[PATCH 2/2] net: Add driver for LiteX's LiteETH network interface

[Joel Stanley <joel@jms.id.au>]

LiteX is a soft system-on-chip that targets FPGAs. LiteETH is a basic
network device that is commonly used in LiteX designs.

The driver was first written in 2017 and has been maintained by the
LiteX community in various trees. Thank you to all who have contributed.

Co-developed-by: Gabriel Somlo <gsomlo@gmail.com>
Co-developed-by: David Shah <dave@ds0.me>
Co-developed-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>
---
 drivers/net/ethernet/Kconfig               |   1 +
 drivers/net/ethernet/Makefile              |   1 +
 drivers/net/ethernet/litex/Kconfig         |  24 ++
 drivers/net/ethernet/litex/Makefile        |   5 +
 drivers/net/ethernet/litex/litex_liteeth.c | 340 +++++++++++++++++++++
 5 files changed, 371 insertions(+)
 create mode 100644 drivers/net/ethernet/litex/Kconfig
 create mode 100644 drivers/net/ethernet/litex/Makefile
 create mode 100644 drivers/net/ethernet/litex/litex_liteeth.c

diff --git a/drivers/net/ethernet/Kconfig b/drivers/net/ethernet/Kconfig
index 1cdff1dca790..d796684ec9ca 100644
--- a/drivers/net/ethernet/Kconfig
+++ b/drivers/net/ethernet/Kconfig
@@ -118,6 +118,7 @@ config LANTIQ_XRX200
 	  Support for the PMAC of the Gigabit switch (GSWIP) inside the
 	  Lantiq / Intel VRX200 VDSL SoC
 
+source "drivers/net/ethernet/litex/Kconfig"
 source "drivers/net/ethernet/marvell/Kconfig"
 source "drivers/net/ethernet/mediatek/Kconfig"
 source "drivers/net/ethernet/mellanox/Kconfig"
diff --git a/drivers/net/ethernet/Makefile b/drivers/net/ethernet/Makefile
index cb3f9084a21b..aaa5078cd7d1 100644
--- a/drivers/net/ethernet/Makefile
+++ b/drivers/net/ethernet/Makefile
@@ -51,6 +51,7 @@ obj-$(CONFIG_JME) += jme.o
 obj-$(CONFIG_KORINA) += korina.o
 obj-$(CONFIG_LANTIQ_ETOP) += lantiq_etop.o
 obj-$(CONFIG_LANTIQ_XRX200) += lantiq_xrx200.o
+obj-$(CONFIG_NET_VENDOR_LITEX) += litex/
 obj-$(CONFIG_NET_VENDOR_MARVELL) += marvell/
 obj-$(CONFIG_NET_VENDOR_MEDIATEK) += mediatek/
 obj-$(CONFIG_NET_VENDOR_MELLANOX) += mellanox/
diff --git a/drivers/net/ethernet/litex/Kconfig b/drivers/net/ethernet/litex/Kconfig
new file mode 100644
index 000000000000..0a863e3ff7bf
--- /dev/null
+++ b/drivers/net/ethernet/litex/Kconfig
@@ -0,0 +1,24 @@
+#
+# LiteX device configuration
+#
+
+config NET_VENDOR_LITEX
+	bool "LiteX devices"
+	default y
+	help
+	  If you have a network (Ethernet) card belonging to this class, say Y.
+
+	  Note that the answer to this question doesn't directly affect the
+	  kernel: saying N will just cause the configurator to skip all
+	  the questions about LiteX devices. If you say Y, you will be asked
+	  for your specific card in the following questions.
+
+if NET_VENDOR_LITEX
+
+config LITEX_LITEETH
+	tristate "LiteX Ethernet support"
+	help
+	  If you wish to compile a kernel for hardware with a LiteX LiteEth
+	  device then you should answer Y to this.
