WIP FPC-III support

[linux/fpc-iii.git] / drivers / net / ethernet / arc / emac_main.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2004-2013 Synopsys, Inc. (www.synopsys.com)
 *
 * Driver for the ARC EMAC 10100 (hardware revision 5)
 *
 * Contributors:
 *              Amit Bhor
 *              Sameer Dhavale
 *              Vineet Gupta
 */

#include <linux/crc32.h>
#include <linux/etherdevice.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/of_mdio.h>
#include <linux/of_net.h>
#include <linux/of_platform.h>

#include "emac.h"

static void arc_emac_restart(struct net_device *ndev);

/**
 * arc_emac_tx_avail - Return the number of available slots in the tx ring.
 * @priv: Pointer to ARC EMAC private data structure.
 *
 * returns: the number of slots available for transmission in tx the ring.
 */
static inline int arc_emac_tx_avail(struct arc_emac_priv *priv)
{
        return (priv->txbd_dirty + TX_BD_NUM - priv->txbd_curr - 1) % TX_BD_NUM;
}

/**
 * arc_emac_adjust_link - Adjust the PHY link duplex.
 * @ndev:       Pointer to the net_device structure.
 *
 * This function is called to change the duplex setting after auto negotiation
 * is done by the PHY.
 */
static void arc_emac_adjust_link(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        struct phy_device *phy_dev = ndev->phydev;
        unsigned int reg, state_changed = 0;

        if (priv->link != phy_dev->link) {
                priv->link = phy_dev->link;
                state_changed = 1;
        }

        if (priv->speed != phy_dev->speed) {
                priv->speed = phy_dev->speed;
                state_changed = 1;
                if (priv->set_mac_speed)
                        priv->set_mac_speed(priv, priv->speed);
        }

        if (priv->duplex != phy_dev->duplex) {
                reg = arc_reg_get(priv, R_CTRL);

                if (phy_dev->duplex == DUPLEX_FULL)
                        reg |= ENFL_MASK;
                else
                        reg &= ~ENFL_MASK;

                arc_reg_set(priv, R_CTRL, reg);
                priv->duplex = phy_dev->duplex;
                state_changed = 1;
        }

        if (state_changed)
                phy_print_status(phy_dev);
}

/**
 * arc_emac_get_drvinfo - Get EMAC driver information.
 * @ndev:       Pointer to net_device structure.
 * @info:       Pointer to ethtool_drvinfo structure.
 *
 * This implements ethtool command for getting the driver information.
 * Issue "ethtool -i ethX" under linux prompt to execute this function.
 */
static void arc_emac_get_drvinfo(struct net_device *ndev,
                                 struct ethtool_drvinfo *info)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);

        strlcpy(info->driver, priv->drv_name, sizeof(info->driver));
}

static const struct ethtool_ops arc_emac_ethtool_ops = {
        .get_drvinfo    = arc_emac_get_drvinfo,
        .get_link       = ethtool_op_get_link,
        .get_link_ksettings = phy_ethtool_get_link_ksettings,
        .set_link_ksettings = phy_ethtool_set_link_ksettings,
};

#define FIRST_OR_LAST_MASK      (FIRST_MASK | LAST_MASK)

/**
 * arc_emac_tx_clean - clears processed by EMAC Tx BDs.
 * @ndev:       Pointer to the network device.
 */
static void arc_emac_tx_clean(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        unsigned int i;

        for (i = 0; i < TX_BD_NUM; i++) {
                unsigned int *txbd_dirty = &priv->txbd_dirty;
                struct arc_emac_bd *txbd = &priv->txbd[*txbd_dirty];
                struct buffer_state *tx_buff = &priv->tx_buff[*txbd_dirty];
                struct sk_buff *skb = tx_buff->skb;
                unsigned int info = le32_to_cpu(txbd->info);

                if ((info & FOR_EMAC) || !txbd->data || !skb)
                        break;

                if (unlikely(info & (DROP | DEFR | LTCL | UFLO))) {
                        stats->tx_errors++;
                        stats->tx_dropped++;

                        if (info & DEFR)
                                stats->tx_carrier_errors++;

                        if (info & LTCL)
                                stats->collisions++;

