/*
 * Xilinx EmacLite Linux driver for the Xilinx Ethernet MAC Lite device.
 *
 * This is a new flat driver which is based on the original emac_lite
 * driver from John Williams <john.williams@xilinx.com>.
 *
 * 2007 - 2013 (c) Xilinx, Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 */

#include <linux/module.h>
#include <linux/uaccess.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/of_mdio.h>
#include <linux/of_net.h>
#include <linux/phy.h>
#include <linux/interrupt.h>

#define DRIVER_NAME "xilinx_emaclite"

/* Register offsets for the EmacLite Core */
#define XEL_TXBUFF_OFFSET       0x0             /* Transmit Buffer */
#define XEL_MDIOADDR_OFFSET     0x07E4          /* MDIO Address Register */
#define XEL_MDIOWR_OFFSET       0x07E8          /* MDIO Write Data Register */
#define XEL_MDIORD_OFFSET       0x07EC          /* MDIO Read Data Register */
#define XEL_MDIOCTRL_OFFSET     0x07F0          /* MDIO Control Register */
#define XEL_GIER_OFFSET         0x07F8          /* GIE Register */
#define XEL_TSR_OFFSET          0x07FC          /* Tx status */
#define XEL_TPLR_OFFSET         0x07F4          /* Tx packet length */

#define XEL_RXBUFF_OFFSET       0x1000          /* Receive Buffer */
#define XEL_RPLR_OFFSET         0x100C          /* Rx packet length */
#define XEL_RSR_OFFSET          0x17FC          /* Rx status */

#define XEL_BUFFER_OFFSET       0x0800          /* Next Tx/Rx buffer's offset */

/* MDIO Address Register Bit Masks */
#define XEL_MDIOADDR_REGADR_MASK  0x0000001F    /* Register Address */
#define XEL_MDIOADDR_PHYADR_MASK  0x000003E0    /* PHY Address */
#define XEL_MDIOADDR_PHYADR_SHIFT 5
#define XEL_MDIOADDR_OP_MASK      0x00000400    /* RD/WR Operation */

/* MDIO Write Data Register Bit Masks */
#define XEL_MDIOWR_WRDATA_MASK    0x0000FFFF    /* Data to be Written */

/* MDIO Read Data Register Bit Masks */
#define XEL_MDIORD_RDDATA_MASK    0x0000FFFF    /* Data to be Read */

/* MDIO Control Register Bit Masks */
#define XEL_MDIOCTRL_MDIOSTS_MASK 0x00000001    /* MDIO Status Mask */
#define XEL_MDIOCTRL_MDIOEN_MASK  0x00000008    /* MDIO Enable */

/* Global Interrupt Enable Register (GIER) Bit Masks */
#define XEL_GIER_GIE_MASK       0x80000000      /* Global Enable */

/* Transmit Status Register (TSR) Bit Masks */
#define XEL_TSR_XMIT_BUSY_MASK   0x00000001     /* Tx complete */
#define XEL_TSR_PROGRAM_MASK     0x00000002     /* Program the MAC address */
#define XEL_TSR_XMIT_IE_MASK     0x00000008     /* Tx interrupt enable bit */
#define XEL_TSR_XMIT_ACTIVE_MASK 0x80000000     /* Buffer is active, SW bit
                                                 * only. This is not documented
                                                 * in the HW spec */

/* Define for programming the MAC address into the EmacLite */
#define XEL_TSR_PROG_MAC_ADDR   (XEL_TSR_XMIT_BUSY_MASK | XEL_TSR_PROGRAM_MASK)

/* Receive Status Register (RSR) */
#define XEL_RSR_RECV_DONE_MASK  0x00000001      /* Rx complete */
#define XEL_RSR_RECV_IE_MASK    0x00000008      /* Rx interrupt enable bit */

/* Transmit Packet Length Register (TPLR) */
#define XEL_TPLR_LENGTH_MASK    0x0000FFFF      /* Tx packet length */

/* Receive Packet Length Register (RPLR) */
#define XEL_RPLR_LENGTH_MASK    0x0000FFFF      /* Rx packet length */

#define XEL_HEADER_OFFSET       12              /* Offset to length field */
#define XEL_HEADER_SHIFT        16              /* Shift value for length */

/* General Ethernet Definitions */
#define XEL_ARP_PACKET_SIZE             28      /* Max ARP packet size */
#define XEL_HEADER_IP_LENGTH_OFFSET     16      /* IP Length Offset */



#define TX_TIMEOUT              (60*HZ)         /* Tx timeout is 60 seconds. */
#define ALIGNMENT               4

/* BUFFER_ALIGN(adr) calculates the number of bytes to the next alignment. */
#define BUFFER_ALIGN(adr) ((ALIGNMENT - ((u32) adr)) % ALIGNMENT)

#ifdef __BIG_ENDIAN
#define xemaclite_readl         ioread32be
#define xemaclite_writel        iowrite32be
#else
#define xemaclite_readl         ioread32
#define xemaclite_writel        iowrite32
#endif