+
+endif # NET_VENDOR_LITEX
diff --git a/drivers/net/ethernet/litex/Makefile b/drivers/net/ethernet/litex/Makefile
new file mode 100644
index 000000000000..9343b73b8e49
--- /dev/null
+++ b/drivers/net/ethernet/litex/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile for the LiteX network device drivers.
+#
+
+obj-$(CONFIG_LITEX_LITEETH) += litex_liteeth.o
diff --git a/drivers/net/ethernet/litex/litex_liteeth.c b/drivers/net/ethernet/litex/litex_liteeth.c
new file mode 100644
index 000000000000..48b551e6d97b
--- /dev/null
+++ b/drivers/net/ethernet/litex/litex_liteeth.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * LiteX Liteeth Ethernet
+ *
+ * Copyright 2017 Joel Stanley <joel@jms.id.au>
+ *
+ */
+
+#include <linux/etherdevice.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_net.h>
+#include <linux/of_address.h>
+#include <linux/phy.h>
+#include <linux/platform_device.h>
+#include <linux/iopoll.h>
+
+#define LITEETH_WRITER_SLOT       0x00
+#define LITEETH_WRITER_LENGTH     0x04
+#define LITEETH_WRITER_ERRORS     0x08
+#define LITEETH_WRITER_EV_STATUS  0x0C
+#define LITEETH_WRITER_EV_PENDING 0x10
+#define LITEETH_WRITER_EV_ENABLE  0x14
+#define LITEETH_READER_START      0x18
+#define LITEETH_READER_READY      0x1C
+#define LITEETH_READER_LEVEL      0x20
+#define LITEETH_READER_SLOT       0x24
+#define LITEETH_READER_LENGTH     0x28
+#define LITEETH_READER_EV_STATUS  0x2C
+#define LITEETH_READER_EV_PENDING 0x30
+#define LITEETH_READER_EV_ENABLE  0x34
+#define LITEETH_PREAMBLE_CRC      0x38
+#define LITEETH_PREAMBLE_ERRORS   0x3C
+#define LITEETH_CRC_ERRORS        0x40
+
+#define LITEETH_PHY_CRG_RESET     0x00
+#define LITEETH_MDIO_W            0x04
+#define LITEETH_MDIO_R            0x0C
+
+#define DRV_NAME	"liteeth"
+
+#define LITEETH_BUFFER_SIZE		0x800
+#define MAX_PKT_SIZE			LITEETH_BUFFER_SIZE
+
+struct liteeth {
+	void __iomem *base;
+	void __iomem *mdio_base;
+	struct net_device *netdev;
+	struct device *dev;
+	struct mii_bus *mii_bus;
+
+	/* Link management */
+	int cur_duplex;
+	int cur_speed;
+
+	/* Tx */
+	int tx_slot;
+	int num_tx_slots;
+	void __iomem *tx_base;
+
+	/* Rx */
+	int rx_slot;
+	int num_rx_slots;
+	void __iomem *rx_base;
+};
+
+
+static int liteeth_rx(struct net_device *netdev)
+{
+	struct liteeth *priv = netdev_priv(netdev);
+	struct sk_buff *skb;
+	unsigned char *data;
+	u8 rx_slot;
+	int len;
+
+	rx_slot = readb(priv->base + LITEETH_WRITER_SLOT);
+	len = readl(priv->base + LITEETH_WRITER_LENGTH);
+
+	skb = netdev_alloc_skb(netdev, len + NET_IP_ALIGN);
+	if (!skb) {
+		netdev_err(netdev, "couldn't get memory");
+		netdev->stats.rx_dropped++;
+		return NET_RX_DROP;
+	}
+
+	/* Ensure alignemnt of the ip header within the skb */
+	skb_reserve(skb, NET_IP_ALIGN);
+	if (len == 0 || len > 2048)
+		return NET_RX_DROP;
+	data = skb_put(skb, len);
+	memcpy_fromio(data, priv->rx_base + rx_slot * LITEETH_BUFFER_SIZE, len);
+	skb->protocol = eth_type_trans(skb, netdev);
+
