drivers/net/mhi_net.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* MHI Network driver - Network over MHI bus
  *
  * Copyright (C) 2020 Linaro Ltd <loic.poulain@linaro.org>
  */

 #include <linux/if_arp.h>
 #include <linux/mhi.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
 #include <linux/netdevice.h>
 #include <linux/skbuff.h>
 #include <linux/u64_stats_sync.h>

 #define MHI_NET_MIN_MTU		ETH_MIN_MTU
 #define MHI_NET_MAX_MTU		0xffff
 #define MHI_NET_DEFAULT_MTU	0x4000

 struct mhi_net_stats {
 	u64_stats_t rx_packets;
 	u64_stats_t rx_bytes;
 	u64_stats_t rx_errors;
 	u64_stats_t tx_packets;
 	u64_stats_t tx_bytes;
 	u64_stats_t tx_errors;
 	u64_stats_t tx_dropped;
 	struct u64_stats_sync tx_syncp;
 	struct u64_stats_sync rx_syncp;
 };

 struct mhi_net_dev {
 	struct mhi_device *mdev;
 	struct net_device *ndev;
 	struct sk_buff *skbagg_head;
 	struct sk_buff *skbagg_tail;
 	struct delayed_work rx_refill;
 	struct mhi_net_stats stats;
 	u32 rx_queue_sz;
 	int msg_enable;
 	unsigned int mru;
 };

 struct mhi_device_info {
 	const char *netname;
 };

 static int mhi_ndo_open(struct net_device *ndev)
 {
 	struct mhi_net_dev *mhi_netdev = netdev_priv(ndev);

 	/* Feed the rx buffer pool */
 	schedule_delayed_work(&mhi_netdev->rx_refill, 0);

 	/* Carrier is established via out-of-band channel (e.g. qmi) */
 	netif_carrier_on(ndev);

 	netif_start_queue(ndev);

 	return 0;
 }

 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);

 	return 0;
 }

 static netdev_tx_t 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);
 		dev_kfree_skb_any(skb);
 		goto exit_drop;
 	}

 	if (mhi_queue_is_full(mdev, DMA_TO_DEVICE))
 		netif_stop_queue(ndev);

 	return NETDEV_TX_OK;

 exit_drop:
 	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);

 	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);
 	unsigned int start;

 	do {
 		start = u64_stats_fetch_begin_irq(&mhi_netdev->stats.rx_syncp);
 		stats->rx_packets = u64_stats_read(&mhi_netdev->stats.rx_packets);
 		stats->rx_bytes = u64_stats_read(&mhi_netdev->stats.rx_bytes);
 		stats->rx_errors = u64_stats_read(&mhi_netdev->stats.rx_errors);
 	} while (u64_stats_fetch_retry_irq(&mhi_netdev->stats.rx_syncp, start));

 	do {
 		start = u64_stats_fetch_begin_irq(&mhi_netdev->stats.tx_syncp);
 		stats->tx_packets = u64_stats_read(&mhi_netdev->stats.tx_packets);
 		stats->tx_bytes = u64_stats_read(&mhi_netdev->stats.tx_bytes);
 		stats->tx_errors = u64_stats_read(&mhi_netdev->stats.tx_errors);
 		stats->tx_dropped = u64_stats_read(&mhi_netdev->stats.tx_dropped);
 	} while (u64_stats_fetch_retry_irq(&mhi_netdev->stats.tx_syncp, start));
 }

 static const struct net_device_ops mhi_netdev_ops = {
 	.ndo_open               = mhi_ndo_open,
 	.ndo_stop               = mhi_ndo_stop,
 	.ndo_start_xmit         = mhi_ndo_xmit,
 	.ndo_get_stats64	= mhi_ndo_get_stats64,
 };