/**
 * struct net_local - Our private per device data
 * @ndev:               instance of the network device
 * @tx_ping_pong:       indicates whether Tx Pong buffer is configured in HW
 * @rx_ping_pong:       indicates whether Rx Pong buffer is configured in HW
 * @next_tx_buf_to_use: next Tx buffer to write to
 * @next_rx_buf_to_use: next Rx buffer to read from
 * @base_addr:          base address of the Emaclite device
 * @reset_lock:         lock used for synchronization
 * @deferred_skb:       holds an skb (for transmission at a later time) when the
 *                      Tx buffer is not free
 * @phy_dev:            pointer to the PHY device
 * @phy_node:           pointer to the PHY device node
 * @mii_bus:            pointer to the MII bus
 * @last_link:          last link status
 */
struct net_local {

        struct net_device *ndev;

        bool tx_ping_pong;
        bool rx_ping_pong;
        u32 next_tx_buf_to_use;
        u32 next_rx_buf_to_use;
        void __iomem *base_addr;

        spinlock_t reset_lock;
        struct sk_buff *deferred_skb;

        struct phy_device *phy_dev;
        struct device_node *phy_node;

        struct mii_bus *mii_bus;

        int last_link;
};


/*************************/
/* EmacLite driver calls */
/*************************/

/**
 * xemaclite_enable_interrupts - Enable the interrupts for the EmacLite device
 * @drvdata:    Pointer to the Emaclite device private data
 *
 * This function enables the Tx and Rx interrupts for the Emaclite device along
 * with the Global Interrupt Enable.
 */
static void xemaclite_enable_interrupts(struct net_local *drvdata)
{
        u32 reg_data;

        /* Enable the Tx interrupts for the first Buffer */
        reg_data = xemaclite_readl(drvdata->base_addr + XEL_TSR_OFFSET);
        xemaclite_writel(reg_data | XEL_TSR_XMIT_IE_MASK,
                         drvdata->base_addr + XEL_TSR_OFFSET);

        /* Enable the Rx interrupts for the first buffer */
        xemaclite_writel(XEL_RSR_RECV_IE_MASK, drvdata->base_addr + XEL_RSR_OFFSET);

        /* Enable the Global Interrupt Enable */
        xemaclite_writel(XEL_GIER_GIE_MASK, drvdata->base_addr + XEL_GIER_OFFSET);
}

/**
 * xemaclite_disable_interrupts - Disable the interrupts for the EmacLite device
 * @drvdata:    Pointer to the Emaclite device private data
 *
 * This function disables the Tx and Rx interrupts for the Emaclite device,
 * along with the Global Interrupt Enable.
 */
static void xemaclite_disable_interrupts(struct net_local *drvdata)
{
        u32 reg_data;

        /* Disable the Global Interrupt Enable */
        xemaclite_writel(XEL_GIER_GIE_MASK, drvdata->base_addr + XEL_GIER_OFFSET);

        /* Disable the Tx interrupts for the first buffer */
        reg_data = xemaclite_readl(drvdata->base_addr + XEL_TSR_OFFSET);
        xemaclite_writel(reg_data & (~XEL_TSR_XMIT_IE_MASK),
                         drvdata->base_addr + XEL_TSR_OFFSET);

        /* Disable the Rx interrupts for the first buffer */
        reg_data = xemaclite_readl(drvdata->base_addr + XEL_RSR_OFFSET);
        xemaclite_writel(reg_data & (~XEL_RSR_RECV_IE_MASK),
                         drvdata->base_addr + XEL_RSR_OFFSET);
}

/**
 * xemaclite_aligned_write - Write from 16-bit aligned to 32-bit aligned address
 * @src_ptr:    Void pointer to the 16-bit aligned source address
 * @dest_ptr:   Pointer to the 32-bit aligned destination address
 * @length:     Number bytes to write from source to destination
 *
 * This function writes data from a 16-bit aligned buffer to a 32-bit aligned
 * address in the EmacLite device.
 */
static void xemaclite_aligned_write(void *src_ptr, u32 *dest_ptr,
                                    unsigned length)
{
        u32 align_buffer;
        u32 *to_u32_ptr;
        u16 *from_u16_ptr, *to_u16_ptr;

        to_u32_ptr = dest_ptr;
        from_u16_ptr = src_ptr;
        align_buffer = 0;

        for (; length > 3; length -= 4) {
                to_u16_ptr = (u16 *)&align_buffer;
                *to_u16_ptr++ = *from_u16_ptr++;
                *to_u16_ptr++ = *from_u16_ptr++;

                /* This barrier resolves occasional issues seen around
                 * cases where the data is not properly flushed out
                 * from the processor store buffers to the destination
                 * memory locations.
                 */
                wmb();

                /* Output a word */
                *to_u32_ptr++ = align_buffer;
        }
        if (length) {
                u8 *from_u8_ptr, *to_u8_ptr;

                /* Set up to output the remaining data */
                align_buffer = 0;
                to_u8_ptr = (u8 *) &align_buffer;
                from_u8_ptr = (u8 *) from_u16_ptr;

                /* Output the remaining data */
                for (; length > 0; length--)
                        *to_u8_ptr++ = *from_u8_ptr++;

                /* This barrier resolves occasional issues seen around
                 * cases where the data is not properly flushed out
                 * from the processor store buffers to the destination
                 * memory locations.
                 */
                wmb();
                *to_u32_ptr = align_buffer;
        }
}

