net: broadcom: bcm4908enet: add BCM4908 controller driver

BCM4908 SoCs family uses Ethernel controller that includes UniMAC but
uses different DMA engine (than other controllers) and requires
different programming.
Signed-off-by: NRafał Miłecki <rafal@milecki.pl>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -3445,6 +3445,15 @@ F:	Documentation/devicetree/bindings/mips/brcm/
 F:	arch/mips/bcm47xx/*
 F:	arch/mips/include/asm/mach-bcm47xx/*
 
+BROADCOM BCM4908 ETHERNET DRIVER
+M:	Rafał Miłecki <rafal@milecki.pl>
+M:	bcm-kernel-feedback-list@broadcom.com
+L:	netdev@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/net/brcm,bcm4908enet.yaml
+F:	drivers/net/ethernet/broadcom/bcm4908enet.*
+F:	drivers/net/ethernet/broadcom/unimac.h
+
 BROADCOM BCM5301X ARM ARCHITECTURE
 M:	Hauke Mehrtens <hauke@hauke-m.de>
 M:	Rafał Miłecki <zajec5@gmail.com>

drivers/net/ethernet/broadcom/Kconfig

@@ -51,6 +51,14 @@ config B44_PCI
 	depends on B44_PCI_AUTOSELECT && B44_PCICORE_AUTOSELECT
 	default y
 
+config BCM4908ENET
+	tristate "Broadcom BCM4908 internal mac support"
+	depends on ARCH_BCM4908 || COMPILE_TEST
+	default y
+	help
+	  This driver supports Ethernet controller integrated into Broadcom
+	  BCM4908 family SoCs.
+
 config BCM63XX_ENET
 	tristate "Broadcom 63xx internal mac support"
 	depends on BCM63XX

drivers/net/ethernet/broadcom/Makefile

@@ -4,6 +4,7 @@
 #
 
 obj-$(CONFIG_B44) += b44.o
+obj-$(CONFIG_BCM4908ENET) += bcm4908enet.o
 obj-$(CONFIG_BCM63XX_ENET) += bcm63xx_enet.o
 obj-$(CONFIG_BCMGENET) += genet/
 obj-$(CONFIG_BNX2) += bnx2.o

drivers/net/ethernet/broadcom/bcm4908enet.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 Rafał Miłecki <rafal@milecki.pl>
+ */
+
+#include <linux/delay.h>
+#include <linux/etherdevice.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+#include "bcm4908enet.h"
+#include "unimac.h"
+
+#define ENET_DMA_CH_RX_CFG			ENET_DMA_CH0_CFG
+#define ENET_DMA_CH_TX_CFG			ENET_DMA_CH1_CFG
+#define ENET_DMA_CH_RX_STATE_RAM		ENET_DMA_CH0_STATE_RAM
+#define ENET_DMA_CH_TX_STATE_RAM		ENET_DMA_CH1_STATE_RAM
+
+#define ENET_TX_BDS_NUM				200
+#define ENET_RX_BDS_NUM				200
+#define ENET_RX_BDS_NUM_MAX			8192
+
+#define ENET_DMA_INT_DEFAULTS			(ENET_DMA_CH_CFG_INT_DONE | \
+						 ENET_DMA_CH_CFG_INT_NO_DESC | \
+						 ENET_DMA_CH_CFG_INT_BUFF_DONE)
+#define ENET_DMA_MAX_BURST_LEN			8 /* in 64 bit words */
+
+#define ENET_MTU_MIN				60
+#define ENET_MTU_MAX				1500 /* Is it possible to support 2044? */
+#define ENET_MTU_MAX_EXTRA_SIZE			32 /* L2 */
+
+struct bcm4908enet_dma_ring_bd {
+	__le32 ctl;
+	__le32 addr;
+} __packed;
+
+struct bcm4908enet_dma_ring_slot {
+	struct sk_buff *skb;
+	unsigned int len;
+	dma_addr_t dma_addr;
+};
+
+struct bcm4908enet_dma_ring {
+	int is_tx;
+	int read_idx;
+	int write_idx;
+	int length;
+	u16 cfg_block;
+	u16 st_ram_block;
+
+	union {
+		void *cpu_addr;
+		struct bcm4908enet_dma_ring_bd *buf_desc;
+	};
+	dma_addr_t dma_addr;
+
+	struct bcm4908enet_dma_ring_slot *slots;
+};
+
+struct bcm4908enet {
+	struct device *dev;
+	struct net_device *netdev;
+	struct napi_struct napi;
+	void __iomem *base;