                        if (info & UFLO)
                                stats->tx_fifo_errors++;
                } else if (likely(info & FIRST_OR_LAST_MASK)) {
                        stats->tx_packets++;
                        stats->tx_bytes += skb->len;
                }

                dma_unmap_single(&ndev->dev, dma_unmap_addr(tx_buff, addr),
                                 dma_unmap_len(tx_buff, len), DMA_TO_DEVICE);

                /* return the sk_buff to system */
                dev_consume_skb_irq(skb);

                txbd->data = 0;
                txbd->info = 0;
                tx_buff->skb = NULL;

                *txbd_dirty = (*txbd_dirty + 1) % TX_BD_NUM;
        }

        /* Ensure that txbd_dirty is visible to tx() before checking
         * for queue stopped.
         */
        smp_mb();

        if (netif_queue_stopped(ndev) && arc_emac_tx_avail(priv))
                netif_wake_queue(ndev);
}

/**
 * arc_emac_rx - processing of Rx packets.
 * @ndev:       Pointer to the network device.
 * @budget:     How many BDs to process on 1 call.
 *
 * returns:     Number of processed BDs
 *
 * Iterate through Rx BDs and deliver received packages to upper layer.
 */
static int arc_emac_rx(struct net_device *ndev, int budget)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        unsigned int work_done;

        for (work_done = 0; work_done < budget; work_done++) {
                unsigned int *last_rx_bd = &priv->last_rx_bd;
                struct net_device_stats *stats = &ndev->stats;
                struct buffer_state *rx_buff = &priv->rx_buff[*last_rx_bd];
                struct arc_emac_bd *rxbd = &priv->rxbd[*last_rx_bd];
                unsigned int pktlen, info = le32_to_cpu(rxbd->info);
                struct sk_buff *skb;
                dma_addr_t addr;

                if (unlikely((info & OWN_MASK) == FOR_EMAC))
                        break;

                /* Make a note that we saw a packet at this BD.
                 * So next time, driver starts from this + 1
                 */
                *last_rx_bd = (*last_rx_bd + 1) % RX_BD_NUM;

                if (unlikely((info & FIRST_OR_LAST_MASK) !=
                             FIRST_OR_LAST_MASK)) {
                        /* We pre-allocate buffers of MTU size so incoming
                         * packets won't be split/chained.
                         */
                        if (net_ratelimit())
                                netdev_err(ndev, "incomplete packet received\n");

                        /* Return ownership to EMAC */
                        rxbd->info = cpu_to_le32(FOR_EMAC | EMAC_BUFFER_SIZE);
                        stats->rx_errors++;
                        stats->rx_length_errors++;
                        continue;
                }

                /* Prepare the BD for next cycle. netif_receive_skb()
                 * only if new skb was allocated and mapped to avoid holes
                 * in the RX fifo.
                 */
                skb = netdev_alloc_skb_ip_align(ndev, EMAC_BUFFER_SIZE);
                if (unlikely(!skb)) {
                        if (net_ratelimit())
                                netdev_err(ndev, "cannot allocate skb\n");
                        /* Return ownership to EMAC */
                        rxbd->info = cpu_to_le32(FOR_EMAC | EMAC_BUFFER_SIZE);
                        stats->rx_errors++;
                        stats->rx_dropped++;
                        continue;
                }

                addr = dma_map_single(&ndev->dev, (void *)skb->data,
                                      EMAC_BUFFER_SIZE, DMA_FROM_DEVICE);
                if (dma_mapping_error(&ndev->dev, addr)) {
                        if (net_ratelimit())
                                netdev_err(ndev, "cannot map dma buffer\n");
                        dev_kfree_skb(skb);
                        /* Return ownership to EMAC */
                        rxbd->info = cpu_to_le32(FOR_EMAC | EMAC_BUFFER_SIZE);
                        stats->rx_errors++;
                        stats->rx_dropped++;
                        continue;
                }

                /* unmap previosly mapped skb */
                dma_unmap_single(&ndev->dev, dma_unmap_addr(rx_buff, addr),
                                 dma_unmap_len(rx_buff, len), DMA_FROM_DEVICE);

                pktlen = info & LEN_MASK;
                stats->rx_packets++;
                stats->rx_bytes += pktlen;
                skb_put(rx_buff->skb, pktlen);
                rx_buff->skb->dev = ndev;
                rx_buff->skb->protocol = eth_type_trans(rx_buff->skb, ndev);

                netif_receive_skb(rx_buff->skb);

                rx_buff->skb = skb;
                dma_unmap_addr_set(rx_buff, addr, addr);
                dma_unmap_len_set(rx_buff, len, EMAC_BUFFER_SIZE);

                rxbd->data = cpu_to_le32(addr);