/**
 * xemaclite_aligned_read - Read from 32-bit aligned to 16-bit aligned buffer
 * @src_ptr:    Pointer to the 32-bit aligned source address
 * @dest_ptr:   Pointer to the 16-bit aligned destination address
 * @length:     Number bytes to read from source to destination
 *
 * This function reads data from a 32-bit aligned address in the EmacLite device
 * to a 16-bit aligned buffer.
 */
static void xemaclite_aligned_read(u32 *src_ptr, u8 *dest_ptr,
                                   unsigned length)
{
        u16 *to_u16_ptr, *from_u16_ptr;
        u32 *from_u32_ptr;
        u32 align_buffer;

        from_u32_ptr = src_ptr;
        to_u16_ptr = (u16 *) dest_ptr;

        for (; length > 3; length -= 4) {
                /* Copy each word into the temporary buffer */
                align_buffer = *from_u32_ptr++;
                from_u16_ptr = (u16 *)&align_buffer;

                /* Read data from source */
                *to_u16_ptr++ = *from_u16_ptr++;
                *to_u16_ptr++ = *from_u16_ptr++;
        }

        if (length) {
                u8 *to_u8_ptr, *from_u8_ptr;

                /* Set up to read the remaining data */
                to_u8_ptr = (u8 *) to_u16_ptr;
                align_buffer = *from_u32_ptr++;
                from_u8_ptr = (u8 *) &align_buffer;

                /* Read the remaining data */
                for (; length > 0; length--)
                        *to_u8_ptr = *from_u8_ptr;
        }
}

/**
 * xemaclite_send_data - Send an Ethernet frame
 * @drvdata:    Pointer to the Emaclite device private data
 * @data:       Pointer to the data to be sent
 * @byte_count: Total frame size, including header
 *
 * This function checks if the Tx buffer of the Emaclite device is free to send
 * data. If so, it fills the Tx buffer with data for transmission. Otherwise, it
 * returns an error.
 *
 * Return:      0 upon success or -1 if the buffer(s) are full.
 *
 * Note:        The maximum Tx packet size can not be more than Ethernet header
 *              (14 Bytes) + Maximum MTU (1500 bytes). This is excluding FCS.
 */
static int xemaclite_send_data(struct net_local *drvdata, u8 *data,
                               unsigned int byte_count)
{
        u32 reg_data;
        void __iomem *addr;

        /* Determine the expected Tx buffer address */
        addr = drvdata->base_addr + drvdata->next_tx_buf_to_use;

        /* If the length is too large, truncate it */
        if (byte_count > ETH_FRAME_LEN)
                byte_count = ETH_FRAME_LEN;

        /* Check if the expected buffer is available */
        reg_data = xemaclite_readl(addr + XEL_TSR_OFFSET);
        if ((reg_data & (XEL_TSR_XMIT_BUSY_MASK |
             XEL_TSR_XMIT_ACTIVE_MASK)) == 0) {

                /* Switch to next buffer if configured */
                if (drvdata->tx_ping_pong != 0)
                        drvdata->next_tx_buf_to_use ^= XEL_BUFFER_OFFSET;
        } else if (drvdata->tx_ping_pong != 0) {
                /* If the expected buffer is full, try the other buffer,
                 * if it is configured in HW */

                addr = (void __iomem __force *)((u32 __force)addr ^
                                                 XEL_BUFFER_OFFSET);
                reg_data = xemaclite_readl(addr + XEL_TSR_OFFSET);

                if ((reg_data & (XEL_TSR_XMIT_BUSY_MASK |
                     XEL_TSR_XMIT_ACTIVE_MASK)) != 0)
                        return -1; /* Buffers were full, return failure */
        } else
                return -1; /* Buffer was full, return failure */

        /* Write the frame to the buffer */
        xemaclite_aligned_write(data, (u32 __force *) addr, byte_count);

        xemaclite_writel((byte_count & XEL_TPLR_LENGTH_MASK),
                         addr + XEL_TPLR_OFFSET);

        /* Update the Tx Status Register to indicate that there is a
         * frame to send. Set the XEL_TSR_XMIT_ACTIVE_MASK flag which
         * is used by the interrupt handler to check whether a frame
         * has been transmitted */
        reg_data = xemaclite_readl(addr + XEL_TSR_OFFSET);
        reg_data |= (XEL_TSR_XMIT_BUSY_MASK | XEL_TSR_XMIT_ACTIVE_MASK);
        xemaclite_writel(reg_data, addr + XEL_TSR_OFFSET);

        return 0;
}

/**
 * xemaclite_recv_data - Receive a frame
 * @drvdata:    Pointer to the Emaclite device private data
 * @data:       Address where the data is to be received
 *
 * This function is intended to be called from the interrupt context or
 * with a wrapper which waits for the receive frame to be available.
 *
 * Return:      Total number of bytes received
 */
static u16 xemaclite_recv_data(struct net_local *drvdata, u8 *data, int maxlen)
{
        void __iomem *addr;
        u16 length, proto_type;
        u32 reg_data;

        /* Determine the expected buffer address */
        addr = (drvdata->base_addr + drvdata->next_rx_buf_to_use);