 static void mhi_net_setup(struct net_device *ndev)
 {
 	ndev->header_ops = NULL;  /* No header */
 	ndev->type = ARPHRD_RAWIP;
 	ndev->hard_header_len = 0;
 	ndev->addr_len = 0;
 	ndev->flags = IFF_POINTOPOINT | IFF_NOARP;
 	ndev->netdev_ops = &mhi_netdev_ops;
 	ndev->mtu = MHI_NET_DEFAULT_MTU;
 	ndev->min_mtu = MHI_NET_MIN_MTU;
 	ndev->max_mtu = MHI_NET_MAX_MTU;
 	ndev->tx_queue_len = 1000;
 }

 static struct sk_buff *mhi_net_skb_agg(struct mhi_net_dev *mhi_netdev,
 				       struct sk_buff *skb)
 {
 	struct sk_buff *head = mhi_netdev->skbagg_head;
 	struct sk_buff *tail = mhi_netdev->skbagg_tail;

 	/* This is non-paged skb chaining using frag_list */
 	if (!head) {
 		mhi_netdev->skbagg_head = skb;
 		return skb;
 	}

 	if (!skb_shinfo(head)->frag_list)
 		skb_shinfo(head)->frag_list = skb;
 	else
 		tail->next = skb;

 	head->len += skb->len;
 	head->data_len += skb->len;
 	head->truesize += skb->truesize;

 	mhi_netdev->skbagg_tail = skb;

 	return mhi_netdev->skbagg_head;
 }

 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 free_desc_count;

 	free_desc_count = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE);

 	if (unlikely(mhi_res->transaction_status)) {
 		switch (mhi_res->transaction_status) {
 		case -EOVERFLOW:
 			/* Packet can not fit in one MHI buffer and has been
 			 * split over multiple MHI transfers, do re-aggregation.
 			 * That usually means the device side MTU is larger than
 			 * the host side MTU/MRU. Since this is not optimal,
 			 * print a warning (once).
 			 */
 			netdev_warn_once(mhi_netdev->ndev,
 					 "Fragmented packets received, fix MTU?\n");
 			skb_put(skb, mhi_res->bytes_xferd);
 			mhi_net_skb_agg(mhi_netdev, skb);
 			break;
 		case -ENOTCONN:
 			/* MHI layer stopping/resetting the DL channel */
 			dev_kfree_skb_any(skb);
 			return;
 		default:
 			/* Unknown error, simply drop */
 			dev_kfree_skb_any(skb);
 			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);
 		}
 	} else {
 		skb_put(skb, mhi_res->bytes_xferd);

 		if (mhi_netdev->skbagg_head) {
 			/* Aggregate the final fragment */
 			skb = mhi_net_skb_agg(mhi_netdev, skb);
 			mhi_netdev->skbagg_head = NULL;
 		}

 		switch (skb->data[0] & 0xf0) {
 		case 0x40:
 			skb->protocol = htons(ETH_P_IP);
 			break;
 		case 0x60:
 			skb->protocol = htons(ETH_P_IPV6);
 			break;
 		default:
 			skb->protocol = htons(ETH_P_MAP);
 			break;
 		}

 		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, skb->len);
 		u64_stats_update_end(&mhi_netdev->stats.rx_syncp);
 		netif_rx(skb);
 	}

 	/* Refill if RX buffers queue becomes low */
 	if (free_desc_count >= 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 mhi_device *mdev = mhi_netdev->mdev;
 	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.
 	 */
 	dev_consume_skb_any(skb);

 	u64_stats_update_begin(&mhi_netdev->stats.tx_syncp);
 	if (unlikely(mhi_res->transaction_status)) {
 		/* MHI layer stopping/resetting the UL channel */
 		if (mhi_res->transaction_status == -ENOTCONN) {
 			u64_stats_update_end(&mhi_netdev->stats.tx_syncp);
 			return;
 		}

 		u64_stats_inc(&mhi_netdev->stats.tx_errors);
 	} 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) && !mhi_queue_is_full(mdev, DMA_TO_DEVICE))
 		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;
 	struct sk_buff *skb;
 	unsigned int size;
 	int err;

 	size = mhi_netdev->mru ? mhi_netdev->mru : READ_ONCE(ndev->mtu);

 	while (!mhi_queue_is_full(mdev, DMA_FROM_DEVICE)) {
 		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();
 	}