                /* Make sure pointer to data buffer is set */
                wmb();

                /* Return ownership to EMAC */
                rxbd->info = cpu_to_le32(FOR_EMAC | EMAC_BUFFER_SIZE);
        }

        return work_done;
}

/**
 * arc_emac_rx_miss_handle - handle R_MISS register
 * @ndev:       Pointer to the net_device structure.
 */
static void arc_emac_rx_miss_handle(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        unsigned int miss;

        miss = arc_reg_get(priv, R_MISS);
        if (miss) {
                stats->rx_errors += miss;
                stats->rx_missed_errors += miss;
                priv->rx_missed_errors += miss;
        }
}

/**
 * arc_emac_rx_stall_check - check RX stall
 * @ndev:       Pointer to the net_device structure.
 * @budget:     How many BDs requested to process on 1 call.
 * @work_done:  How many BDs processed
 *
 * Under certain conditions EMAC stop reception of incoming packets and
 * continuously increment R_MISS register instead of saving data into
 * provided buffer. This function detect that condition and restart
 * EMAC.
 */
static void arc_emac_rx_stall_check(struct net_device *ndev,
                                    int budget, unsigned int work_done)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        struct arc_emac_bd *rxbd;

        if (work_done)
                priv->rx_missed_errors = 0;

        if (priv->rx_missed_errors && budget) {
                rxbd = &priv->rxbd[priv->last_rx_bd];
                if (le32_to_cpu(rxbd->info) & FOR_EMAC) {
                        arc_emac_restart(ndev);
                        priv->rx_missed_errors = 0;
                }
        }
}

/**
 * arc_emac_poll - NAPI poll handler.
 * @napi:       Pointer to napi_struct structure.
 * @budget:     How many BDs to process on 1 call.
 *
 * returns:     Number of processed BDs
 */
static int arc_emac_poll(struct napi_struct *napi, int budget)
{
        struct net_device *ndev = napi->dev;
        struct arc_emac_priv *priv = netdev_priv(ndev);
        unsigned int work_done;

        arc_emac_tx_clean(ndev);
        arc_emac_rx_miss_handle(ndev);

        work_done = arc_emac_rx(ndev, budget);
        if (work_done < budget) {
                napi_complete_done(napi, work_done);
                arc_reg_or(priv, R_ENABLE, RXINT_MASK | TXINT_MASK);
        }

        arc_emac_rx_stall_check(ndev, budget, work_done);

        return work_done;
}

/**
 * arc_emac_intr - Global interrupt handler for EMAC.
 * @irq:                irq number.
 * @dev_instance:       device instance.
 *
 * returns: IRQ_HANDLED for all cases.
 *
 * ARC EMAC has only 1 interrupt line, and depending on bits raised in
 * STATUS register we may tell what is a reason for interrupt to fire.
 */
static irqreturn_t arc_emac_intr(int irq, void *dev_instance)
{
        struct net_device *ndev = dev_instance;
        struct arc_emac_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        unsigned int status;

        status = arc_reg_get(priv, R_STATUS);
        status &= ~MDIO_MASK;

        /* Reset all flags except "MDIO complete" */
        arc_reg_set(priv, R_STATUS, status);

        if (status & (RXINT_MASK | TXINT_MASK)) {
                if (likely(napi_schedule_prep(&priv->napi))) {
                        arc_reg_clr(priv, R_ENABLE, RXINT_MASK | TXINT_MASK);
                        __napi_schedule(&priv->napi);
                }
        }

        if (status & ERR_MASK) {
                /* MSER/RXCR/RXFR/RXFL interrupt fires on corresponding
                 * 8-bit error counter overrun.
                 */

                if (status & MSER_MASK) {
                        stats->rx_missed_errors += 0x100;
                        stats->rx_errors += 0x100;
                        priv->rx_missed_errors += 0x100;
                        napi_schedule(&priv->napi);
                }

                if (status & RXCR_MASK) {
                        stats->rx_crc_errors += 0x100;
                        stats->rx_errors += 0x100;
                }

                if (status & RXFR_MASK) {
                        stats->rx_frame_errors += 0x100;
                        stats->rx_errors += 0x100;
                }

                if (status & RXFL_MASK) {
                        stats->rx_over_errors += 0x100;
                        stats->rx_errors += 0x100;
                }
        }

        return IRQ_HANDLED;
}

#ifdef CONFIG_NET_POLL_CONTROLLER
static void arc_emac_poll_controller(struct net_device *dev)
{
        disable_irq(dev->irq);
        arc_emac_intr(dev->irq, dev);
        enable_irq(dev->irq);
}
#endif