        /* Verify which buffer has valid data */
        reg_data = xemaclite_readl(addr + XEL_RSR_OFFSET);

        if ((reg_data & XEL_RSR_RECV_DONE_MASK) == XEL_RSR_RECV_DONE_MASK) {
                if (drvdata->rx_ping_pong != 0)
                        drvdata->next_rx_buf_to_use ^= XEL_BUFFER_OFFSET;
        } else {
                /* The instance is out of sync, try other buffer if other
                 * buffer is configured, return 0 otherwise. If the instance is
                 * out of sync, do not update the 'next_rx_buf_to_use' since it
                 * will correct on subsequent calls */
                if (drvdata->rx_ping_pong != 0)
                        addr = (void __iomem __force *)((u32 __force)addr ^
                                                         XEL_BUFFER_OFFSET);
                else
                        return 0;       /* No data was available */

                /* Verify that buffer has valid data */
                reg_data = xemaclite_readl(addr + XEL_RSR_OFFSET);
                if ((reg_data & XEL_RSR_RECV_DONE_MASK) !=
                     XEL_RSR_RECV_DONE_MASK)
                        return 0;       /* No data was available */
        }

        /* Get the protocol type of the ethernet frame that arrived */
        proto_type = ((ntohl(xemaclite_readl(addr + XEL_HEADER_OFFSET +
                        XEL_RXBUFF_OFFSET)) >> XEL_HEADER_SHIFT) &
                        XEL_RPLR_LENGTH_MASK);

        /* Check if received ethernet frame is a raw ethernet frame
         * or an IP packet or an ARP packet */
        if (proto_type > ETH_DATA_LEN) {

                if (proto_type == ETH_P_IP) {
                        length = ((ntohl(xemaclite_readl(addr +
                                        XEL_HEADER_IP_LENGTH_OFFSET +
                                        XEL_RXBUFF_OFFSET)) >>
                                        XEL_HEADER_SHIFT) &
                                        XEL_RPLR_LENGTH_MASK);
                        length = min_t(u16, length, ETH_DATA_LEN);
                        length += ETH_HLEN + ETH_FCS_LEN;

                } else if (proto_type == ETH_P_ARP)
                        length = XEL_ARP_PACKET_SIZE + ETH_HLEN + ETH_FCS_LEN;
                else
                        /* Field contains type other than IP or ARP, use max
                         * frame size and let user parse it */
                        length = ETH_FRAME_LEN + ETH_FCS_LEN;
        } else
                /* Use the length in the frame, plus the header and trailer */
                length = proto_type + ETH_HLEN + ETH_FCS_LEN;

        if (WARN_ON(length > maxlen))
                length = maxlen;

        /* Read from the EmacLite device */
        xemaclite_aligned_read((u32 __force *) (addr + XEL_RXBUFF_OFFSET),
                                data, length);

        /* Acknowledge the frame */
        reg_data = xemaclite_readl(addr + XEL_RSR_OFFSET);
        reg_data &= ~XEL_RSR_RECV_DONE_MASK;
        xemaclite_writel(reg_data, addr + XEL_RSR_OFFSET);

        return length;
}

/**
 * xemaclite_update_address - Update the MAC address in the device
 * @drvdata:    Pointer to the Emaclite device private data
 * @address_ptr:Pointer to the MAC address (MAC address is a 48-bit value)
 *
 * Tx must be idle and Rx should be idle for deterministic results.
 * It is recommended that this function should be called after the
 * initialization and before transmission of any packets from the device.
 * The MAC address can be programmed using any of the two transmit
 * buffers (if configured).
 */
static void xemaclite_update_address(struct net_local *drvdata,
                                     u8 *address_ptr)
{
        void __iomem *addr;
        u32 reg_data;

        /* Determine the expected Tx buffer address */
        addr = drvdata->base_addr + drvdata->next_tx_buf_to_use;

        xemaclite_aligned_write(address_ptr, (u32 __force *) addr, ETH_ALEN);

        xemaclite_writel(ETH_ALEN, addr + XEL_TPLR_OFFSET);

        /* Update the MAC address in the EmacLite */
        reg_data = xemaclite_readl(addr + XEL_TSR_OFFSET);
        xemaclite_writel(reg_data | XEL_TSR_PROG_MAC_ADDR, addr + XEL_TSR_OFFSET);

        /* Wait for EmacLite to finish with the MAC address update */
        while ((xemaclite_readl(addr + XEL_TSR_OFFSET) &
                XEL_TSR_PROG_MAC_ADDR) != 0)
                ;
}

/**
 * xemaclite_set_mac_address - Set the MAC address for this device
 * @dev:        Pointer to the network device instance
 * @addr:       Void pointer to the sockaddr structure
 *
 * This function copies the HW address from the sockaddr strucutre to the
 * net_device structure and updates the address in HW.
 *
 * Return:      Error if the net device is busy or 0 if the addr is set
 *              successfully
 */
static int xemaclite_set_mac_address(struct net_device *dev, void *address)
{
        struct net_local *lp = netdev_priv(dev);
        struct sockaddr *addr = address;

        if (netif_running(dev))
                return -EBUSY;

        memcpy(dev->dev_addr, addr->sa_data, dev->addr_len);
        xemaclite_update_address(lp, dev->dev_addr);
        return 0;
}

