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Date:   Tue,  3 Aug 2021 15:36:28 +0200
From:   Loic Poulain <loic.poulain@...aro.org>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     ryazanov.s.a@...il.com, johannes@...solutions.net,
        richard.laing@...iedtelesis.co.nz, netdev@...r.kernel.org,
        Loic Poulain <loic.poulain@...aro.org>
Subject: [PATCH net-next v2 1/2] net: wwan: Add MHI MBIM network driver

Add new wwan driver for MBIM over MHI. MBIM is a transport protocol
for IP packets, allowing packet aggregation and muxing. Initially
designed for USB bus, it is also exposed through MHI bus for QCOM
based PCIe wwan modems.

This driver supports the new wwan rtnetlink interface for multi-link
management and has been tested with Quectel EM120R-GL M2 module.

Signed-off-by: Loic Poulain <loic.poulain@...aro.org>
---
 drivers/net/wwan/Kconfig         |  12 +
 drivers/net/wwan/Makefile        |   1 +
 drivers/net/wwan/mhi_wwan_mbim.c | 657 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 670 insertions(+)
 create mode 100644 drivers/net/wwan/mhi_wwan_mbim.c

diff --git a/drivers/net/wwan/Kconfig b/drivers/net/wwan/Kconfig
index de93843..77dbfc4 100644
--- a/drivers/net/wwan/Kconfig
+++ b/drivers/net/wwan/Kconfig
@@ -38,6 +38,18 @@ config MHI_WWAN_CTRL
 	  To compile this driver as a module, choose M here: the module will be
 	  called mhi_wwan_ctrl.
 
+config MHI_WWAN_MBIM
+        tristate "MHI WWAN MBIM network driver for QCOM-based PCIe modems"
+        depends on MHI_BUS
+        help
+          MHI WWAN MBIM is a WWAN network driver for QCOM-based PCIe modems.
+          It implements MBIM over MHI, for IP data aggregation and muxing.
+          A default wwan0 network interface is created for MBIM data session
+          ID 0. Additional links can be created via wwan rtnetlink type.
+
+          To compile this driver as a module, choose M here: the module will be
+          called mhi_wwan_mbim.
+
 config RPMSG_WWAN_CTRL
 	tristate "RPMSG WWAN control driver"
 	depends on RPMSG
diff --git a/drivers/net/wwan/Makefile b/drivers/net/wwan/Makefile
index d90ac33..fe51fee 100644
--- a/drivers/net/wwan/Makefile
+++ b/drivers/net/wwan/Makefile
@@ -9,5 +9,6 @@ wwan-objs += wwan_core.o
 obj-$(CONFIG_WWAN_HWSIM) += wwan_hwsim.o
 
 obj-$(CONFIG_MHI_WWAN_CTRL) += mhi_wwan_ctrl.o
+obj-$(CONFIG_MHI_WWAN_MBIM) += mhi_wwan_mbim.o
 obj-$(CONFIG_RPMSG_WWAN_CTRL) += rpmsg_wwan_ctrl.o
 obj-$(CONFIG_IOSM) += iosm/
diff --git a/drivers/net/wwan/mhi_wwan_mbim.c b/drivers/net/wwan/mhi_wwan_mbim.c
new file mode 100644
index 0000000..bb88c38
--- /dev/null
+++ b/drivers/net/wwan/mhi_wwan_mbim.c
@@ -0,0 +1,657 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* MHI MBIM Network driver - Network/MBIM over MHI bus
+ *
+ * Copyright (C) 2021 Linaro Ltd <loic.poulain@...aro.org>
+ *
+ * This driver copy some code from cdc_ncm, which is:
+ * Copyright (C) ST-Ericsson 2010-2012
+ * and cdc_mbim, which is:
+ * Copyright (c) 2012  Smith Micro Software, Inc.