+
+	struct bcm4908enet_dma_ring tx_ring;
+	struct bcm4908enet_dma_ring rx_ring;
+};
+
+/***
+ * R/W ops
+ */
+
+static inline u32 enet_read(struct bcm4908enet *enet, u16 offset)
+{
+	return readl(enet->base + offset);
+}
+
+static inline void enet_write(struct bcm4908enet *enet, u16 offset, u32 value)
+{
+	writel(value, enet->base + offset);
+}
+
+static inline void enet_maskset(struct bcm4908enet *enet, u16 offset, u32 mask, u32 set)
+{
+	u32 val;
+
+	WARN_ON(set & ~mask);
+
+	val = enet_read(enet, offset);
+	val = (val & ~mask) | (set & mask);
+	enet_write(enet, offset, val);
+}
+
+static inline void enet_set(struct bcm4908enet *enet, u16 offset, u32 set)
+{
+	enet_maskset(enet, offset, set, set);
+}
+
+static inline u32 enet_umac_read(struct bcm4908enet *enet, u16 offset)
+{
+	return enet_read(enet, ENET_UNIMAC + offset);
+}
+
+static inline void enet_umac_write(struct bcm4908enet *enet, u16 offset, u32 value)
+{
+	enet_write(enet, ENET_UNIMAC + offset, value);
+}
+
+static inline void enet_umac_maskset(struct bcm4908enet *enet, u16 offset, u32 mask, u32 set)
+{
+	enet_maskset(enet, ENET_UNIMAC + offset, mask, set);
+}
+
+static inline void enet_umac_set(struct bcm4908enet *enet, u16 offset, u32 set)
+{
+	enet_set(enet, ENET_UNIMAC + offset, set);
+}
+
+/***
+ * Helpers
+ */
+
+static void bcm4908enet_intrs_on(struct bcm4908enet *enet)
+{
+	enet_write(enet, ENET_DMA_CH_RX_CFG + ENET_DMA_CH_CFG_INT_MASK, ENET_DMA_INT_DEFAULTS);
+}
+
+static void bcm4908enet_intrs_off(struct bcm4908enet *enet)
+{
+	enet_write(enet, ENET_DMA_CH_RX_CFG + ENET_DMA_CH_CFG_INT_MASK, 0);
+}
+
+static void bcm4908enet_intrs_ack(struct bcm4908enet *enet)
+{
+	enet_write(enet, ENET_DMA_CH_RX_CFG + ENET_DMA_CH_CFG_INT_STAT, ENET_DMA_INT_DEFAULTS);
+}
+
+/***
+ * DMA
+ */
+
+static int bcm4908_dma_alloc_buf_descs(struct bcm4908enet *enet, struct bcm4908enet_dma_ring *ring)
+{
+	int size = ring->length * sizeof(struct bcm4908enet_dma_ring_bd);
+	struct device *dev = enet->dev;
+
+	ring->cpu_addr = dma_alloc_coherent(dev, size, &ring->dma_addr, GFP_KERNEL);
+	if (!ring->cpu_addr)
+		return -ENOMEM;
+
+	if (((uintptr_t)ring->cpu_addr) & (0x40 - 1)) {
+		dev_err(dev, "Invalid DMA ring alignment\n");
+		goto err_free_buf_descs;
+	}
+
+	ring->slots = kzalloc(ring->length * sizeof(*ring->slots), GFP_KERNEL);
+	if (!ring->slots)
+		goto err_free_buf_descs;
+
+	memset(ring->cpu_addr, 0, size);
+
+	ring->read_idx = 0;
+	ring->write_idx = 0;
+
+	return 0;
+
+err_free_buf_descs:
+	dma_free_coherent(dev, size, ring->cpu_addr, ring->dma_addr);
+	return -ENOMEM;
+}
+
+static void bcm4908enet_dma_free(struct bcm4908enet *enet)
+{
+	struct bcm4908enet_dma_ring *tx_ring = &enet->tx_ring;
+	struct bcm4908enet_dma_ring *rx_ring = &enet->rx_ring;
+	struct device *dev = enet->dev;
+	int size;
+
+	size = rx_ring->length * sizeof(struct bcm4908enet_dma_ring_bd);
+	if (rx_ring->cpu_addr)
+		dma_free_coherent(dev, size, rx_ring->cpu_addr, rx_ring->dma_addr);
+	kfree(rx_ring->slots);
+
+	size = tx_ring->length * sizeof(struct bcm4908enet_dma_ring_bd);
+	if (tx_ring->cpu_addr)