/**
 * xemaclite_tx_timeout - Callback for Tx Timeout
 * @dev:        Pointer to the network device
 *
 * This function is called when Tx time out occurs for Emaclite device.
 */
static void xemaclite_tx_timeout(struct net_device *dev, unsigned int txqueue)
{
        struct net_local *lp = netdev_priv(dev);
        unsigned long flags;

        dev_err(&lp->ndev->dev, "Exceeded transmit timeout of %lu ms\n",
                TX_TIMEOUT * 1000UL / HZ);

        dev->stats.tx_errors++;

        /* Reset the device */
        spin_lock_irqsave(&lp->reset_lock, flags);

        /* Shouldn't really be necessary, but shouldn't hurt */
        netif_stop_queue(dev);

        xemaclite_disable_interrupts(lp);
        xemaclite_enable_interrupts(lp);

        if (lp->deferred_skb) {
                dev_kfree_skb(lp->deferred_skb);
                lp->deferred_skb = NULL;
                dev->stats.tx_errors++;
        }

        /* To exclude tx timeout */
        netif_trans_update(dev); /* prevent tx timeout */

        /* We're all ready to go. Start the queue */
        netif_wake_queue(dev);
        spin_unlock_irqrestore(&lp->reset_lock, flags);
}

/**********************/
/* Interrupt Handlers */
/**********************/

/**
 * xemaclite_tx_handler - Interrupt handler for frames sent
 * @dev:        Pointer to the network device
 *
 * This function updates the number of packets transmitted and handles the
 * deferred skb, if there is one.
 */
static void xemaclite_tx_handler(struct net_device *dev)
{
        struct net_local *lp = netdev_priv(dev);

        dev->stats.tx_packets++;
        if (lp->deferred_skb) {
                if (xemaclite_send_data(lp,
                                        (u8 *) lp->deferred_skb->data,
                                        lp->deferred_skb->len) != 0)
                        return;
                else {
                        dev->stats.tx_bytes += lp->deferred_skb->len;
                        dev_kfree_skb_irq(lp->deferred_skb);
                        lp->deferred_skb = NULL;
                        netif_trans_update(dev); /* prevent tx timeout */
                        netif_wake_queue(dev);
                }
        }
}

/**
 * xemaclite_rx_handler- Interrupt handler for frames received
 * @dev:        Pointer to the network device
 *
 * This function allocates memory for a socket buffer, fills it with data
 * received and hands it over to the TCP/IP stack.
 */
static void xemaclite_rx_handler(struct net_device *dev)
{
        struct net_local *lp = netdev_priv(dev);
        struct sk_buff *skb;
        unsigned int align;
        u32 len;

        len = ETH_FRAME_LEN + ETH_FCS_LEN;
        skb = netdev_alloc_skb(dev, len + ALIGNMENT);
        if (!skb) {
                /* Couldn't get memory. */
                dev->stats.rx_dropped++;
                dev_err(&lp->ndev->dev, "Could not allocate receive buffer\n");
                return;
        }

        /*
         * A new skb should have the data halfword aligned, but this code is
         * here just in case that isn't true. Calculate how many
         * bytes we should reserve to get the data to start on a word
         * boundary */
        align = BUFFER_ALIGN(skb->data);
        if (align)
                skb_reserve(skb, align);

        skb_reserve(skb, 2);

        len = xemaclite_recv_data(lp, (u8 *) skb->data, len);

        if (!len) {
                dev->stats.rx_errors++;
                dev_kfree_skb_irq(skb);
                return;
        }

        skb_put(skb, len);      /* Tell the skb how much data we got */

        skb->protocol = eth_type_trans(skb, dev);
        skb_checksum_none_assert(skb);

        dev->stats.rx_packets++;
        dev->stats.rx_bytes += len;

        if (!skb_defer_rx_timestamp(skb))
                netif_rx(skb);  /* Send the packet upstream */
}

/**
 * xemaclite_interrupt - Interrupt handler for this driver
 * @irq:        Irq of the Emaclite device
 * @dev_id:     Void pointer to the network device instance used as callback
 *              reference
 *
 * This function handles the Tx and Rx interrupts of the EmacLite device.
 */
static irqreturn_t xemaclite_interrupt(int irq, void *dev_id)
{
        bool tx_complete = false;
        struct net_device *dev = dev_id;
        struct net_local *lp = netdev_priv(dev);
        void __iomem *base_addr = lp->base_addr;
        u32 tx_status;

        /* Check if there is Rx Data available */
        if ((xemaclite_readl(base_addr + XEL_RSR_OFFSET) &
                         XEL_RSR_RECV_DONE_MASK) ||
            (xemaclite_readl(base_addr + XEL_BUFFER_OFFSET + XEL_RSR_OFFSET)
                         & XEL_RSR_RECV_DONE_MASK))

                xemaclite_rx_handler(dev);