 	/* If we're still starved of rx buffers, reschedule later */
 	if (mhi_get_free_desc_count(mdev, DMA_FROM_DEVICE) == mhi_netdev->rx_queue_sz)
 		schedule_delayed_work(&mhi_netdev->rx_refill, HZ / 2);
 }

 static int mhi_net_newlink(struct mhi_device *mhi_dev, struct net_device *ndev)
 {
 	struct mhi_net_dev *mhi_netdev;
 	int err;

 	mhi_netdev = netdev_priv(ndev);

 	dev_set_drvdata(&mhi_dev->dev, mhi_netdev);
 	mhi_netdev->ndev = ndev;
 	mhi_netdev->mdev = mhi_dev;
 	mhi_netdev->skbagg_head = NULL;
 	mhi_netdev->mru = mhi_dev->mhi_cntrl->mru;

 	INIT_DELAYED_WORK(&mhi_netdev->rx_refill, mhi_net_rx_refill_work);
 	u64_stats_init(&mhi_netdev->stats.rx_syncp);
 	u64_stats_init(&mhi_netdev->stats.tx_syncp);

 	/* Start MHI channels */
 	err = mhi_prepare_for_transfer(mhi_dev);
 	if (err)
 		return err;

 	/* Number of transfer descriptors determines size of the queue */
 	mhi_netdev->rx_queue_sz = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE);

 	err = register_netdev(ndev);
 	if (err)
 		return err;

 	return 0;
 }

 static void mhi_net_dellink(struct mhi_device *mhi_dev, struct net_device *ndev)
 {
 	struct mhi_net_dev *mhi_netdev = netdev_priv(ndev);

 	unregister_netdev(ndev);

 	mhi_unprepare_from_transfer(mhi_dev);

 	kfree_skb(mhi_netdev->skbagg_head);

 	free_netdev(ndev);

 	dev_set_drvdata(&mhi_dev->dev, NULL);
 }

 static int mhi_net_probe(struct mhi_device *mhi_dev,
 			 const struct mhi_device_id *id)
 {
 	const struct mhi_device_info *info = (struct mhi_device_info *)id->driver_data;
 	struct net_device *ndev;
 	int err;

 	ndev = alloc_netdev(sizeof(struct mhi_net_dev), info->netname,
 			    NET_NAME_PREDICTABLE, mhi_net_setup);
 	if (!ndev)
 		return -ENOMEM;

 	SET_NETDEV_DEV(ndev, &mhi_dev->dev);

 	err = mhi_net_newlink(mhi_dev, ndev);
 	if (err) {
 		free_netdev(ndev);
 		return err;
 	}

 	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_net_dellink(mhi_dev, mhi_netdev->ndev);
 }

 static const struct mhi_device_info mhi_hwip0 = {
 	.netname = "mhi_hwip%d",
 };

 static const struct mhi_device_info mhi_swip0 = {
 	.netname = "mhi_swip%d",
 };

 static const struct mhi_device_id mhi_net_id_table[] = {
 	/* Hardware accelerated data PATH (to modem IPA), protocol agnostic */
 	{ .chan = "IP_HW0", .driver_data = (kernel_ulong_t)&mhi_hwip0 },
 	/* Software data PATH (to modem CPU) */
 	{ .chan = "IP_SW0", .driver_data = (kernel_ulong_t)&mhi_swip0 },
 	{}
 };
 MODULE_DEVICE_TABLE(mhi, mhi_net_id_table);

 static struct mhi_driver mhi_net_driver = {
 	.probe = mhi_net_probe,
 	.remove = mhi_net_remove,
 	.dl_xfer_cb = mhi_net_dl_callback,
 	.ul_xfer_cb = mhi_net_ul_callback,
 	.id_table = mhi_net_id_table,
 	.driver = {
 		.name = "mhi_net",
 		.owner = THIS_MODULE,
 	},
 };

 module_mhi_driver(mhi_net_driver);