/**
 * arc_emac_open - Open the network device.
 * @ndev:       Pointer to the network device.
 *
 * returns: 0, on success or non-zero error value on failure.
 *
 * This function sets the MAC address, requests and enables an IRQ
 * for the EMAC device and starts the Tx queue.
 * It also connects to the phy device.
 */
static int arc_emac_open(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        struct phy_device *phy_dev = ndev->phydev;
        int i;

        phy_dev->autoneg = AUTONEG_ENABLE;
        phy_dev->speed = 0;
        phy_dev->duplex = 0;
        linkmode_and(phy_dev->advertising, phy_dev->advertising,
                     phy_dev->supported);

        priv->last_rx_bd = 0;

        /* Allocate and set buffers for Rx BD's */
        for (i = 0; i < RX_BD_NUM; i++) {
                dma_addr_t addr;
                unsigned int *last_rx_bd = &priv->last_rx_bd;
                struct arc_emac_bd *rxbd = &priv->rxbd[*last_rx_bd];
                struct buffer_state *rx_buff = &priv->rx_buff[*last_rx_bd];

                rx_buff->skb = netdev_alloc_skb_ip_align(ndev,
                                                         EMAC_BUFFER_SIZE);
                if (unlikely(!rx_buff->skb))
                        return -ENOMEM;

                addr = dma_map_single(&ndev->dev, (void *)rx_buff->skb->data,
                                      EMAC_BUFFER_SIZE, DMA_FROM_DEVICE);
                if (dma_mapping_error(&ndev->dev, addr)) {
                        netdev_err(ndev, "cannot dma map\n");
                        dev_kfree_skb(rx_buff->skb);
                        return -ENOMEM;
                }
                dma_unmap_addr_set(rx_buff, addr, addr);
                dma_unmap_len_set(rx_buff, len, EMAC_BUFFER_SIZE);

                rxbd->data = cpu_to_le32(addr);

                /* Make sure pointer to data buffer is set */
                wmb();

                /* Return ownership to EMAC */
                rxbd->info = cpu_to_le32(FOR_EMAC | EMAC_BUFFER_SIZE);

                *last_rx_bd = (*last_rx_bd + 1) % RX_BD_NUM;
        }

        priv->txbd_curr = 0;
        priv->txbd_dirty = 0;

        /* Clean Tx BD's */
        memset(priv->txbd, 0, TX_RING_SZ);

        /* Initialize logical address filter */
        arc_reg_set(priv, R_LAFL, 0);
        arc_reg_set(priv, R_LAFH, 0);

        /* Set BD ring pointers for device side */
        arc_reg_set(priv, R_RX_RING, (unsigned int)priv->rxbd_dma);
        arc_reg_set(priv, R_TX_RING, (unsigned int)priv->txbd_dma);

        /* Enable interrupts */
        arc_reg_set(priv, R_ENABLE, RXINT_MASK | TXINT_MASK | ERR_MASK);

        /* Set CONTROL */
        arc_reg_set(priv, R_CTRL,
                    (RX_BD_NUM << 24) | /* RX BD table length */
                    (TX_BD_NUM << 16) | /* TX BD table length */
                    TXRN_MASK | RXRN_MASK);

        napi_enable(&priv->napi);