+		dma_free_coherent(dev, size, tx_ring->cpu_addr, tx_ring->dma_addr);
+	kfree(tx_ring->slots);
+}
+
+static int bcm4908enet_dma_alloc(struct bcm4908enet *enet)
+{
+	struct bcm4908enet_dma_ring *tx_ring = &enet->tx_ring;
+	struct bcm4908enet_dma_ring *rx_ring = &enet->rx_ring;
+	struct device *dev = enet->dev;
+	int err;
+
+	tx_ring->length = ENET_TX_BDS_NUM;
+	tx_ring->is_tx = 1;
+	tx_ring->cfg_block = ENET_DMA_CH_TX_CFG;
+	tx_ring->st_ram_block = ENET_DMA_CH_TX_STATE_RAM;
+	err = bcm4908_dma_alloc_buf_descs(enet, tx_ring);
+	if (err) {
+		dev_err(dev, "Failed to alloc TX buf descriptors: %d\n", err);
+		return err;
+	}
+
+	rx_ring->length = ENET_RX_BDS_NUM;
+	rx_ring->is_tx = 0;
+	rx_ring->cfg_block = ENET_DMA_CH_RX_CFG;
+	rx_ring->st_ram_block = ENET_DMA_CH_RX_STATE_RAM;
+	err = bcm4908_dma_alloc_buf_descs(enet, rx_ring);
+	if (err) {
+		dev_err(dev, "Failed to alloc RX buf descriptors: %d\n", err);
+		bcm4908enet_dma_free(enet);
+		return err;
+	}
+
+	return 0;
+}
+
+static void bcm4908enet_dma_reset(struct bcm4908enet *enet)
+{
+	struct bcm4908enet_dma_ring *rings[] = { &enet->rx_ring, &enet->tx_ring };
+	int i;
+
+	/* Disable the DMA controller and channel */
+	for (i = 0; i < ARRAY_SIZE(rings); i++)
+		enet_write(enet, rings[i]->cfg_block + ENET_DMA_CH_CFG, 0);
+	enet_maskset(enet, ENET_DMA_CONTROLLER_CFG, ENET_DMA_CTRL_CFG_MASTER_EN, 0);
+
+	/* Reset channels state */
+	for (i = 0; i < ARRAY_SIZE(rings); i++) {
+		struct bcm4908enet_dma_ring *ring = rings[i];
+
+		enet_write(enet, ring->st_ram_block + ENET_DMA_CH_STATE_RAM_BASE_DESC_PTR, 0);
+		enet_write(enet, ring->st_ram_block + ENET_DMA_CH_STATE_RAM_STATE_DATA, 0);
+		enet_write(enet, ring->st_ram_block + ENET_DMA_CH_STATE_RAM_DESC_LEN_STATUS, 0);
+		enet_write(enet, ring->st_ram_block + ENET_DMA_CH_STATE_RAM_DESC_BASE_BUFPTR, 0);
+	}
+}
+
+static int bcm4908enet_dma_alloc_rx_buf(struct bcm4908enet *enet, unsigned int idx)
+{
+	struct bcm4908enet_dma_ring_bd *buf_desc = &enet->rx_ring.buf_desc[idx];
+	struct bcm4908enet_dma_ring_slot *slot = &enet->rx_ring.slots[idx];
+	struct device *dev = enet->dev;
+	u32 tmp;
+	int err;
+
+	slot->len = ENET_MTU_MAX + ENET_MTU_MAX_EXTRA_SIZE;
+
+	slot->skb = netdev_alloc_skb(enet->netdev, slot->len);
+	if (!slot->skb)
+		return -ENOMEM;
+
+	slot->dma_addr = dma_map_single(dev, slot->skb->data, slot->len, DMA_FROM_DEVICE);
+	err = dma_mapping_error(dev, slot->dma_addr);
+	if (err) {
+		dev_err(dev, "Failed to map DMA buffer: %d\n", err);
+		kfree_skb(slot->skb);
+		slot->skb = NULL;
+		return err;
+	}
+
+	tmp = slot->len << DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT;
+	tmp |= DMA_CTL_STATUS_OWN;
+	if (idx == enet->rx_ring.length - 1)
+		tmp |= DMA_CTL_STATUS_WRAP;
+	buf_desc->ctl = cpu_to_le32(tmp);
+	buf_desc->addr = cpu_to_le32(slot->dma_addr);
+
+	return 0;
+}
+
+static void bcm4908enet_dma_ring_init(struct bcm4908enet *enet,
+				      struct bcm4908enet_dma_ring *ring)
+{
+	int reset_channel = 0; /* We support only 1 main channel (with TX and RX) */
+	int reset_subch = ring->is_tx ? 1 : 0;
+
+	/* Reset the DMA channel */
+	enet_write(enet, ENET_DMA_CTRL_CHANNEL_RESET, BIT(reset_channel * 2 + reset_subch));