        /* Check if the Transmission for the first buffer is completed */
        tx_status = xemaclite_readl(base_addr + XEL_TSR_OFFSET);
        if (((tx_status & XEL_TSR_XMIT_BUSY_MASK) == 0) &&
                (tx_status & XEL_TSR_XMIT_ACTIVE_MASK) != 0) {

                tx_status &= ~XEL_TSR_XMIT_ACTIVE_MASK;
                xemaclite_writel(tx_status, base_addr + XEL_TSR_OFFSET);

                tx_complete = true;
        }

        /* Check if the Transmission for the second buffer is completed */
        tx_status = xemaclite_readl(base_addr + XEL_BUFFER_OFFSET + XEL_TSR_OFFSET);
        if (((tx_status & XEL_TSR_XMIT_BUSY_MASK) == 0) &&
                (tx_status & XEL_TSR_XMIT_ACTIVE_MASK) != 0) {

                tx_status &= ~XEL_TSR_XMIT_ACTIVE_MASK;
                xemaclite_writel(tx_status, base_addr + XEL_BUFFER_OFFSET +
                                 XEL_TSR_OFFSET);

                tx_complete = true;
        }

        /* If there was a Tx interrupt, call the Tx Handler */
        if (tx_complete != 0)
                xemaclite_tx_handler(dev);

        return IRQ_HANDLED;
}

/**********************/
/* MDIO Bus functions */
/**********************/

/**
 * xemaclite_mdio_wait - Wait for the MDIO to be ready to use
 * @lp:         Pointer to the Emaclite device private data
 *
 * This function waits till the device is ready to accept a new MDIO
 * request.
 *
 * Return:      0 for success or ETIMEDOUT for a timeout
 */

static int xemaclite_mdio_wait(struct net_local *lp)
{
        unsigned long end = jiffies + 2;

        /* wait for the MDIO interface to not be busy or timeout
           after some time.
        */
        while (xemaclite_readl(lp->base_addr + XEL_MDIOCTRL_OFFSET) &
                        XEL_MDIOCTRL_MDIOSTS_MASK) {
                if (time_before_eq(end, jiffies)) {
                        WARN_ON(1);
                        return -ETIMEDOUT;
                }
                msleep(1);
        }
        return 0;
}

/**
 * xemaclite_mdio_read - Read from a given MII management register
 * @bus:        the mii_bus struct
 * @phy_id:     the phy address
 * @reg:        register number to read from
 *
 * This function waits till the device is ready to accept a new MDIO
 * request and then writes the phy address to the MDIO Address register
 * and reads data from MDIO Read Data register, when its available.
 *
 * Return:      Value read from the MII management register
 */
static int xemaclite_mdio_read(struct mii_bus *bus, int phy_id, int reg)
{
        struct net_local *lp = bus->priv;
        u32 ctrl_reg;
        u32 rc;

        if (xemaclite_mdio_wait(lp))
                return -ETIMEDOUT;

        /* Write the PHY address, register number and set the OP bit in the
         * MDIO Address register. Set the Status bit in the MDIO Control
         * register to start a MDIO read transaction.
         */
        ctrl_reg = xemaclite_readl(lp->base_addr + XEL_MDIOCTRL_OFFSET);
        xemaclite_writel(XEL_MDIOADDR_OP_MASK |
                         ((phy_id << XEL_MDIOADDR_PHYADR_SHIFT) | reg),
                         lp->base_addr + XEL_MDIOADDR_OFFSET);
        xemaclite_writel(ctrl_reg | XEL_MDIOCTRL_MDIOSTS_MASK,
                         lp->base_addr + XEL_MDIOCTRL_OFFSET);

        if (xemaclite_mdio_wait(lp))
                return -ETIMEDOUT;

        rc = xemaclite_readl(lp->base_addr + XEL_MDIORD_OFFSET);

        dev_dbg(&lp->ndev->dev,
                "xemaclite_mdio_read(phy_id=%i, reg=%x) == %x\n",
                phy_id, reg, rc);

        return rc;
}

/**
 * xemaclite_mdio_write - Write to a given MII management register
 * @bus:        the mii_bus struct
 * @phy_id:     the phy address
 * @reg:        register number to write to
 * @val:        value to write to the register number specified by reg
 *
 * This function waits till the device is ready to accept a new MDIO
 * request and then writes the val to the MDIO Write Data register.
 */
static int xemaclite_mdio_write(struct mii_bus *bus, int phy_id, int reg,
                                u16 val)
{
        struct net_local *lp = bus->priv;
        u32 ctrl_reg;

        dev_dbg(&lp->ndev->dev,
                "xemaclite_mdio_write(phy_id=%i, reg=%x, val=%x)\n",
                phy_id, reg, val);

        if (xemaclite_mdio_wait(lp))
                return -ETIMEDOUT;

        /* Write the PHY address, register number and clear the OP bit in the
         * MDIO Address register and then write the value into the MDIO Write
         * Data register. Finally, set the Status bit in the MDIO Control
         * register to start a MDIO write transaction.
         */
        ctrl_reg = xemaclite_readl(lp->base_addr + XEL_MDIOCTRL_OFFSET);
        xemaclite_writel(~XEL_MDIOADDR_OP_MASK &
                         ((phy_id << XEL_MDIOADDR_PHYADR_SHIFT) | reg),
                         lp->base_addr + XEL_MDIOADDR_OFFSET);
        xemaclite_writel(val, lp->base_addr + XEL_MDIOWR_OFFSET);
        xemaclite_writel(ctrl_reg | XEL_MDIOCTRL_MDIOSTS_MASK,
                         lp->base_addr + XEL_MDIOCTRL_OFFSET);

        return 0;
}

/**
 * xemaclite_mdio_setup - Register mii_bus for the Emaclite device
 * @lp:         Pointer to the Emaclite device private data
 * @ofdev:      Pointer to OF device structure
 *
 * This function enables MDIO bus in the Emaclite device and registers a
 * mii_bus.
 *
 * Return:      0 upon success or a negative error upon failure
 */
static int xemaclite_mdio_setup(struct net_local *lp, struct device *dev)
{
        struct mii_bus *bus;
        int rc;
        struct resource res;
        struct device_node *np = of_get_parent(lp->phy_node);
        struct device_node *npp;