+ * Copyright (c) 2012  Bjørn Mork <bjorn@...k.no>
+ *
+ */
+
+#include <linux/ethtool.h>
+#include <linux/if_arp.h>
+#include <linux/if_vlan.h>
+#include <linux/ip.h>
+#include <linux/mhi.h>
+#include <linux/mii.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/u64_stats_sync.h>
+#include <linux/usb.h>
+#include <linux/usb/cdc.h>
+#include <linux/usb/usbnet.h>
+#include <linux/usb/cdc_ncm.h>
+#include <linux/wwan.h>
+
+/* 3500 allows to optimize skb allocation, the skbs will basically fit in
+ * one 4K page. Large MBIM packets will simply be split over several MHI
+ * transfers and chained by the MHI net layer (zerocopy).
+ */
+#define MHI_DEFAULT_MRU 3500
+
+#define MHI_MBIM_DEFAULT_MTU 1500
+#define MHI_MAX_BUF_SZ 0xffff
+
+#define MBIM_NDP16_SIGN_MASK 0x00ffffff
+
+#define MHI_MBIM_LINK_HASH_SIZE 8
+#define LINK_HASH(session) ((session) % MHI_MBIM_LINK_HASH_SIZE)
+
+struct mhi_mbim_link {
+	struct mhi_mbim_context *mbim;
+	struct net_device *ndev;
+	unsigned int session;
+
+	/* 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 hlist_node hlnode;
+};
+
+struct mhi_mbim_context {
+	struct mhi_device *mdev;
+	struct sk_buff *skbagg_head;
+	struct sk_buff *skbagg_tail;
+	unsigned int mru;
+	u32 rx_queue_sz;
+	u16 rx_seq;
+	u16 tx_seq;
+	struct delayed_work rx_refill;
+	spinlock_t tx_lock;
+	struct hlist_head link_list[MHI_MBIM_LINK_HASH_SIZE];
+};
+
+struct mbim_tx_hdr {
+	struct usb_cdc_ncm_nth16 nth16;
+	struct usb_cdc_ncm_ndp16 ndp16;
+	struct usb_cdc_ncm_dpe16 dpe16[2];
+} __packed;
+
+static struct mhi_mbim_link *mhi_mbim_get_link_rcu(struct mhi_mbim_context *mbim,
+						   unsigned int session)
+{
+	struct mhi_mbim_link *link;
+
+	hlist_for_each_entry_rcu(link, &mbim->link_list[LINK_HASH(session)], hlnode) {
+		if (link->session == session)
+			return link;
+	}
+
+	return NULL;
+}
+
+static struct sk_buff *mbim_tx_fixup(struct sk_buff *skb, unsigned int session,
+				     u16 tx_seq)
+{
+	unsigned int dgram_size = skb->len;
+	struct usb_cdc_ncm_nth16 *nth16;
+	struct usb_cdc_ncm_ndp16 *ndp16;
+	struct mbim_tx_hdr *mbim_hdr;
+
+	/* Only one NDP is sent, containing the IP packet (no aggregation) */
+
+	/* Ensure we have enough headroom for crafting MBIM header */
+	if (skb_cow_head(skb, sizeof(struct mbim_tx_hdr))) {
+		dev_kfree_skb_any(skb);
+		return NULL;
+	}
+
+	mbim_hdr = skb_push(skb, sizeof(struct mbim_tx_hdr));
+
+	/* Fill NTB header */
+	nth16 = &mbim_hdr->nth16;
+	nth16->dwSignature = cpu_to_le32(USB_CDC_NCM_NTH16_SIGN);
+	nth16->wHeaderLength = cpu_to_le16(sizeof(struct usb_cdc_ncm_nth16));
+	nth16->wSequence = cpu_to_le16(tx_seq);
+	nth16->wBlockLength = cpu_to_le16(skb->len);
+	nth16->wNdpIndex = cpu_to_le16(sizeof(struct usb_cdc_ncm_nth16));
+
+	/* Fill the unique NDP */
+	ndp16 = &mbim_hdr->ndp16;
