net: mhi: Add dedicated folder

Create a dedicated mhi directory for mhi-net, mhi-net is going to
be split into differente files (for additional protocol support).

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 432 insertions, 0 deletions

diff --git a/drivers/net/mhi/Makefile b/drivers/net/mhi/Makefile
new file mode 100644
index 000000000000..0acf989a5f95
--- /dev/null
+++ b/drivers/net/mhi/Makefile
@@ -0,0 +1,3 @@
+obj-$(CONFIG_MHI_NET) += mhi_net.o
+
+mhi_net-y := net.o
diff --git a/drivers/net/mhi/net.c b/drivers/net/mhi/net.c
new file mode 100644
index 000000000000..b92c2e1f107e
--- /dev/null
+++ b/drivers/net/mhi/net.c
@@ -0,0 +1,429 @@
+// 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 rx_dropped;
+	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;
+	const struct mhi_net_proto *proto;
+	void *proto_data;
+	struct delayed_work rx_refill;
+	struct mhi_net_stats stats;
+	u32 rx_queue_sz;
+};
+
+struct mhi_net_proto {
+	int (*init)(struct mhi_net_dev *mhi_netdev);
+	struct sk_buff * (*tx_fixup)(struct mhi_net_dev *mhi_netdev, struct sk_buff *skb);
+	void (*rx)(struct mhi_net_dev *mhi_netdev, struct sk_buff *skb);
+};
+
+struct mhi_device_info {
+	const char *netname;
+	const struct mhi_net_proto *proto;
+};
+
+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 int mhi_ndo_xmit(struct sk_buff *skb, struct net_device *ndev)
+{
+	struct mhi_net_dev *mhi_netdev = netdev_priv(ndev);
+	const struct mhi_net_proto *proto = mhi_netdev->proto;
+	struct mhi_device *mdev = mhi_netdev->mdev;
+	int err;
+
+	if (proto && proto->tx_fixup) {
+		skb = proto->tx_fixup(mhi_netdev, skb);
+		if (unlikely(!skb))
+			goto exit_drop;
+	}
+
+	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);
+		stats->rx_dropped = u64_stats_read(&mhi_netdev->stats.rx_dropped);
+	} 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);
+	const struct mhi_net_proto *proto = mhi_netdev->proto;
+	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;
+		}
+
+		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);
+
+		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;
+		}
+
+		if (proto && proto->rx)
+			proto->rx(mhi_netdev, skb);
+		else
+			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;
+	int size = READ_ONCE(ndev->mtu);
+	struct sk_buff *skb;
+	int err;
+
+	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 struct device_type wwan_type = {
+	.name = "wwan",
+};
+
+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 device *dev = &mhi_dev->dev;
+	struct mhi_net_dev *mhi_netdev;
+	struct net_device *ndev;
+	int err;
+
+	ndev = alloc_netdev(sizeof(*mhi_netdev), info->netname,
+			    NET_NAME_PREDICTABLE, mhi_net_setup);
+	if (!ndev)
+		return -ENOMEM;
+
+	mhi_netdev = netdev_priv(ndev);
+	dev_set_drvdata(dev, mhi_netdev);
+	mhi_netdev->ndev = ndev;
+	mhi_netdev->mdev = mhi_dev;
+	mhi_netdev->skbagg_head = NULL;
+	mhi_netdev->proto = info->proto;
+	SET_NETDEV_DEV(ndev, &mhi_dev->dev);
+	SET_NETDEV_DEVTYPE(ndev, &wwan_type);
+
+	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)
+		goto out_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)
+		goto out_err;
+
+	if (mhi_netdev->proto) {
+		err = mhi_netdev->proto->init(mhi_netdev);
+		if (err)
+			goto out_err_proto;
+	}
+
+	return 0;
+
+out_err_proto:
+	unregister_netdev(ndev);
+out_err:
+	free_netdev(ndev);
+	return err;
+}
+
+static void mhi_net_remove(struct mhi_device *mhi_dev)
+{
+	struct mhi_net_dev *mhi_netdev = dev_get_drvdata(&mhi_dev->dev);
+
+	unregister_netdev(mhi_netdev->ndev);
+
+	mhi_unprepare_from_transfer(mhi_netdev->mdev);
+
+	if (mhi_netdev->skbagg_head)
+		kfree_skb(mhi_netdev->skbagg_head);
+
+	free_netdev(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");