        /* Don't register the MDIO bus if the phy_node or its parent node
         * can't be found.
         */
        if (!np) {
                dev_err(dev, "Failed to register mdio bus.\n");
                return -ENODEV;
        }
        npp = of_get_parent(np);

        of_address_to_resource(npp, 0, &res);
        if (lp->ndev->mem_start != res.start) {
                struct phy_device *phydev;
                phydev = of_phy_find_device(lp->phy_node);
                if (!phydev)
                        dev_info(dev,
                                 "MDIO of the phy is not registered yet\n");
                else
                        put_device(&phydev->mdio.dev);
                return 0;
        }

        /* Enable the MDIO bus by asserting the enable bit in MDIO Control
         * register.
         */
        xemaclite_writel(XEL_MDIOCTRL_MDIOEN_MASK,
                         lp->base_addr + XEL_MDIOCTRL_OFFSET);

        bus = mdiobus_alloc();
        if (!bus) {
                dev_err(dev, "Failed to allocate mdiobus\n");
                return -ENOMEM;
        }

        snprintf(bus->id, MII_BUS_ID_SIZE, "%.8llx",
                 (unsigned long long)res.start);
        bus->priv = lp;
        bus->name = "Xilinx Emaclite MDIO";
        bus->read = xemaclite_mdio_read;
        bus->write = xemaclite_mdio_write;
        bus->parent = dev;

        rc = of_mdiobus_register(bus, np);
        if (rc) {
                dev_err(dev, "Failed to register mdio bus.\n");
                goto err_register;
        }

        lp->mii_bus = bus;

        return 0;

err_register:
        mdiobus_free(bus);
        return rc;
}

/**
 * xemaclite_adjust_link - Link state callback for the Emaclite device
 * @ndev: pointer to net_device struct
 *
 * There's nothing in the Emaclite device to be configured when the link
 * state changes. We just print the status.
 */
static void xemaclite_adjust_link(struct net_device *ndev)
{
        struct net_local *lp = netdev_priv(ndev);
        struct phy_device *phy = lp->phy_dev;
        int link_state;

        /* hash together the state values to decide if something has changed */
        link_state = phy->speed | (phy->duplex << 1) | phy->link;

        if (lp->last_link != link_state) {
                lp->last_link = link_state;
                phy_print_status(phy);
        }
}

/**
 * xemaclite_open - Open the network device
 * @dev:        Pointer to the network device
 *
 * This function sets the MAC address, requests an IRQ and enables interrupts
 * for the Emaclite device and starts the Tx queue.
 * It also connects to the phy device, if MDIO is included in Emaclite device.
 */
static int xemaclite_open(struct net_device *dev)
{
        struct net_local *lp = netdev_priv(dev);
        int retval;

        /* Just to be safe, stop the device first */
        xemaclite_disable_interrupts(lp);

        if (lp->phy_node) {
                u32 bmcr;

                lp->phy_dev = of_phy_connect(lp->ndev, lp->phy_node,
                                             xemaclite_adjust_link, 0,
                                             PHY_INTERFACE_MODE_MII);
                if (!lp->phy_dev) {
                        dev_err(&lp->ndev->dev, "of_phy_connect() failed\n");
                        return -ENODEV;
                }

                /* EmacLite doesn't support giga-bit speeds */
                phy_set_max_speed(lp->phy_dev, SPEED_100);

                /* Don't advertise 1000BASE-T Full/Half duplex speeds */
                phy_write(lp->phy_dev, MII_CTRL1000, 0);

                /* Advertise only 10 and 100mbps full/half duplex speeds */
                phy_write(lp->phy_dev, MII_ADVERTISE, ADVERTISE_ALL |
                          ADVERTISE_CSMA);

                /* Restart auto negotiation */
                bmcr = phy_read(lp->phy_dev, MII_BMCR);
                bmcr |= (BMCR_ANENABLE | BMCR_ANRESTART);
                phy_write(lp->phy_dev, MII_BMCR, bmcr);

                phy_start(lp->phy_dev);
        }

        /* Set the MAC address each time opened */
        xemaclite_update_address(lp, dev->dev_addr);

        /* Grab the IRQ */
        retval = request_irq(dev->irq, xemaclite_interrupt, 0, dev->name, dev);
        if (retval) {
                dev_err(&lp->ndev->dev, "Could not allocate interrupt %d\n",
                        dev->irq);
                if (lp->phy_dev)
                        phy_disconnect(lp->phy_dev);
                lp->phy_dev = NULL;

                return retval;
        }

        /* Enable Interrupts */
        xemaclite_enable_interrupts(lp);