+	ndp16->dwSignature = cpu_to_le32(USB_CDC_MBIM_NDP16_IPS_SIGN | (session << 24));
+	ndp16->wLength = cpu_to_le16(sizeof(struct usb_cdc_ncm_ndp16)
+					+ sizeof(struct usb_cdc_ncm_dpe16) * 2);
+	ndp16->wNextNdpIndex = 0;
+
+	/* Datagram follows the mbim header */
+	ndp16->dpe16[0].wDatagramIndex = cpu_to_le16(sizeof(struct mbim_tx_hdr));
+	ndp16->dpe16[0].wDatagramLength = cpu_to_le16(dgram_size);
+
+	/* null termination */
+	ndp16->dpe16[1].wDatagramIndex = 0;
+	ndp16->dpe16[1].wDatagramLength = 0;
+
+	return skb;
+}
+
+static netdev_tx_t mhi_mbim_ndo_xmit(struct sk_buff *skb, struct net_device *ndev)
+{
+	struct mhi_mbim_link *link = wwan_netdev_drvpriv(ndev);
+	struct mhi_mbim_context *mbim = link->mbim;
+	unsigned long flags;
+	int err = -ENOMEM;
+
+	/* Serialize MHI channel queuing and MBIM seq */
+	spin_lock_irqsave(&mbim->tx_lock, flags);
+
+	skb = mbim_tx_fixup(skb, link->session, mbim->tx_seq);
+	if (unlikely(!skb))
+		goto exit_unlock;
+
+	err = mhi_queue_skb(mbim->mdev, DMA_TO_DEVICE, skb, skb->len, MHI_EOT);
+
+	if (mhi_queue_is_full(mbim->mdev, DMA_TO_DEVICE))
+		netif_stop_queue(ndev);
+
+	if (!err)
+		mbim->tx_seq++;
+
+exit_unlock:
+	spin_unlock_irqrestore(&mbim->tx_lock, flags);
+
+	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;
+	}
+
+	return NETDEV_TX_OK;
+
+exit_drop:
+	u64_stats_update_begin(&link->tx_syncp);
+	u64_stats_inc(&link->tx_dropped);
+	u64_stats_update_end(&link->tx_syncp);
+
+	return NETDEV_TX_OK;
+}
+
+static int mbim_rx_verify_nth16(struct mhi_mbim_context *mbim, struct sk_buff *skb)
+{
+	struct usb_cdc_ncm_nth16 *nth16;
+	int len;
+
+	if (skb->len < sizeof(struct usb_cdc_ncm_nth16) +
+			sizeof(struct usb_cdc_ncm_ndp16)) {
+		net_err_ratelimited("frame too short\n");
+		return -EINVAL;
+	}
+
+	nth16 = (struct usb_cdc_ncm_nth16 *)skb->data;
+
+	if (nth16->dwSignature != cpu_to_le32(USB_CDC_NCM_NTH16_SIGN)) {
+		net_err_ratelimited("invalid NTH16 signature <%#010x>\n",
+				    le32_to_cpu(nth16->dwSignature));
+		return -EINVAL;
+	}
+
+	/* No limit on the block length, except the size of the data pkt */
+	len = le16_to_cpu(nth16->wBlockLength);
+	if (len > skb->len) {
+		net_err_ratelimited("NTB does not fit into the skb %u/%u\n",
+				    len, skb->len);
+		return -EINVAL;
+	}
+
+	if (mbim->rx_seq + 1 != le16_to_cpu(nth16->wSequence) &&
+	    (mbim->rx_seq || le16_to_cpu(nth16->wSequence)) &&
+	    !(mbim->rx_seq == 0xffff && !le16_to_cpu(nth16->wSequence))) {
+		net_err_ratelimited("sequence number glitch prev=%d curr=%d\n",
+				    mbim->rx_seq, le16_to_cpu(nth16->wSequence));
+	}
+	mbim->rx_seq = le16_to_cpu(nth16->wSequence);
+
+	return le16_to_cpu(nth16->wNdpIndex);
+}
+
+static int mbim_rx_verify_ndp16(struct sk_buff *skb, struct usb_cdc_ncm_ndp16 *ndp16)
+{
+	int ret;
+