+	netdev->stats.rx_packets++;
+	netdev->stats.rx_bytes += len;
+
+	return netif_rx(skb);
+}
+
+static irqreturn_t liteeth_interrupt(int irq, void *dev_id)
+{
+	struct net_device *netdev = dev_id;
+	struct liteeth *priv = netdev_priv(netdev);
+	u8 reg;
+
+	reg = readb(priv->base + LITEETH_READER_EV_PENDING);
+	if (reg) {
+		netdev->stats.tx_packets++;
+		writeb(reg, priv->base + LITEETH_READER_EV_PENDING);
+	}
+
+	reg = readb(priv->base + LITEETH_WRITER_EV_PENDING);
+	if (reg) {
+		liteeth_rx(netdev);
+		writeb(reg, priv->base + LITEETH_WRITER_EV_PENDING);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int liteeth_open(struct net_device *netdev)
+{
+	struct liteeth *priv = netdev_priv(netdev);
+	int err;
+
+	/* Clear pending events */
+	writeb(1, priv->base + LITEETH_WRITER_EV_PENDING);
+	writeb(1, priv->base + LITEETH_READER_EV_PENDING);
+
+	err = request_irq(netdev->irq, liteeth_interrupt, 0, netdev->name, netdev);
+	if (err) {
+		netdev_err(netdev, "failed to request irq %d\n", netdev->irq);
+		return err;
+	}
+
+	/* Enable IRQs */
+	writeb(1, priv->base + LITEETH_WRITER_EV_ENABLE);
+	writeb(1, priv->base + LITEETH_READER_EV_ENABLE);
+
+	/* TODO: Remove these once we have working mdio support */
+	priv->cur_duplex = DUPLEX_FULL;
+	priv->cur_speed = SPEED_100;
+	netif_carrier_on(netdev);
+
+	netif_start_queue(netdev);
+
+	return 0;
+}
+
+static int liteeth_stop(struct net_device *netdev)
+{
+	struct liteeth *priv = netdev_priv(netdev);
+
+	netif_stop_queue(netdev);
+
+	writeb(0, priv->base + LITEETH_WRITER_EV_ENABLE);
+	writeb(0, priv->base + LITEETH_READER_EV_ENABLE);
+
+	free_irq(netdev->irq, netdev);
+
+	return 0;
+}
+
+static int liteeth_start_xmit(struct sk_buff *skb, struct net_device *netdev)
+{
+	struct liteeth *priv = netdev_priv(netdev);
+	void __iomem *txbuffer;
+	int ret;
+	u8 val;
+
+	/* Reject oversize packets */
+	if (unlikely(skb->len > MAX_PKT_SIZE)) {
+		if (net_ratelimit())
+			netdev_dbg(netdev, "tx packet too big\n");
+		goto drop;
+	}
+
+	txbuffer = priv->tx_base + priv->tx_slot * LITEETH_BUFFER_SIZE;
+	memcpy_toio(txbuffer, skb->data, skb->len);
+	writeb(priv->tx_slot, priv->base + LITEETH_READER_SLOT);
+	writew(skb->len, priv->base + LITEETH_READER_LENGTH);
+
+	ret = readl_poll_timeout_atomic(priv->base + LITEETH_READER_READY, val, val, 5, 1000);
+	if (ret == -ETIMEDOUT) {
+		netdev_err(netdev, "LITEETH_READER_READY timed out\n");
+		goto drop;
+	}
+
+	writeb(1, priv->base + LITEETH_READER_START);
+
+	netdev->stats.tx_bytes += skb->len;
+
+	priv->tx_slot = (priv->tx_slot + 1) % priv->num_tx_slots;
+	dev_kfree_skb_any(skb);
+	return NETDEV_TX_OK;
+drop:
+	/* Drop the packet */
+	dev_kfree_skb_any(skb);
+	netdev->stats.tx_dropped++;
+
+	return NETDEV_TX_OK;
+}
+
+static const struct net_device_ops liteeth_netdev_ops = {
+	.ndo_open		= liteeth_open,
+	.ndo_stop		= liteeth_stop,
+	.ndo_start_xmit         = liteeth_start_xmit,
+};
+
+static void liteeth_reset_hw(struct liteeth *priv)