 MODULE_AUTHOR("Loic Poulain <loic.poulain@linaro.org>");
 MODULE_DESCRIPTION("Network over MHI");
 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* MHI Network driver - Network over MHI bus
	*
	* Copyright (C) 2020 Linaro Ltd <loic.poulain@linaro.org>
	*/

	#include <linux/if_arp.h>
	#include <linux/mhi.h>
	#include <linux/mod_devicetable.h>
	#include <linux/module.h>
	#include <linux/netdevice.h>
	#include <linux/skbuff.h>
	#include <linux/u64_stats_sync.h>

	#define MHI_NET_MIN_MTU ETH_MIN_MTU
	#define MHI_NET_MAX_MTU 0xffff
	#define MHI_NET_DEFAULT_MTU 0x4000

	struct mhi_net_stats {
	u64_stats_t rx_packets;
	u64_stats_t rx_bytes;
	u64_stats_t rx_errors;
	u64_stats_t tx_packets;
	u64_stats_t tx_bytes;
	u64_stats_t tx_errors;
	u64_stats_t tx_dropped;
	struct u64_stats_sync tx_syncp;
	struct u64_stats_sync rx_syncp;
	};

	struct mhi_net_dev {
	struct mhi_device *mdev;
	struct net_device *ndev;
	struct sk_buff *skbagg_head;
	struct sk_buff *skbagg_tail;
	struct delayed_work rx_refill;
	struct mhi_net_stats stats;
	u32 rx_queue_sz;
	int msg_enable;
	unsigned int mru;
	};

	struct mhi_device_info {
	const char *netname;
	};

	static int mhi_ndo_open(struct net_device *ndev)
	{
	struct mhi_net_dev *mhi_netdev = netdev_priv(ndev);

	/* Feed the rx buffer pool */
	schedule_delayed_work(&mhi_netdev->rx_refill, 0);

	/* Carrier is established via out-of-band channel (e.g. qmi) */
	netif_carrier_on(ndev);

	netif_start_queue(ndev);

	return 0;
	}

	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);

	return 0;
	}

	static netdev_tx_t 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);
	dev_kfree_skb_any(skb);
	goto exit_drop;
	}

	if (mhi_queue_is_full(mdev, DMA_TO_DEVICE))
	netif_stop_queue(ndev);

	return NETDEV_TX_OK;

	exit_drop:
	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);

	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);
	unsigned int start;

	do {
	start = u64_stats_fetch_begin_irq(&mhi_netdev->stats.rx_syncp);
	stats->rx_packets = u64_stats_read(&mhi_netdev->stats.rx_packets);
	stats->rx_bytes = u64_stats_read(&mhi_netdev->stats.rx_bytes);
	stats->rx_errors = u64_stats_read(&mhi_netdev->stats.rx_errors);
	} while (u64_stats_fetch_retry_irq(&mhi_netdev->stats.rx_syncp, start));

	do {
	start = u64_stats_fetch_begin_irq(&mhi_netdev->stats.tx_syncp);
	stats->tx_packets = u64_stats_read(&mhi_netdev->stats.tx_packets);
	stats->tx_bytes = u64_stats_read(&mhi_netdev->stats.tx_bytes);
	stats->tx_errors = u64_stats_read(&mhi_netdev->stats.tx_errors);
	stats->tx_dropped = u64_stats_read(&mhi_netdev->stats.tx_dropped);
	} while (u64_stats_fetch_retry_irq(&mhi_netdev->stats.tx_syncp, start));
	}

	static const struct net_device_ops mhi_netdev_ops = {
	.ndo_open = mhi_ndo_open,
	.ndo_stop = mhi_ndo_stop,
	.ndo_start_xmit = mhi_ndo_xmit,
	.ndo_get_stats64 = mhi_ndo_get_stats64,
	};