+	if (le16_to_cpu(ndp16->wLength) < USB_CDC_NCM_NDP16_LENGTH_MIN) {
+		net_err_ratelimited("invalid DPT16 length <%u>\n",
+				    le16_to_cpu(ndp16->wLength));
+		return -EINVAL;
+	}
+
+	ret = ((le16_to_cpu(ndp16->wLength) - sizeof(struct usb_cdc_ncm_ndp16))
+			/ sizeof(struct usb_cdc_ncm_dpe16));
+	ret--; /* Last entry is always a NULL terminator */
+
+	if (sizeof(struct usb_cdc_ncm_ndp16) +
+	     ret * sizeof(struct usb_cdc_ncm_dpe16) > skb->len) {
+		net_err_ratelimited("Invalid nframes = %d\n", ret);
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+static void mhi_mbim_rx(struct mhi_mbim_context *mbim, struct sk_buff *skb)
+{
+	int ndpoffset;
+
+	/* Check NTB header and retrieve first NDP offset */
+	ndpoffset = mbim_rx_verify_nth16(mbim, skb);
+	if (ndpoffset < 0) {
+		net_err_ratelimited("mbim: Incorrect NTB header\n");
+		goto error;
+	}
+
+	/* Process each NDP */
+	while (1) {
+		struct usb_cdc_ncm_ndp16 ndp16;
+		struct usb_cdc_ncm_dpe16 dpe16;
+		struct mhi_mbim_link *link;
+		int nframes, n, dpeoffset;
+		unsigned int session;
+
+		if (skb_copy_bits(skb, ndpoffset, &ndp16, sizeof(ndp16))) {
+			net_err_ratelimited("mbim: Incorrect NDP offset (%u)\n",
+					    ndpoffset);
+			goto error;
+		}
+
+		/* Check NDP header and retrieve number of datagrams */
+		nframes = mbim_rx_verify_ndp16(skb, &ndp16);
+		if (nframes < 0) {
+			net_err_ratelimited("mbim: Incorrect NDP16\n");
+			goto error;
+		}
+
+		 /* Only IP data type supported, no DSS in MHI context */
+		if ((ndp16.dwSignature & cpu_to_le32(MBIM_NDP16_SIGN_MASK))
+				!= cpu_to_le32(USB_CDC_MBIM_NDP16_IPS_SIGN)) {
+			net_err_ratelimited("mbim: Unsupported NDP type\n");
+			goto next_ndp;
+		}
+
+		session = (le32_to_cpu(ndp16.dwSignature) & ~MBIM_NDP16_SIGN_MASK) >> 24;
+
+		rcu_read_lock();
+
+		link = mhi_mbim_get_link_rcu(mbim, session);
+		if (!link) {
+			net_err_ratelimited("mbim: bad packet session (%u)\n", session);
+			goto unlock;
+		}
+
+		/* de-aggregate and deliver IP packets */
+		dpeoffset = ndpoffset + sizeof(struct usb_cdc_ncm_ndp16);
+		for (n = 0; n < nframes; n++, dpeoffset += sizeof(dpe16)) {
+			u16 dgram_offset, dgram_len;
+			struct sk_buff *skbn;
+
+			if (skb_copy_bits(skb, dpeoffset, &dpe16, sizeof(dpe16)))
+				break;
+
+			dgram_offset = le16_to_cpu(dpe16.wDatagramIndex);
+			dgram_len = le16_to_cpu(dpe16.wDatagramLength);
+
+			if (!dgram_offset || !dgram_len)
+				break; /* null terminator */
+
+			skbn = netdev_alloc_skb(link->ndev, dgram_len);
+			if (!skbn)
+				continue;
+
+			skb_put(skbn, dgram_len);
+			skb_copy_bits(skb, dgram_offset, skbn->data, dgram_len);
+
+			switch (skbn->data[0] & 0xf0) {
+			case 0x40:
+				skbn->protocol = htons(ETH_P_IP);
+				break;
+			case 0x60:
+				skbn->protocol = htons(ETH_P_IPV6);