+{
+	/* Reset, twice */
+	writeb(0, priv->base + LITEETH_PHY_CRG_RESET);
+	udelay(10);
+	writeb(1, priv->base + LITEETH_PHY_CRG_RESET);
+	udelay(10);
+	writeb(0, priv->base + LITEETH_PHY_CRG_RESET);
+	udelay(10);
+}
+
+static int liteeth_probe(struct platform_device *pdev)
+{
+	struct net_device *netdev;
+	void __iomem *buf_base;
+	struct resource *res;
+	struct liteeth *priv;
+	int irq, err;
+
+	netdev = alloc_etherdev(sizeof(*priv));
+	if (!netdev)
+		return -ENOMEM;
+
+	priv = netdev_priv(netdev);
+	priv->netdev = netdev;
+	priv->dev = &pdev->dev;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "Failed to get IRQ\n");
+		goto err;
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	priv->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(priv->base)) {
+		err = PTR_ERR(priv->base);
+		goto err;
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	priv->mdio_base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(priv->mdio_base)) {
+		err = PTR_ERR(priv->mdio_base);
+		goto err;
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 2);
+	buf_base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(buf_base)) {
+		err = PTR_ERR(buf_base);
+		goto err;
+	}
+
+	err = of_property_read_u32(pdev->dev.of_node, "rx-fifo-depth",
+			&priv->num_rx_slots);
+	if (err) {
+		dev_err(&pdev->dev, "unable to get rx-fifo-depth\n");
+		goto err;
+	}
+
+	err = of_property_read_u32(pdev->dev.of_node, "tx-fifo-depth",
+			&priv->num_tx_slots);
+	if (err) {
+		dev_err(&pdev->dev, "unable to get tx-fifo-depth\n");
+		goto err;
+	}
+
+	/* Rx slots */
+	priv->rx_base = buf_base;
+	priv->rx_slot = 0;
+
+	/* Tx slots come after Rx slots */
+	priv->tx_base = buf_base + priv->num_rx_slots * LITEETH_BUFFER_SIZE;
+	priv->tx_slot = 0;
+
+	err = of_get_mac_address(pdev->dev.of_node, netdev->dev_addr);
+	if (err)
+		eth_hw_addr_random(netdev);
+
+	SET_NETDEV_DEV(netdev, &pdev->dev);
+	platform_set_drvdata(pdev, netdev);
+
+	netdev->netdev_ops = &liteeth_netdev_ops;
+	netdev->irq = irq;
+
+	liteeth_reset_hw(priv);
+
+	err = register_netdev(netdev);
+	if (err) {
+		dev_err(&pdev->dev, "Failed to register netdev\n");
+		goto err;
+	}
+
+	netdev_info(netdev, "irq %d, mapped at %px\n", netdev->irq, priv->base);
+
+	return 0;
+err:
+	free_netdev(netdev);
+	return err;
+}
+
+static int liteeth_remove(struct platform_device *pdev)
+{
+	struct net_device *netdev = platform_get_drvdata(pdev);
+
+	unregister_netdev(netdev);
+	free_netdev(netdev);
+
+	return 0;
+}
+
+static const struct of_device_id liteeth_of_match[] = {
+	{ .compatible = "litex,liteeth" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, liteeth_of_match);
+
+static struct platform_driver liteeth_driver = {
+	.probe = liteeth_probe,
+	.remove = liteeth_remove,
+	.driver = {
+		.name = DRV_NAME,
+		.of_match_table = liteeth_of_match,
+	},
+};
+module_platform_driver(liteeth_driver);
+
+MODULE_AUTHOR("Joel Stanley <joel@jms.id.au>");
+MODULE_LICENSE("GPL");
-- 
2.32.0