        /* Enable EMAC */
        arc_reg_or(priv, R_CTRL, EN_MASK);

        phy_start(ndev->phydev);

        netif_start_queue(ndev);

        return 0;
}

/**
 * arc_emac_set_rx_mode - Change the receive filtering mode.
 * @ndev:       Pointer to the network device.
 *
 * This function enables/disables promiscuous or all-multicast mode
 * and updates the multicast filtering list of the network device.
 */
static void arc_emac_set_rx_mode(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);

        if (ndev->flags & IFF_PROMISC) {
                arc_reg_or(priv, R_CTRL, PROM_MASK);
        } else {
                arc_reg_clr(priv, R_CTRL, PROM_MASK);

                if (ndev->flags & IFF_ALLMULTI) {
                        arc_reg_set(priv, R_LAFL, ~0);
                        arc_reg_set(priv, R_LAFH, ~0);
                } else if (ndev->flags & IFF_MULTICAST) {
                        struct netdev_hw_addr *ha;
                        unsigned int filter[2] = { 0, 0 };
                        int bit;

                        netdev_for_each_mc_addr(ha, ndev) {
                                bit = ether_crc_le(ETH_ALEN, ha->addr) >> 26;
                                filter[bit >> 5] |= 1 << (bit & 31);
                        }

                        arc_reg_set(priv, R_LAFL, filter[0]);
                        arc_reg_set(priv, R_LAFH, filter[1]);
                } else {
                        arc_reg_set(priv, R_LAFL, 0);
                        arc_reg_set(priv, R_LAFH, 0);
                }
        }
}

/**
 * arc_free_tx_queue - free skb from tx queue
 * @ndev:       Pointer to the network device.
 *
 * This function must be called while EMAC disable
 */
static void arc_free_tx_queue(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        unsigned int i;

        for (i = 0; i < TX_BD_NUM; i++) {
                struct arc_emac_bd *txbd = &priv->txbd[i];
                struct buffer_state *tx_buff = &priv->tx_buff[i];

                if (tx_buff->skb) {
                        dma_unmap_single(&ndev->dev,
                                         dma_unmap_addr(tx_buff, addr),
                                         dma_unmap_len(tx_buff, len),
                                         DMA_TO_DEVICE);

                        /* return the sk_buff to system */
                        dev_kfree_skb_irq(tx_buff->skb);
                }

                txbd->info = 0;
                txbd->data = 0;
                tx_buff->skb = NULL;
        }
}

/**
 * arc_free_rx_queue - free skb from rx queue
 * @ndev:       Pointer to the network device.
 *
 * This function must be called while EMAC disable
 */
static void arc_free_rx_queue(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        unsigned int i;

        for (i = 0; i < RX_BD_NUM; i++) {
                struct arc_emac_bd *rxbd = &priv->rxbd[i];
                struct buffer_state *rx_buff = &priv->rx_buff[i];

                if (rx_buff->skb) {
                        dma_unmap_single(&ndev->dev,
                                         dma_unmap_addr(rx_buff, addr),
                                         dma_unmap_len(rx_buff, len),
                                         DMA_FROM_DEVICE);

                        /* return the sk_buff to system */
                        dev_kfree_skb_irq(rx_buff->skb);
                }

                rxbd->info = 0;
                rxbd->data = 0;
                rx_buff->skb = NULL;
        }
}

/**
 * arc_emac_stop - Close the network device.
 * @ndev:       Pointer to the network device.
 *
 * This function stops the Tx queue, disables interrupts and frees the IRQ for
 * the EMAC device.
 * It also disconnects the PHY device associated with the EMAC device.
 */
static int arc_emac_stop(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);

        napi_disable(&priv->napi);
        netif_stop_queue(ndev);

        phy_stop(ndev->phydev);

        /* Disable interrupts */
        arc_reg_clr(priv, R_ENABLE, RXINT_MASK | TXINT_MASK | ERR_MASK);

        /* Disable EMAC */
        arc_reg_clr(priv, R_CTRL, EN_MASK);

        /* Return the sk_buff to system */
        arc_free_tx_queue(ndev);
        arc_free_rx_queue(ndev);

        return 0;
}

/**
 * arc_emac_stats - Get system network statistics.
 * @ndev:       Pointer to net_device structure.
 *
 * Returns the address of the device statistics structure.
 * Statistics are updated in interrupt handler.
 */
static struct net_device_stats *arc_emac_stats(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        unsigned long miss, rxerr;
        u8 rxcrc, rxfram, rxoflow;

        rxerr = arc_reg_get(priv, R_RXERR);
        miss = arc_reg_get(priv, R_MISS);

        rxcrc = rxerr;
        rxfram = rxerr >> 8;
        rxoflow = rxerr >> 16;