+	enet_write(enet, ENET_DMA_CTRL_CHANNEL_RESET, 0);
+
+	enet_write(enet, ring->cfg_block + ENET_DMA_CH_CFG, 0);
+	enet_write(enet, ring->cfg_block + ENET_DMA_CH_CFG_MAX_BURST, ENET_DMA_MAX_BURST_LEN);
+	enet_write(enet, ring->cfg_block + ENET_DMA_CH_CFG_INT_MASK, 0);
+
+	enet_write(enet, ring->st_ram_block + ENET_DMA_CH_STATE_RAM_BASE_DESC_PTR,
+		   (uint32_t)ring->dma_addr);
+}
+
+static void bcm4908enet_dma_uninit(struct bcm4908enet *enet)
+{
+	struct bcm4908enet_dma_ring *rx_ring = &enet->rx_ring;
+	struct bcm4908enet_dma_ring_slot *slot;
+	struct device *dev = enet->dev;
+	int i;
+
+	for (i = rx_ring->length - 1; i >= 0; i--) {
+		slot = &rx_ring->slots[i];
+		if (!slot->skb)
+			continue;
+		dma_unmap_single(dev, slot->dma_addr, slot->len, DMA_FROM_DEVICE);
+		kfree_skb(slot->skb);
+		slot->skb = NULL;
+	}
+}
+
+static int bcm4908enet_dma_init(struct bcm4908enet *enet)
+{
+	struct bcm4908enet_dma_ring *rx_ring = &enet->rx_ring;
+	struct device *dev = enet->dev;
+	int err;
+	int i;
+
+	for (i = 0; i < rx_ring->length; i++) {
+		err = bcm4908enet_dma_alloc_rx_buf(enet, i);
+		if (err) {
+			dev_err(dev, "Failed to alloc RX buffer: %d\n", err);
+			bcm4908enet_dma_uninit(enet);
+			return err;
+		}
+	}
+
+	bcm4908enet_dma_ring_init(enet, &enet->tx_ring);
+	bcm4908enet_dma_ring_init(enet, &enet->rx_ring);
+
+	return 0;
+}
+
+static void bcm4908enet_dma_tx_ring_ensable(struct bcm4908enet *enet,
+					    struct bcm4908enet_dma_ring *ring)
+{
+	enet_write(enet, ring->cfg_block + ENET_DMA_CH_CFG, ENET_DMA_CH_CFG_ENABLE);
+}
+
+static void bcm4908enet_dma_tx_ring_disable(struct bcm4908enet *enet,
+					    struct bcm4908enet_dma_ring *ring)
+{
+	enet_write(enet, ring->cfg_block + ENET_DMA_CH_CFG, 0);
+}
+
+static void bcm4908enet_dma_rx_ring_enable(struct bcm4908enet *enet,
+					   struct bcm4908enet_dma_ring *ring)
+{
+	enet_set(enet, ring->cfg_block + ENET_DMA_CH_CFG, ENET_DMA_CH_CFG_ENABLE);
+}
+
+static void bcm4908enet_dma_rx_ring_disable(struct bcm4908enet *enet,
+					    struct bcm4908enet_dma_ring *ring)
+{
+	unsigned long deadline;
+	u32 tmp;
+
+	enet_maskset(enet, ring->cfg_block + ENET_DMA_CH_CFG, ENET_DMA_CH_CFG_ENABLE, 0);
+
+	deadline = jiffies + usecs_to_jiffies(2000);
+	do {
+		tmp = enet_read(enet, ring->cfg_block + ENET_DMA_CH_CFG);
+		if (!(tmp & ENET_DMA_CH_CFG_ENABLE))
+			return;
+		enet_maskset(enet, ring->cfg_block + ENET_DMA_CH_CFG, ENET_DMA_CH_CFG_ENABLE, 0);
+		usleep_range(10, 30);
+	} while (!time_after_eq(jiffies, deadline));
+
+	dev_warn(enet->dev, "Timeout waiting for DMA TX stop\n");
+}
+
+/***
+ * Ethernet driver
+ */
+
+static void bcm4908enet_gmac_init(struct bcm4908enet *enet)
+{
+	u32 cmd;
+
+	cmd = enet_umac_read(enet, UMAC_CMD);
+	enet_umac_write(enet, UMAC_CMD, cmd | CMD_SW_RESET);
+	enet_umac_write(enet, UMAC_CMD, cmd & ~CMD_SW_RESET);
+
+	enet_set(enet, ENET_FLUSH, ENET_FLUSH_RXFIFO_FLUSH | ENET_FLUSH_TXFIFO_FLUSH);
+	enet_maskset(enet, ENET_FLUSH, ENET_FLUSH_RXFIFO_FLUSH | ENET_FLUSH_TXFIFO_FLUSH, 0);
+
+	enet_set(enet, ENET_MIB_CTRL, ENET_MIB_CTRL_CLR_MIB);