+				break;
+			default:
+				net_err_ratelimited("%s: unknown protocol\n",
+						    link->ndev->name);
+				dev_kfree_skb_any(skbn);
+				u64_stats_update_begin(&link->rx_syncp);
+				u64_stats_inc(&link->rx_errors);
+				u64_stats_update_end(&link->rx_syncp);
+				continue;
+			}
+
+			u64_stats_update_begin(&link->rx_syncp);
+			u64_stats_inc(&link->rx_packets);
+			u64_stats_add(&link->rx_bytes, skbn->len);
+			u64_stats_update_end(&link->rx_syncp);
+
+			netif_rx(skbn);
+		}
+unlock:
+		rcu_read_unlock();
+next_ndp:
+		/* Other NDP to process? */
+		ndpoffset = (int)le16_to_cpu(ndp16.wNextNdpIndex);
+		if (!ndpoffset)
+			break;
+	}
+
+	/* free skb */
+	dev_consume_skb_any(skb);
+	return;
+error:
+	dev_kfree_skb_any(skb);
+}
+
+static struct sk_buff *mhi_net_skb_agg(struct mhi_mbim_context *mbim,
+				       struct sk_buff *skb)
+{
+	struct sk_buff *head = mbim->skbagg_head;
+	struct sk_buff *tail = mbim->skbagg_tail;
+
+	/* This is non-paged skb chaining using frag_list */
+	if (!head) {
+		mbim->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;
+
+	mbim->skbagg_tail = skb;
+
+	return mbim->skbagg_head;
+}
+
+static void mhi_net_rx_refill_work(struct work_struct *work)
+{
+	struct mhi_mbim_context *mbim = container_of(work, struct mhi_mbim_context,
+						     rx_refill.work);
+	struct mhi_device *mdev = mbim->mdev;
+	int err;
+
+	while (!mhi_queue_is_full(mdev, DMA_FROM_DEVICE)) {
+		struct sk_buff *skb = alloc_skb(MHI_DEFAULT_MRU, GFP_KERNEL);
+
+		if (unlikely(!skb))
+			break;
+
+		err = mhi_queue_skb(mdev, DMA_FROM_DEVICE, skb,
+				    MHI_DEFAULT_MRU, MHI_EOT);
+		if (unlikely(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) == mbim->rx_queue_sz)
+		schedule_delayed_work(&mbim->rx_refill, HZ / 2);
+}
+
+static void mhi_mbim_dl_callback(struct mhi_device *mhi_dev,
+				 struct mhi_result *mhi_res)
+{
+	struct mhi_mbim_context *mbim = 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 has been split over multiple transfers */
+			skb_put(skb, mhi_res->bytes_xferd);
+			mhi_net_skb_agg(mbim, 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);
+		}
+	} else {
+		skb_put(skb, mhi_res->bytes_xferd);
+
+		if (mbim->skbagg_head) {
+			/* Aggregate the final fragment */
+			skb = mhi_net_skb_agg(mbim, skb);
+			mbim->skbagg_head = NULL;
+		}
+
+		mhi_mbim_rx(mbim, skb);
+	}
+
+	/* Refill if RX buffers queue becomes low */
+	if (free_desc_count >= mbim->rx_queue_sz / 2)
+		schedule_delayed_work(&mbim->rx_refill, 0);
+}
+
+static void mhi_mbim_ndo_get_stats64(struct net_device *ndev,
+				     struct rtnl_link_stats64 *stats)
+{
+	struct mhi_mbim_link *link = wwan_netdev_drvpriv(ndev);
+	unsigned int start;
+
+	do {
+		start = u64_stats_fetch_begin_irq(&link->rx_syncp);
+		stats->rx_packets = u64_stats_read(&link->rx_packets);