        stats->rx_errors += miss;
        stats->rx_errors += rxcrc + rxfram + rxoflow;

        stats->rx_over_errors += rxoflow;
        stats->rx_frame_errors += rxfram;
        stats->rx_crc_errors += rxcrc;
        stats->rx_missed_errors += miss;

        return stats;
}

/**
 * arc_emac_tx - Starts the data transmission.
 * @skb:        sk_buff pointer that contains data to be Transmitted.
 * @ndev:       Pointer to net_device structure.
 *
 * returns: NETDEV_TX_OK, on success
 *              NETDEV_TX_BUSY, if any of the descriptors are not free.
 *
 * This function is invoked from upper layers to initiate transmission.
 */
static netdev_tx_t arc_emac_tx(struct sk_buff *skb, struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        unsigned int len, *txbd_curr = &priv->txbd_curr;
        struct net_device_stats *stats = &ndev->stats;
        __le32 *info = &priv->txbd[*txbd_curr].info;
        dma_addr_t addr;

        if (skb_padto(skb, ETH_ZLEN))
                return NETDEV_TX_OK;

        len = max_t(unsigned int, ETH_ZLEN, skb->len);

        if (unlikely(!arc_emac_tx_avail(priv))) {
                netif_stop_queue(ndev);
                netdev_err(ndev, "BUG! Tx Ring full when queue awake!\n");
                return NETDEV_TX_BUSY;
        }

        addr = dma_map_single(&ndev->dev, (void *)skb->data, len,
                              DMA_TO_DEVICE);

        if (unlikely(dma_mapping_error(&ndev->dev, addr))) {
                stats->tx_dropped++;
                stats->tx_errors++;
                dev_kfree_skb_any(skb);
                return NETDEV_TX_OK;
        }
        dma_unmap_addr_set(&priv->tx_buff[*txbd_curr], addr, addr);
        dma_unmap_len_set(&priv->tx_buff[*txbd_curr], len, len);

        priv->txbd[*txbd_curr].data = cpu_to_le32(addr);

        /* Make sure pointer to data buffer is set */
        wmb();

        skb_tx_timestamp(skb);

        *info = cpu_to_le32(FOR_EMAC | FIRST_OR_LAST_MASK | len);

        /* Make sure info word is set */
        wmb();

        priv->tx_buff[*txbd_curr].skb = skb;

        /* Increment index to point to the next BD */
        *txbd_curr = (*txbd_curr + 1) % TX_BD_NUM;

        /* Ensure that tx_clean() sees the new txbd_curr before
         * checking the queue status. This prevents an unneeded wake
         * of the queue in tx_clean().
         */
        smp_mb();

        if (!arc_emac_tx_avail(priv)) {
                netif_stop_queue(ndev);
                /* Refresh tx_dirty */
                smp_mb();
                if (arc_emac_tx_avail(priv))
                        netif_start_queue(ndev);
        }

        arc_reg_set(priv, R_STATUS, TXPL_MASK);

        return NETDEV_TX_OK;
}

static void arc_emac_set_address_internal(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        unsigned int addr_low, addr_hi;

        addr_low = le32_to_cpu(*(__le32 *)&ndev->dev_addr[0]);
        addr_hi = le16_to_cpu(*(__le16 *)&ndev->dev_addr[4]);

        arc_reg_set(priv, R_ADDRL, addr_low);
        arc_reg_set(priv, R_ADDRH, addr_hi);
}

/**
 * arc_emac_set_address - Set the MAC address for this device.
 * @ndev:       Pointer to net_device structure.
 * @p:          6 byte Address to be written as MAC address.
 *
 * This function copies the HW address from the sockaddr structure to the
 * net_device structure and updates the address in HW.
 *
 * returns:     -EBUSY if the net device is busy or 0 if the address is set
 *              successfully.
 */
static int arc_emac_set_address(struct net_device *ndev, void *p)
{
        struct sockaddr *addr = p;

        if (netif_running(ndev))
                return -EBUSY;

        if (!is_valid_ether_addr(addr->sa_data))
                return -EADDRNOTAVAIL;

        memcpy(ndev->dev_addr, addr->sa_data, ndev->addr_len);

        arc_emac_set_address_internal(ndev);

        return 0;
}

/**
 * arc_emac_restart - Restart EMAC
 * @ndev:       Pointer to net_device structure.
 *
 * This function do hardware reset of EMAC in order to restore
 * network packets reception.
 */
static void arc_emac_restart(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        int i;

        if (net_ratelimit())
                netdev_warn(ndev, "restarting stalled EMAC\n");

        netif_stop_queue(ndev);