+	enet_maskset(enet, ENET_MIB_CTRL, ENET_MIB_CTRL_CLR_MIB, 0);
+
+	cmd = enet_umac_read(enet, UMAC_CMD);
+	cmd &= ~(CMD_SPEED_MASK << CMD_SPEED_SHIFT);
+	cmd &= ~CMD_TX_EN;
+	cmd &= ~CMD_RX_EN;
+	cmd |= CMD_SPEED_1000 << CMD_SPEED_SHIFT;
+	enet_umac_write(enet, UMAC_CMD, cmd);
+
+	enet_maskset(enet, ENET_GMAC_STATUS,
+		     ENET_GMAC_STATUS_ETH_SPEED_MASK |
+		     ENET_GMAC_STATUS_HD |
+		     ENET_GMAC_STATUS_AUTO_CFG_EN |
+		     ENET_GMAC_STATUS_LINK_UP,
+		     ENET_GMAC_STATUS_ETH_SPEED_1000 |
+		     ENET_GMAC_STATUS_AUTO_CFG_EN |
+		     ENET_GMAC_STATUS_LINK_UP);
+}
+
+static irqreturn_t bcm4908enet_irq_handler(int irq, void *dev_id)
+{
+	struct bcm4908enet *enet = dev_id;
+
+	bcm4908enet_intrs_off(enet);
+	bcm4908enet_intrs_ack(enet);
+
+	napi_schedule(&enet->napi);
+
+	return IRQ_HANDLED;
+}
+
+static int bcm4908enet_open(struct net_device *netdev)
+{
+	struct bcm4908enet *enet = netdev_priv(netdev);
+	struct device *dev = enet->dev;
+	int err;
+
+	err = request_irq(netdev->irq, bcm4908enet_irq_handler, 0, "enet", enet);
+	if (err) {
+		dev_err(dev, "Failed to request IRQ %d: %d\n", netdev->irq, err);
+		return err;
+	}
+
+	bcm4908enet_gmac_init(enet);
+	bcm4908enet_dma_reset(enet);
+	bcm4908enet_dma_init(enet);
+
+	enet_umac_set(enet, UMAC_CMD, CMD_TX_EN | CMD_RX_EN);
+
+	enet_set(enet, ENET_DMA_CONTROLLER_CFG, ENET_DMA_CTRL_CFG_MASTER_EN);
+	enet_maskset(enet, ENET_DMA_CONTROLLER_CFG, ENET_DMA_CTRL_CFG_FLOWC_CH1_EN, 0);
+	bcm4908enet_dma_rx_ring_enable(enet, &enet->rx_ring);
+
+	napi_enable(&enet->napi);
+	netif_carrier_on(netdev);
+	netif_start_queue(netdev);
+
+	bcm4908enet_intrs_ack(enet);
+	bcm4908enet_intrs_on(enet);
+
+	return 0;
+}
+
+static int bcm4908enet_stop(struct net_device *netdev)
+{
+	struct bcm4908enet *enet = netdev_priv(netdev);
+
+	netif_stop_queue(netdev);
+	netif_carrier_off(netdev);
+	napi_disable(&enet->napi);
+
+	bcm4908enet_dma_rx_ring_disable(enet, &enet->rx_ring);
+	bcm4908enet_dma_tx_ring_disable(enet, &enet->tx_ring);
+
+	bcm4908enet_dma_uninit(enet);
+
+	free_irq(enet->netdev->irq, enet);
+
+	return 0;
+}
+
+static int bcm4908enet_start_xmit(struct sk_buff *skb, struct net_device *netdev)
+{
+	struct bcm4908enet *enet = netdev_priv(netdev);
+	struct bcm4908enet_dma_ring *ring = &enet->tx_ring;
+	struct bcm4908enet_dma_ring_slot *slot;
+	struct device *dev = enet->dev;
+	struct bcm4908enet_dma_ring_bd *buf_desc;
+	int free_buf_descs;
+	u32 tmp;
+
+	/* Free transmitted skbs */
+	while (ring->read_idx != ring->write_idx) {
+		buf_desc = &ring->buf_desc[ring->read_idx];
+		if (buf_desc->ctl & DMA_CTL_STATUS_OWN)
+			break;
+		slot = &ring->slots[ring->read_idx];
+
+		dma_unmap_single(dev, slot->dma_addr, slot->len, DMA_TO_DEVICE);
+		dev_kfree_skb(slot->skb);
+		if (++ring->read_idx == ring->length)
+			ring->read_idx = 0;
+	}
+
+	/* Don't use the last empty buf descriptor */
+	if (ring->read_idx <= ring->write_idx)
+		free_buf_descs = ring->read_idx - ring->write_idx + ring->length;
+	else
+		free_buf_descs = ring->read_idx - ring->write_idx;
+	if (free_buf_descs < 2)
+		return NETDEV_TX_BUSY;
+
+	/* Hardware removes OWN bit after sending data */