+		stats->rx_bytes = u64_stats_read(&link->rx_bytes);
+		stats->rx_errors = u64_stats_read(&link->rx_errors);
+	} while (u64_stats_fetch_retry_irq(&link->rx_syncp, start));
+
+	do {
+		start = u64_stats_fetch_begin_irq(&link->tx_syncp);
+		stats->tx_packets = u64_stats_read(&link->tx_packets);
+		stats->tx_bytes = u64_stats_read(&link->tx_bytes);
+		stats->tx_errors = u64_stats_read(&link->tx_errors);
+		stats->tx_dropped = u64_stats_read(&link->tx_dropped);
+	} while (u64_stats_fetch_retry_irq(&link->tx_syncp, start));
+}
+
+static void mhi_mbim_ul_callback(struct mhi_device *mhi_dev,
+				 struct mhi_result *mhi_res)
+{
+	struct mhi_mbim_context *mbim = dev_get_drvdata(&mhi_dev->dev);
+	struct sk_buff *skb = mhi_res->buf_addr;
+	struct net_device *ndev = skb->dev;
+	struct mhi_mbim_link *link = wwan_netdev_drvpriv(ndev);
+
+	/* 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(&link->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(&link->tx_syncp);
+			return;
+		}
+
+		u64_stats_inc(&link->tx_errors);
+	} else {
+		u64_stats_inc(&link->tx_packets);
+		u64_stats_add(&link->tx_bytes, mhi_res->bytes_xferd);
+	}
+	u64_stats_update_end(&link->tx_syncp);
+
+	if (netif_queue_stopped(ndev) && !mhi_queue_is_full(mbim->mdev, DMA_TO_DEVICE))
+		netif_wake_queue(ndev);
+}
+
+static int mhi_mbim_ndo_open(struct net_device *ndev)
+{
+	struct mhi_mbim_link *link = wwan_netdev_drvpriv(ndev);
+
+	/* Feed the MHI rx buffer pool */
+	schedule_delayed_work(&link->mbim->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_mbim_ndo_stop(struct net_device *ndev)
+{
+	netif_stop_queue(ndev);
+	netif_carrier_off(ndev);
+
+	return 0;
+}
+
+static const struct net_device_ops mhi_mbim_ndo = {
+	.ndo_open = mhi_mbim_ndo_open,
+	.ndo_stop = mhi_mbim_ndo_stop,
+	.ndo_start_xmit = mhi_mbim_ndo_xmit,
+	.ndo_get_stats64 = mhi_mbim_ndo_get_stats64,
+};
+
+static int mhi_mbim_newlink(void *ctxt, struct net_device *ndev, u32 if_id,
+			    struct netlink_ext_ack *extack)
+{
+	struct mhi_mbim_link *link = wwan_netdev_drvpriv(ndev);
+	struct mhi_mbim_context *mbim = ctxt;
+
+	link->session = if_id;
+	link->mbim = mbim;
+	link->ndev = ndev;
+	u64_stats_init(&link->rx_syncp);
+	u64_stats_init(&link->tx_syncp);
+
+	rcu_read_lock();
+	if (mhi_mbim_get_link_rcu(mbim, if_id)) {
+		rcu_read_unlock();
+		return -EEXIST;
+	}
+	rcu_read_unlock();
+
+	/* Already protected by RTNL lock */
+	hlist_add_head_rcu(&link->hlnode, &mbim->link_list[LINK_HASH(if_id)]);
+
+	return register_netdevice(ndev);
+}
+
+static void mhi_mbim_dellink(void *ctxt, struct net_device *ndev,
+			     struct list_head *head)
+{
+	struct mhi_mbim_link *link = wwan_netdev_drvpriv(ndev);
+
+	hlist_del_init_rcu(&link->hlnode);
+	synchronize_rcu();
+