        /* Disable interrupts */
        arc_reg_clr(priv, R_ENABLE, RXINT_MASK | TXINT_MASK | ERR_MASK);

        /* Disable EMAC */
        arc_reg_clr(priv, R_CTRL, EN_MASK);

        /* Return the sk_buff to system */
        arc_free_tx_queue(ndev);

        /* Clean Tx BD's */
        priv->txbd_curr = 0;
        priv->txbd_dirty = 0;
        memset(priv->txbd, 0, TX_RING_SZ);

        for (i = 0; i < RX_BD_NUM; i++) {
                struct arc_emac_bd *rxbd = &priv->rxbd[i];
                unsigned int info = le32_to_cpu(rxbd->info);

                if (!(info & FOR_EMAC)) {
                        stats->rx_errors++;
                        stats->rx_dropped++;
                }
                /* Return ownership to EMAC */
                rxbd->info = cpu_to_le32(FOR_EMAC | EMAC_BUFFER_SIZE);
        }
        priv->last_rx_bd = 0;

        /* Make sure info is visible to EMAC before enable */
        wmb();

        /* Enable interrupts */
        arc_reg_set(priv, R_ENABLE, RXINT_MASK | TXINT_MASK | ERR_MASK);

        /* Enable EMAC */
        arc_reg_or(priv, R_CTRL, EN_MASK);

        netif_start_queue(ndev);
}

static const struct net_device_ops arc_emac_netdev_ops = {
        .ndo_open               = arc_emac_open,
        .ndo_stop               = arc_emac_stop,
        .ndo_start_xmit         = arc_emac_tx,
        .ndo_set_mac_address    = arc_emac_set_address,
        .ndo_get_stats          = arc_emac_stats,
        .ndo_set_rx_mode        = arc_emac_set_rx_mode,
        .ndo_do_ioctl           = phy_do_ioctl_running,
#ifdef CONFIG_NET_POLL_CONTROLLER
        .ndo_poll_controller    = arc_emac_poll_controller,
#endif
};

int arc_emac_probe(struct net_device *ndev, int interface)
{
        struct device *dev = ndev->dev.parent;
        struct resource res_regs;
        struct device_node *phy_node;
        struct phy_device *phydev = NULL;
        struct arc_emac_priv *priv;
        const char *mac_addr;
        unsigned int id, clock_frequency, irq;
        int err;

        /* Get PHY from device tree */
        phy_node = of_parse_phandle(dev->of_node, "phy", 0);
        if (!phy_node) {
                dev_err(dev, "failed to retrieve phy description from device tree\n");
                return -ENODEV;
        }

        /* Get EMAC registers base address from device tree */
        err = of_address_to_resource(dev->of_node, 0, &res_regs);
        if (err) {
                dev_err(dev, "failed to retrieve registers base from device tree\n");
                err = -ENODEV;
                goto out_put_node;
        }

        /* Get IRQ from device tree */
        irq = irq_of_parse_and_map(dev->of_node, 0);
        if (!irq) {
                dev_err(dev, "failed to retrieve <irq> value from device tree\n");
                err = -ENODEV;
                goto out_put_node;
        }

        ndev->netdev_ops = &arc_emac_netdev_ops;
        ndev->ethtool_ops = &arc_emac_ethtool_ops;
        ndev->watchdog_timeo = TX_TIMEOUT;

        priv = netdev_priv(ndev);
        priv->dev = dev;

        priv->regs = devm_ioremap_resource(dev, &res_regs);
        if (IS_ERR(priv->regs)) {
                err = PTR_ERR(priv->regs);
                goto out_put_node;
        }

        dev_dbg(dev, "Registers base address is 0x%p\n", priv->regs);

        if (priv->clk) {
                err = clk_prepare_enable(priv->clk);
                if (err) {
                        dev_err(dev, "failed to enable clock\n");
                        goto out_put_node;
                }

                clock_frequency = clk_get_rate(priv->clk);
        } else {
                /* Get CPU clock frequency from device tree */
                if (of_property_read_u32(dev->of_node, "clock-frequency",
                                         &clock_frequency)) {
                        dev_err(dev, "failed to retrieve <clock-frequency> from device tree\n");
                        err = -EINVAL;
                        goto out_put_node;
                }
        }

        id = arc_reg_get(priv, R_ID);