+	buf_desc = &ring->buf_desc[ring->write_idx];
+	if (unlikely(le32_to_cpu(buf_desc->ctl) & DMA_CTL_STATUS_OWN)) {
+		netif_stop_queue(netdev);
+		return NETDEV_TX_BUSY;
+	}
+
+	slot = &ring->slots[ring->write_idx];
+	slot->skb = skb;
+	slot->len = skb->len;
+	slot->dma_addr = dma_map_single(dev, skb->data, skb->len, DMA_TO_DEVICE);
+	if (unlikely(dma_mapping_error(dev, slot->dma_addr)))
+		return NETDEV_TX_BUSY;
+
+	tmp = skb->len << DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT;
+	tmp |= DMA_CTL_STATUS_OWN;
+	tmp |= DMA_CTL_STATUS_SOP;
+	tmp |= DMA_CTL_STATUS_EOP;
+	tmp |= DMA_CTL_STATUS_APPEND_CRC;
+	if (ring->write_idx + 1 == ring->length - 1)
+		tmp |= DMA_CTL_STATUS_WRAP;
+
+	buf_desc->addr = cpu_to_le32((uint32_t)slot->dma_addr);
+	buf_desc->ctl = cpu_to_le32(tmp);
+
+	bcm4908enet_dma_tx_ring_ensable(enet, &enet->tx_ring);
+
+	if (++ring->write_idx == ring->length - 1)
+		ring->write_idx = 0;
+	enet->netdev->stats.tx_bytes += skb->len;
+	enet->netdev->stats.tx_packets++;
+
+	return NETDEV_TX_OK;
+}
+
+static int bcm4908enet_poll(struct napi_struct *napi, int weight)
+{
+	struct bcm4908enet *enet = container_of(napi, struct bcm4908enet, napi);
+	struct device *dev = enet->dev;
+	int handled = 0;
+
+	while (handled < weight) {
+		struct bcm4908enet_dma_ring_bd *buf_desc;
+		struct bcm4908enet_dma_ring_slot slot;
+		u32 ctl;
+		int len;
+		int err;
+
+		buf_desc = &enet->rx_ring.buf_desc[enet->rx_ring.read_idx];
+		ctl = le32_to_cpu(buf_desc->ctl);
+		if (ctl & DMA_CTL_STATUS_OWN)
+			break;
+
+		slot = enet->rx_ring.slots[enet->rx_ring.read_idx];
+
+		/* Provide new buffer before unpinning the old one */
+		err = bcm4908enet_dma_alloc_rx_buf(enet, enet->rx_ring.read_idx);
+		if (err)
+			break;
+
+		if (++enet->rx_ring.read_idx == enet->rx_ring.length)
+			enet->rx_ring.read_idx = 0;
+
+		len = (ctl & DMA_CTL_LEN_DESC_BUFLENGTH) >> DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT;
+
+		if (len < ENET_MTU_MIN ||
+		    (ctl & (DMA_CTL_STATUS_SOP | DMA_CTL_STATUS_EOP)) != (DMA_CTL_STATUS_SOP | DMA_CTL_STATUS_EOP)) {
+			enet->netdev->stats.rx_dropped++;
+			break;
+		}
+
+		dma_unmap_single(dev, slot.dma_addr, slot.len, DMA_FROM_DEVICE);
+
+		skb_put(slot.skb, len - 4 + 2);
+		slot.skb->protocol = eth_type_trans(slot.skb, enet->netdev);
+		netif_receive_skb(slot.skb);
+
+		enet->netdev->stats.rx_packets++;
+		enet->netdev->stats.rx_bytes += len;
+	}
+
+	if (handled < weight) {
+		napi_complete_done(napi, handled);
+		bcm4908enet_intrs_on(enet);
+	}
+
+	return handled;
+}
+
+static const struct net_device_ops bcm96xx_netdev_ops = {
+	.ndo_open = bcm4908enet_open,
+	.ndo_stop = bcm4908enet_stop,
+	.ndo_start_xmit = bcm4908enet_start_xmit,
+	.ndo_set_mac_address = eth_mac_addr,
+};
+
+static int bcm4908enet_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct net_device *netdev;
+	struct bcm4908enet *enet;
+	int err;
+
+	netdev = devm_alloc_etherdev(dev, sizeof(*enet));
+	if (!netdev)
+		return -ENOMEM;
+
+	enet = netdev_priv(netdev);
+	enet->dev = dev;
+	enet->netdev = netdev;
+
+	enet->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(enet->base)) {