+	unregister_netdevice_queue(ndev, head);
+}
+
+static void mhi_mbim_setup(struct net_device *ndev)
+{
+	ndev->header_ops = NULL;  /* No header */
+	ndev->type = ARPHRD_RAWIP;
+	ndev->needed_headroom = sizeof(struct mbim_tx_hdr);
+	ndev->hard_header_len = 0;
+	ndev->addr_len = 0;
+	ndev->flags = IFF_POINTOPOINT | IFF_NOARP;
+	ndev->netdev_ops = &mhi_mbim_ndo;
+	ndev->mtu = MHI_MBIM_DEFAULT_MTU;
+	ndev->min_mtu = ETH_MIN_MTU;
+	ndev->max_mtu = MHI_MAX_BUF_SZ - ndev->needed_headroom;
+	ndev->tx_queue_len = 1000;
+}
+
+static const struct wwan_ops mhi_mbim_wwan_ops = {
+	.priv_size = sizeof(struct mhi_mbim_link),
+	.setup = mhi_mbim_setup,
+	.newlink = mhi_mbim_newlink,
+	.dellink = mhi_mbim_dellink,
+};
+
+static int mhi_mbim_probe(struct mhi_device *mhi_dev, const struct mhi_device_id *id)
+{
+	struct mhi_controller *cntrl = mhi_dev->mhi_cntrl;
+	struct mhi_mbim_context *mbim;
+	int err;
+
+	mbim = devm_kzalloc(&mhi_dev->dev, sizeof(*mbim), GFP_KERNEL);
+	if (!mbim)
+		return -ENOMEM;
+
+	dev_set_drvdata(&mhi_dev->dev, mbim);
+	mbim->mdev = mhi_dev;
+	mbim->mru = mhi_dev->mhi_cntrl->mru ? mhi_dev->mhi_cntrl->mru : MHI_DEFAULT_MRU;
+
+	INIT_DELAYED_WORK(&mbim->rx_refill, mhi_net_rx_refill_work);
+
+	/* Start MHI channels */
+	err = mhi_prepare_for_transfer(mhi_dev);
+	if (err)
+		return err;
+
+	/* Number of transfer descriptors determines size of the queue */
+	mbim->rx_queue_sz = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE);
+
+	/* Register wwan link ops with MHI controller representing WWAN instance */
+	return wwan_register_ops(&cntrl->mhi_dev->dev, &mhi_mbim_wwan_ops, mbim, 0);
+}
+
+static void mhi_mbim_remove(struct mhi_device *mhi_dev)
+{
+	struct mhi_mbim_context *mbim = dev_get_drvdata(&mhi_dev->dev);
+	struct mhi_controller *cntrl = mhi_dev->mhi_cntrl;
+
+	mhi_unprepare_from_transfer(mhi_dev);
+	cancel_delayed_work_sync(&mbim->rx_refill);
+	wwan_unregister_ops(&cntrl->mhi_dev->dev);
+	kfree_skb(mbim->skbagg_head);
+	dev_set_drvdata(&mhi_dev->dev, NULL);
+}
+
+static const struct mhi_device_id mhi_mbim_id_table[] = {
+	/* Hardware accelerated data PATH (to modem IPA), MBIM protocol */
+	{ .chan = "IP_HW0_MBIM", .driver_data = 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(mhi, mhi_mbim_id_table);
+
+static struct mhi_driver mhi_mbim_driver = {
+	.probe = mhi_mbim_probe,
+	.remove = mhi_mbim_remove,
+	.dl_xfer_cb = mhi_mbim_dl_callback,
+	.ul_xfer_cb = mhi_mbim_ul_callback,
+	.id_table = mhi_mbim_id_table,
+	.driver = {
+		.name = "mhi_wwan_mbim",
+		.owner = THIS_MODULE,
+	},
+};
+
+module_mhi_driver(mhi_mbim_driver);
+
+MODULE_AUTHOR("Loic Poulain <loic.poulain@...aro.org>");
+MODULE_DESCRIPTION("Network/MBIM over MHI");
+MODULE_LICENSE("GPL v2");
-- 
2.7.4

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