        /* Check for EMAC revision 5 or 7, magic number */
        if (!(id == 0x0005fd02 || id == 0x0007fd02)) {
                dev_err(dev, "ARC EMAC not detected, id=0x%x\n", id);
                err = -ENODEV;
                goto out_clken;
        }
        dev_info(dev, "ARC EMAC detected with id: 0x%x\n", id);

        /* Set poll rate so that it polls every 1 ms */
        arc_reg_set(priv, R_POLLRATE, clock_frequency / 1000000);

        ndev->irq = irq;
        dev_info(dev, "IRQ is %d\n", ndev->irq);

        /* Register interrupt handler for device */
        err = devm_request_irq(dev, ndev->irq, arc_emac_intr, 0,
                               ndev->name, ndev);
        if (err) {
                dev_err(dev, "could not allocate IRQ\n");
                goto out_clken;
        }

        /* Get MAC address from device tree */
        mac_addr = of_get_mac_address(dev->of_node);

        if (!IS_ERR(mac_addr))
                ether_addr_copy(ndev->dev_addr, mac_addr);
        else
                eth_hw_addr_random(ndev);

        arc_emac_set_address_internal(ndev);
        dev_info(dev, "MAC address is now %pM\n", ndev->dev_addr);

        /* Do 1 allocation instead of 2 separate ones for Rx and Tx BD rings */
        priv->rxbd = dmam_alloc_coherent(dev, RX_RING_SZ + TX_RING_SZ,
                                         &priv->rxbd_dma, GFP_KERNEL);

        if (!priv->rxbd) {
                dev_err(dev, "failed to allocate data buffers\n");
                err = -ENOMEM;
                goto out_clken;
        }

        priv->txbd = priv->rxbd + RX_BD_NUM;

        priv->txbd_dma = priv->rxbd_dma + RX_RING_SZ;
        dev_dbg(dev, "EMAC Device addr: Rx Ring [0x%x], Tx Ring[%x]\n",
                (unsigned int)priv->rxbd_dma, (unsigned int)priv->txbd_dma);

        err = arc_mdio_probe(priv);
        if (err) {
                dev_err(dev, "failed to probe MII bus\n");
                goto out_clken;
        }

        phydev = of_phy_connect(ndev, phy_node, arc_emac_adjust_link, 0,
                                interface);
        if (!phydev) {
                dev_err(dev, "of_phy_connect() failed\n");
                err = -ENODEV;
                goto out_mdio;
        }

        dev_info(dev, "connected to %s phy with id 0x%x\n",
                 phydev->drv->name, phydev->phy_id);

        netif_napi_add(ndev, &priv->napi, arc_emac_poll, ARC_EMAC_NAPI_WEIGHT);

        err = register_netdev(ndev);
        if (err) {
                dev_err(dev, "failed to register network device\n");
                goto out_netif_api;
        }

        of_node_put(phy_node);
        return 0;

out_netif_api:
        netif_napi_del(&priv->napi);
        phy_disconnect(phydev);
out_mdio:
        arc_mdio_remove(priv);
out_clken:
        if (priv->clk)
                clk_disable_unprepare(priv->clk);
out_put_node:
        of_node_put(phy_node);

        return err;
}
EXPORT_SYMBOL_GPL(arc_emac_probe);

int arc_emac_remove(struct net_device *ndev)
{
        struct arc_emac_priv *priv = netdev_priv(ndev);

        phy_disconnect(ndev->phydev);
        arc_mdio_remove(priv);
        unregister_netdev(ndev);
        netif_napi_del(&priv->napi);

        if (!IS_ERR(priv->clk))
                clk_disable_unprepare(priv->clk);

        return 0;
}
EXPORT_SYMBOL_GPL(arc_emac_remove);

MODULE_AUTHOR("Alexey Brodkin <abrodkin@synopsys.com>");
MODULE_DESCRIPTION("ARC EMAC driver");
MODULE_LICENSE("GPL");