+		dev_err(dev, "Failed to map registers: %ld\n", PTR_ERR(enet->base));
+		return PTR_ERR(enet->base);
+	}
+
+	netdev->irq = platform_get_irq_byname(pdev, "rx");
+	if (netdev->irq < 0)
+		return netdev->irq;
+
+	dma_set_coherent_mask(dev, DMA_BIT_MASK(32));
+
+	err = bcm4908enet_dma_alloc(enet);
+	if (err)
+		return err;
+
+	SET_NETDEV_DEV(netdev, &pdev->dev);
+	eth_hw_addr_random(netdev);
+	netdev->netdev_ops = &bcm96xx_netdev_ops;
+	netdev->min_mtu = ETH_ZLEN;
+	netdev->mtu = ENET_MTU_MAX;
+	netdev->max_mtu = ENET_MTU_MAX;
+	netif_napi_add(netdev, &enet->napi, bcm4908enet_poll, 64);
+
+	err = register_netdev(netdev);
+	if (err) {
+		bcm4908enet_dma_free(enet);
+		return err;
+	}
+
+	platform_set_drvdata(pdev, enet);
+
+	return 0;
+}
+
+static int bcm4908enet_remove(struct platform_device *pdev)
+{
+	struct bcm4908enet *enet = platform_get_drvdata(pdev);
+
+	unregister_netdev(enet->netdev);
+	netif_napi_del(&enet->napi);
+	bcm4908enet_dma_free(enet);
+
+	return 0;
+}
+
+static const struct of_device_id bcm4908enet_of_match[] = {
+	{ .compatible = "brcm,bcm4908enet"},
+	{},
+};
+
+static struct platform_driver bcm4908enet_driver = {
+	.driver = {
+		.name = "bcm4908enet",
+		.of_match_table = bcm4908enet_of_match,
+	},
+	.probe	= bcm4908enet_probe,
+	.remove = bcm4908enet_remove,
+};
+module_platform_driver(bcm4908enet_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DEVICE_TABLE(of, bcm4908enet_of_match);

drivers/net/ethernet/broadcom/bcm4908enet.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __BCM4908ENET_H
+#define __BCM4908ENET_H
+
+#define ENET_CONTROL					0x000
+#define ENET_MIB_CTRL					0x004
+#define  ENET_MIB_CTRL_CLR_MIB				0x00000001
+#define ENET_RX_ERR_MASK				0x008
+#define ENET_MIB_MAX_PKT_SIZE				0x00C
+#define  ENET_MIB_MAX_PKT_SIZE_VAL			0x00003fff
+#define ENET_DIAG_OUT					0x01c
+#define ENET_ENABLE_DROP_PKT				0x020
+#define ENET_IRQ_ENABLE					0x024
+#define  ENET_IRQ_ENABLE_OVFL				0x00000001
+#define ENET_GMAC_STATUS				0x028
+#define  ENET_GMAC_STATUS_ETH_SPEED_MASK		0x00000003
+#define  ENET_GMAC_STATUS_ETH_SPEED_10			0x00000000
+#define  ENET_GMAC_STATUS_ETH_SPEED_100			0x00000001
+#define  ENET_GMAC_STATUS_ETH_SPEED_1000		0x00000002
+#define  ENET_GMAC_STATUS_HD				0x00000004
+#define  ENET_GMAC_STATUS_AUTO_CFG_EN			0x00000008
+#define  ENET_GMAC_STATUS_LINK_UP			0x00000010
+#define ENET_IRQ_STATUS					0x02c
+#define  ENET_IRQ_STATUS_OVFL				0x00000001
+#define ENET_OVERFLOW_COUNTER				0x030
+#define ENET_FLUSH					0x034
+#define  ENET_FLUSH_RXFIFO_FLUSH			0x00000001
+#define  ENET_FLUSH_TXFIFO_FLUSH			0x00000002
+#define ENET_RSV_SELECT					0x038
+#define ENET_BP_FORCE					0x03c
+#define  ENET_BP_FORCE_FORCE				0x00000001
+#define ENET_DMA_RX_OK_TO_SEND_COUNT			0x040
+#define  ENET_DMA_RX_OK_TO_SEND_COUNT_VAL		0x0000000f
+#define ENET_TX_CRC_CTRL				0x044
+#define ENET_MIB					0x200
+#define ENET_UNIMAC					0x400
+#define ENET_DMA					0x800
+#define ENET_DMA_CONTROLLER_CFG				0x800
+#define  ENET_DMA_CTRL_CFG_MASTER_EN			0x00000001
+#define  ENET_DMA_CTRL_CFG_FLOWC_CH1_EN			0x00000002