	static void mhi_net_setup(struct net_device *ndev)
	{
	ndev->header_ops = NULL; /* No header */
	ndev->type = ARPHRD_RAWIP;
	ndev->hard_header_len = 0;
	ndev->addr_len = 0;
	ndev->flags = IFF_POINTOPOINT \| IFF_NOARP;
	ndev->netdev_ops = &mhi_netdev_ops;
	ndev->mtu = MHI_NET_DEFAULT_MTU;
	ndev->min_mtu = MHI_NET_MIN_MTU;
	ndev->max_mtu = MHI_NET_MAX_MTU;
	ndev->tx_queue_len = 1000;
	}

	static struct sk_buff mhi_net_skb_agg(struct mhi_net_dev mhi_netdev,
	struct sk_buff *skb)
	{
	struct sk_buff *head = mhi_netdev->skbagg_head;
	struct sk_buff *tail = mhi_netdev->skbagg_tail;

	/* This is non-paged skb chaining using frag_list */
	if (!head) {
	mhi_netdev->skbagg_head = skb;
	return skb;
	}

	if (!skb_shinfo(head)->frag_list)
	skb_shinfo(head)->frag_list = skb;
	else
	tail->next = skb;

	head->len += skb->len;
	head->data_len += skb->len;
	head->truesize += skb->truesize;

	mhi_netdev->skbagg_tail = skb;

	return mhi_netdev->skbagg_head;
	}

	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 free_desc_count;

	free_desc_count = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE);

	if (unlikely(mhi_res->transaction_status)) {
	switch (mhi_res->transaction_status) {
	case -EOVERFLOW:
	/* Packet can not fit in one MHI buffer and has been
	* split over multiple MHI transfers, do re-aggregation.
	* That usually means the device side MTU is larger than
	* the host side MTU/MRU. Since this is not optimal,
	* print a warning (once).
	*/
	netdev_warn_once(mhi_netdev->ndev,
	"Fragmented packets received, fix MTU?\n");
	skb_put(skb, mhi_res->bytes_xferd);
	mhi_net_skb_agg(mhi_netdev, skb);
	break;
	case -ENOTCONN:
	/* MHI layer stopping/resetting the DL channel */
	dev_kfree_skb_any(skb);
	return;
	default:
	/* Unknown error, simply drop */
	dev_kfree_skb_any(skb);
	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);
	}
	} else {
	skb_put(skb, mhi_res->bytes_xferd);

	if (mhi_netdev->skbagg_head) {
	/* Aggregate the final fragment */
	skb = mhi_net_skb_agg(mhi_netdev, skb);
	mhi_netdev->skbagg_head = NULL;
	}

	switch (skb->data[0] & 0xf0) {
	case 0x40:
	skb->protocol = htons(ETH_P_IP);
	break;
	case 0x60:
	skb->protocol = htons(ETH_P_IPV6);
	break;
	default:
	skb->protocol = htons(ETH_P_MAP);
	break;
	}

	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, skb->len);
	u64_stats_update_end(&mhi_netdev->stats.rx_syncp);
	netif_rx(skb);
	}

	/* Refill if RX buffers queue becomes low */
	if (free_desc_count >= 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 mhi_device *mdev = mhi_netdev->mdev;
	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.
	*/
	dev_consume_skb_any(skb);

	u64_stats_update_begin(&mhi_netdev->stats.tx_syncp);
	if (unlikely(mhi_res->transaction_status)) {
	/* MHI layer stopping/resetting the UL channel */
	if (mhi_res->transaction_status == -ENOTCONN) {
	u64_stats_update_end(&mhi_netdev->stats.tx_syncp);
	return;
	}

	u64_stats_inc(&mhi_netdev->stats.tx_errors);
	} 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) && !mhi_queue_is_full(mdev, DMA_TO_DEVICE))
	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;
	struct sk_buff *skb;
	unsigned int size;
	int err;

	size = mhi_netdev->mru ? mhi_netdev->mru : READ_ONCE(ndev->mtu);

	while (!mhi_queue_is_full(mdev, DMA_FROM_DEVICE)) {
	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();
	}

