_begin(&mhi_netdev->stats.tx_syncp);
> + u64_stats_inc(&mhi_netdev->stats.tx_dropped);
> + u64_stats_update_end(&mhi_netdev->stats.tx_syncp);
> +
> + /* drop the packet */
> + kfree_skb(skb);
dev_kfree_skb_any()
> + }
> +
> + if (mhi_queue_is_full(mdev, DMA_TO_DEVICE))
> + netif_stop_queue(ndev);
> +
> + return NETDEV_TX_OK;
> +}
> +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;
> + int remaining;
> +
> + remaining = atomic_dec_return(&mhi_netdev->stats.rx_queued);
> +
> + if (unlikely(mhi_res->transaction_status)) {
> + u64_stats_update_begin(&mhi_netdev->stats.rx_syncp);
> + u64_stats_inc(&mhi_netdev->stats.rx_errors);
> + u64_stats_update_end(&mhi_netdev->stats.rx_syncp);
> +
> + kfree_skb(skb);
Are you sure this never runs with irqs disabled or from irq context?
Otherwise dev_kfree_skb_any().
> +
> + /* MHI layer resetting the DL channel */
> + if (mhi_res->transaction_status == -ENOTCONN)
> + return;
> + } else {
> + u64_stats_update_begin(&mhi_netdev->stats.rx_syncp);
> + u64_stats_inc(&mhi_netdev->stats.rx_packets);
> + u64_stats_add(&mhi_netdev->stats.rx_bytes, mhi_res->bytes_xferd);
> + u64_stats_update_end(&mhi_netdev->stats.rx_syncp);
> +
> + skb->protocol = htons(ETH_P_MAP);
> + skb_put(skb, mhi_res->bytes_xferd);
> + netif_rx(skb);
> + }
> +
> + /* Refill if RX buffers queue becomes low */
> + if (remaining <= mhi_netdev->rx_queue_sz / 2)
> + schedule_delayed_work(&mhi_netdev->rx_refill, 0);
> +}
> +
> +static void mhi_net_ul_callback(struct mhi_device *mhi_dev,
> + struct mhi_result *mhi_res)
> +{
> + struct mhi_net_dev *mhi_netdev = dev_get_drvdata(&mhi_dev->dev);
> + struct net_device *ndev = mhi_netdev->ndev;
> + struct sk_buff *skb = mhi_res->buf_addr;
> +
> + /* Hardware has consumed the buffer, so free the skb (which is not
> + * freed by the MHI stack) and perform accounting.
> + */
> + consume_skb(skb);
ditto
> + u64_stats_update_begin(&mhi_netdev->stats.tx_syncp);
> + if (unlikely(mhi_res->transaction_status)) {
> + u64_stats_inc(&mhi_netdev->stats.tx_errors);
> +
> + /* MHI layer resetting the UL channel */
> + if (mhi_res->transaction_status == -ENOTCONN)
> + return;
u64_stats_update_end()
> + } else {
> + u64_stats_inc(&mhi_netdev->stats.tx_packets);
> + u64_stats_add(&mhi_netdev->stats.tx_bytes, mhi_res->bytes_xferd);
> + }
> + u64_stats_update_end(&mhi_netdev->stats.tx_syncp);
> +
> + if (netif_queue_stopped(ndev))
> + netif_wake_queue(ndev);
> +}
> +
> +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;
> + int size = READ_ONCE(ndev->mtu);
> + struct sk_buff *skb;
> + int err;
> +
> + do {
should this be a while(), not a do {} while() loop now?
> + skb = netdev_alloc_skb(ndev, size);
> + if (unlikely(!skb))
> + break;
> +
> + err = mhi_queue_skb(mdev, DMA_FROM_DEVICE, skb, size, MHI_EOT);
> + if (unlikely(err)) {
> + net_err_ratelimited("%s: Failed to queue RX buf (%d)\n",
> + ndev->name, err);
> + kfree_skb(skb);
> + break;
> + }
> +
> + /* Do not hog the CPU if rx buffers are consumed faster than
> + * queued (unlikely).
> + */
> + cond_resched();
> + } while (atomic_inc_return(&mhi_netdev->stats.rx_queued) < mhi_netdev->rx_queue_sz);
> +
> + /* If we're still starved of rx buffers, reschedule later */
> + if (unlikely(!atomic_read(&mhi_netdev->stats.rx_queued)))
> + schedule_delayed_work(&mhi_netdev->rx_refill, HZ / 2);
> +}
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