+#define  ENET_DMA_CTRL_CFG_FLOWC_CH3_EN			0x00000004
+#define ENET_DMA_FLOWCTL_CH1_THRESH_LO			0x804
+#define ENET_DMA_FLOWCTL_CH1_THRESH_HI			0x808
+#define ENET_DMA_FLOWCTL_CH1_ALLOC			0x80c
+#define  ENET_DMA_FLOWCTL_CH1_ALLOC_FORCE		0x80000000
+#define ENET_DMA_FLOWCTL_CH3_THRESH_LO			0x810
+#define ENET_DMA_FLOWCTL_CH3_THRESH_HI			0x814
+#define ENET_DMA_FLOWCTL_CH3_ALLOC			0x818
+#define ENET_DMA_FLOWCTL_CH5_THRESH_LO			0x81C
+#define ENET_DMA_FLOWCTL_CH5_THRESH_HI			0x820
+#define ENET_DMA_FLOWCTL_CH5_ALLOC			0x824
+#define ENET_DMA_FLOWCTL_CH7_THRESH_LO			0x828
+#define ENET_DMA_FLOWCTL_CH7_THRESH_HI			0x82C
+#define ENET_DMA_FLOWCTL_CH7_ALLOC			0x830
+#define ENET_DMA_CTRL_CHANNEL_RESET			0x834
+#define ENET_DMA_CTRL_CHANNEL_DEBUG			0x838
+#define ENET_DMA_CTRL_GLOBAL_INTERRUPT_STATUS		0x840
+#define ENET_DMA_CTRL_GLOBAL_INTERRUPT_MASK		0x844
+#define ENET_DMA_CH0_CFG				0xa00		/* RX */
+#define ENET_DMA_CH1_CFG				0xa10		/* TX */
+#define ENET_DMA_CH0_STATE_RAM				0xc00		/* RX */
+#define ENET_DMA_CH1_STATE_RAM				0xc10		/* TX */
+
+#define ENET_DMA_CH_CFG					0x00		/* assorted configuration */
+#define  ENET_DMA_CH_CFG_ENABLE				0x00000001	/* set to enable channel */
+#define  ENET_DMA_CH_CFG_PKT_HALT			0x00000002	/* idle after an EOP flag is detected */
+#define  ENET_DMA_CH_CFG_BURST_HALT			0x00000004	/* idle after finish current memory burst */
+#define ENET_DMA_CH_CFG_INT_STAT			0x04		/* interrupts control and status */
+#define ENET_DMA_CH_CFG_INT_MASK			0x08		/* interrupts mask */
+#define  ENET_DMA_CH_CFG_INT_BUFF_DONE			0x00000001	/* buffer done */
+#define  ENET_DMA_CH_CFG_INT_DONE			0x00000002	/* packet xfer complete */
+#define  ENET_DMA_CH_CFG_INT_NO_DESC			0x00000004	/* no valid descriptors */
+#define  ENET_DMA_CH_CFG_INT_RX_ERROR			0x00000008	/* rxdma detect client protocol error */
+#define ENET_DMA_CH_CFG_MAX_BURST			0x0c		/* max burst length permitted */
+#define  ENET_DMA_CH_CFG_MAX_BURST_DESCSIZE_SEL		0x00040000	/* DMA Descriptor Size Selection */
+#define ENET_DMA_CH_CFG_SIZE				0x10
+
+#define ENET_DMA_CH_STATE_RAM_BASE_DESC_PTR		0x00		/* descriptor ring start address */
+#define ENET_DMA_CH_STATE_RAM_STATE_DATA		0x04		/* state/bytes done/ring offset */
+#define ENET_DMA_CH_STATE_RAM_DESC_LEN_STATUS		0x08		/* buffer descriptor status and len */
+#define ENET_DMA_CH_STATE_RAM_DESC_BASE_BUFPTR		0x0c		/* buffer descrpitor current processing */
+#define ENET_DMA_CH_STATE_RAM_SIZE			0x10
+
+#define DMA_CTL_STATUS_APPEND_CRC			0x00000100
+#define DMA_CTL_STATUS_APPEND_BRCM_TAG			0x00000200
+#define DMA_CTL_STATUS_PRIO				0x00000C00  /* Prio for Tx */
+#define DMA_CTL_STATUS_WRAP				0x00001000  /* */
+#define DMA_CTL_STATUS_SOP				0x00002000  /* first buffer in packet */
+#define DMA_CTL_STATUS_EOP				0x00004000  /* last buffer in packet */
+#define DMA_CTL_STATUS_OWN				0x00008000  /* cleared by DMA, set by SW */
+#define DMA_CTL_LEN_DESC_BUFLENGTH			0x0fff0000
+#define DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT		16
+#define DMA_CTL_LEN_DESC_MULTICAST			0x40000000
+#define DMA_CTL_LEN_DESC_USEFPM				0x80000000
+
+#endif