Message-Id: <1602275611-7440-1-git-send-email-loic.poulain@linaro.org>
Date:   Fri,  9 Oct 2020 22:33:31 +0200
From:   Loic Poulain <loic.poulain@...aro.org>
To:     davem@...emloft.net, hemantk@...eaurora.org
Cc:     netdev@...r.kernel.org, manivannan.sadhasivam@...aro.org,
        Loic Poulain <loic.poulain@...aro.org>
Subject: [PATCH] net: Add mhi-net driver

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>
---
 drivers/net/Kconfig   |   7 ++
 drivers/net/Makefile  |   1 +
 drivers/net/mhi_net.c | 281 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 289 insertions(+)
 create mode 100644 drivers/net/mhi_net.c

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 1368d1d..11a6357 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -426,6 +426,13 @@ config VSOCKMON
 	  mostly intended for developers or support to debug vsock issues. If
 	  unsure, say N.
 
+config MHI_NET
+	tristate "MHI network driver"
+	depends on MHI_BUS
+	help
+	  This is the network driver for MHI.  It can be used with
+	  QCOM based WWAN modems (like SDX55).  Say Y or M.
+
 endif # NET_CORE
 
 config SUNGEM_PHY
diff --git a/drivers/net/Makefile b/drivers/net/Makefile
index 94b6080..8312037 100644
--- a/drivers/net/Makefile
+++ b/drivers/net/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_GTP) += gtp.o
 obj-$(CONFIG_NLMON) += nlmon.o
 obj-$(CONFIG_NET_VRF) += vrf.o
 obj-$(CONFIG_VSOCKMON) += vsockmon.o
+obj-$(CONFIG_MHI_NET) += mhi_net.o
 
 #
 # Networking Drivers
diff --git a/drivers/net/mhi_net.c b/drivers/net/mhi_net.c
new file mode 100644
index 0000000..f66248e
--- /dev/null
+++ b/drivers/net/mhi_net.c
@@ -0,0 +1,281 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* MHI Network driver - Network over MHI
+ *
+ * Copyright (C) 2020 Linaro Ltd <loic.poulain@...aro.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>
+
+#define MIN_MTU		ETH_MIN_MTU
+#define MAX_MTU		0xffff
+#define DEFAULT_MTU	8192
+
+struct mhi_net_stats {
+	u64 rx_packets;
+	u64 rx_bytes;
+	u64 rx_errors;
+	u64 rx_dropped;
+	u64 tx_packets;
+	u64 tx_bytes;
+	u64 tx_errors;
+	u64 tx_dropped;
+	atomic_t rx_queued;
+};
+
+struct mhi_net_dev {
+	struct mhi_device *mdev;
+	struct net_device *ndev;
+	struct delayed_work rx_refill;
+	struct mhi_net_stats stats;
+};
+
+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);
+	struct mhi_device *mdev = mhi_netdev->mdev;
+	int err;
+
+	/* Only support for single buffer transfer for now */
+	err = skb_linearize(skb);
+	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);
+		netif_stop_queue(ndev);
+		return (err == -ENOMEM) ? NETDEV_TX_BUSY : err;
+	}
+
+	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;
+}
+
+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_NONE; /* QMAP... */
+	ndev->hard_header_len = 0;
+	ndev->addr_len = 0;
+	ndev->flags &= ~(IFF_BROADCAST | IFF_MULTICAST);
+	ndev->netdev_ops = &mhi_netdev_ops;
+	ndev->mtu = DEFAULT_MTU;
+	ndev->min_mtu = MIN_MTU;
+	ndev->max_mtu = MAX_MTU;
+	ndev->needs_free_netdev = true;
+	ndev->tx_queue_len = 1000;
+}
+
+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);
+}
+
+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);
+
+	if (unlikely(mhi_res->transaction_status)) {
+		mhi_netdev->stats.tx_errors++;
+	} else {
+		mhi_netdev->stats.tx_packets++;
+		mhi_netdev->stats.tx_bytes += mhi_res->bytes_xferd;
+	}
+
+	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;
+	struct sk_buff *skb;
+	int err;
+
+	if (!netif_running(ndev))
+		return;
+
+	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);
+			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;
+	}
+
+	mhi_netdev = netdev_priv(ndev);
+	dev_set_drvdata(dev, mhi_netdev);
+	mhi_netdev->ndev = ndev;
+	mhi_netdev->mdev = mhi_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;
+	}
+
+	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);
+	/* netdev released from unregister */
+}
+
+static const struct mhi_device_id mhi_net_id_table[] = {
+	{ .chan = "IP_HW0", .driver_data = (kernel_ulong_t)"mhi_hwip%d" },
+	{ .chan = "IP_SW0", .driver_data = (kernel_ulong_t)"mhi_swip%d" },
+	{}
+};
+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",
+	},
+};
+
+module_mhi_driver(mhi_net_driver);
+
+MODULE_AUTHOR("Loic Poulain <loic.poulain@...aro.org>");
+MODULE_DESCRIPTION("Network over MHI");
+MODULE_LICENSE("GPL v2");
-- 
2.7.4

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