	/* If we're still starved of rx buffers, reschedule later */
	if (mhi_get_free_desc_count(mdev, DMA_FROM_DEVICE) == mhi_netdev->rx_queue_sz)
	schedule_delayed_work(&mhi_netdev->rx_refill, HZ / 2);
	}

	static int mhi_net_newlink(struct mhi_device mhi_dev, struct net_device ndev)
	{
	struct mhi_net_dev *mhi_netdev;
	int err;

	mhi_netdev = netdev_priv(ndev);

	dev_set_drvdata(&mhi_dev->dev, mhi_netdev);
	mhi_netdev->ndev = ndev;
	mhi_netdev->mdev = mhi_dev;
	mhi_netdev->skbagg_head = NULL;
	mhi_netdev->mru = mhi_dev->mhi_cntrl->mru;

	INIT_DELAYED_WORK(&mhi_netdev->rx_refill, mhi_net_rx_refill_work);
	u64_stats_init(&mhi_netdev->stats.rx_syncp);
	u64_stats_init(&mhi_netdev->stats.tx_syncp);

	/* Start MHI channels */
	err = mhi_prepare_for_transfer(mhi_dev);
	if (err)
	return err;

	/* Number of transfer descriptors determines size of the queue */
	mhi_netdev->rx_queue_sz = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE);

	err = register_netdev(ndev);
	if (err)
	return err;

	return 0;
	}

	static void mhi_net_dellink(struct mhi_device mhi_dev, struct net_device ndev)
	{
	struct mhi_net_dev *mhi_netdev = netdev_priv(ndev);

	unregister_netdev(ndev);

	mhi_unprepare_from_transfer(mhi_dev);

	kfree_skb(mhi_netdev->skbagg_head);

	free_netdev(ndev);

	dev_set_drvdata(&mhi_dev->dev, NULL);
	}

	static int mhi_net_probe(struct mhi_device *mhi_dev,
	const struct mhi_device_id *id)
	{
	const struct mhi_device_info info = (struct mhi_device_info )id->driver_data;
	struct net_device *ndev;
	int err;

	ndev = alloc_netdev(sizeof(struct mhi_net_dev), info->netname,
	NET_NAME_PREDICTABLE, mhi_net_setup);
	if (!ndev)
	return -ENOMEM;

	SET_NETDEV_DEV(ndev, &mhi_dev->dev);

	err = mhi_net_newlink(mhi_dev, ndev);
	if (err) {
	free_netdev(ndev);
	return err;
	}

	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_net_dellink(mhi_dev, mhi_netdev->ndev);
	}

	static const struct mhi_device_info mhi_hwip0 = {
	.netname = "mhi_hwip%d",
	};

	static const struct mhi_device_info mhi_swip0 = {
	.netname = "mhi_swip%d",
	};

	static const struct mhi_device_id mhi_net_id_table[] = {
	/* Hardware accelerated data PATH (to modem IPA), protocol agnostic */
	{ .chan = "IP_HW0", .driver_data = (kernel_ulong_t)&mhi_hwip0 },
	/* Software data PATH (to modem CPU) */
	{ .chan = "IP_SW0", .driver_data = (kernel_ulong_t)&mhi_swip0 },
	{}
	};
	MODULE_DEVICE_TABLE(mhi, mhi_net_id_table);

	static struct mhi_driver mhi_net_driver = {
	.probe = mhi_net_probe,
	.remove = mhi_net_remove,
	.dl_xfer_cb = mhi_net_dl_callback,
	.ul_xfer_cb = mhi_net_ul_callback,
	.id_table = mhi_net_id_table,
	.driver = {
	.name = "mhi_net",
	.owner = THIS_MODULE,
	},
	};

	module_mhi_driver(mhi_net_driver);

	MODULE_AUTHOR("Loic Poulain <loic.poulain@linaro.org>");
	MODULE_DESCRIPTION("Network over MHI");
	MODULE_LICENSE("GPL v2");