        /* We're ready to go */
        netif_start_queue(dev);

        return 0;
}

/**
 * xemaclite_close - Close the network device
 * @dev:        Pointer to the network device
 *
 * This function stops the Tx queue, disables interrupts and frees the IRQ for
 * the Emaclite device.
 * It also disconnects the phy device associated with the Emaclite device.
 */
static int xemaclite_close(struct net_device *dev)
{
        struct net_local *lp = netdev_priv(dev);

        netif_stop_queue(dev);
        xemaclite_disable_interrupts(lp);
        free_irq(dev->irq, dev);

        if (lp->phy_dev)
                phy_disconnect(lp->phy_dev);
        lp->phy_dev = NULL;

        return 0;
}

/**
 * xemaclite_send - Transmit a frame
 * @orig_skb:   Pointer to the socket buffer to be transmitted
 * @dev:        Pointer to the network device
 *
 * This function checks if the Tx buffer of the Emaclite device is free to send
 * data. If so, it fills the Tx buffer with data from socket buffer data,
 * updates the stats and frees the socket buffer. The Tx completion is signaled

 * by an interrupt. If the Tx buffer isn't free, then the socket buffer is
 * deferred and the Tx queue is stopped so that the deferred socket buffer can
 * be transmitted when the Emaclite device is free to transmit data.
 *
 * Return:      0, always.
 */
static int xemaclite_send(struct sk_buff *orig_skb, struct net_device *dev)
{
        struct net_local *lp = netdev_priv(dev);
        struct sk_buff *new_skb;
        unsigned int len;
        unsigned long flags;

        len = orig_skb->len;

        new_skb = orig_skb;

        spin_lock_irqsave(&lp->reset_lock, flags);
        if (xemaclite_send_data(lp, (u8 *) new_skb->data, len) != 0) {
                /* If the Emaclite Tx buffer is busy, stop the Tx queue and
                 * defer the skb for transmission during the ISR, after the
                 * current transmission is complete */
                netif_stop_queue(dev);
                lp->deferred_skb = new_skb;
                /* Take the time stamp now, since we can't do this in an ISR. */
                skb_tx_timestamp(new_skb);
                spin_unlock_irqrestore(&lp->reset_lock, flags);
                return 0;
        }
        spin_unlock_irqrestore(&lp->reset_lock, flags);

        skb_tx_timestamp(new_skb);

        dev->stats.tx_bytes += len;
        dev_consume_skb_any(new_skb);

        return 0;
}

/**
 * get_bool - Get a parameter from the OF device
 * @ofdev:      Pointer to OF device structure
 * @s:          Property to be retrieved
 *
 * This function looks for a property in the device node and returns the value
 * of the property if its found or 0 if the property is not found.
 *
 * Return:      Value of the parameter if the parameter is found, or 0 otherwise
 */
static bool get_bool(struct platform_device *ofdev, const char *s)
{
        u32 *p = (u32 *)of_get_property(ofdev->dev.of_node, s, NULL);

        if (p) {
                return (bool)*p;
        } else {
                dev_warn(&ofdev->dev, "Parameter %s not found,"
                        "defaulting to false\n", s);
                return false;
        }
}

static const struct net_device_ops xemaclite_netdev_ops;

/**
 * xemaclite_of_probe - Probe method for the Emaclite device.
 * @ofdev:      Pointer to OF device structure
 * @match:      Pointer to the structure used for matching a device
 *
 * This function probes for the Emaclite device in the device tree.
 * It initializes the driver data structure and the hardware, sets the MAC
 * address and registers the network device.
 * It also registers a mii_bus for the Emaclite device, if MDIO is included
 * in the device.
 *
 * Return:      0, if the driver is bound to the Emaclite device, or
 *              a negative error if there is failure.
 */
static int xemaclite_of_probe(struct platform_device *ofdev)
{
        struct resource *res;
        struct net_device *ndev = NULL;
        struct net_local *lp = NULL;
        struct device *dev = &ofdev->dev;
        const void *mac_address;

        int rc = 0;

        dev_info(dev, "Device Tree Probing\n");

        /* Create an ethernet device instance */
        ndev = alloc_etherdev(sizeof(struct net_local));
        if (!ndev)
                return -ENOMEM;

        dev_set_drvdata(dev, ndev);
        SET_NETDEV_DEV(ndev, &ofdev->dev);

        lp = netdev_priv(ndev);
        lp->ndev = ndev;

        /* Get IRQ for the device */
        res = platform_get_resource(ofdev, IORESOURCE_IRQ, 0);
        if (!res) {
                dev_err(dev, "no IRQ found\n");
                rc = -ENXIO;
                goto error;
        }

        ndev->irq = res->start;

        res = platform_get_resource(ofdev, IORESOURCE_MEM, 0);
        lp->base_addr = devm_ioremap_resource(&ofdev->dev, res);
        if (IS_ERR(lp->base_addr)) {
                rc = PTR_ERR(lp->base_addr);
                goto error;
        }

        ndev->mem_start = res->start;
        ndev->mem_end = res->end;

        spin_lock_init(&lp->reset_lock);
        lp->next_tx_buf_to_use = 0x0;
        lp->next_rx_buf_to_use = 0x0;
        lp->tx_ping_pong = get_bool(ofdev, "xlnx,tx-ping-pong");
        lp->rx_ping_pong = get_bool(ofdev, "xlnx,rx-ping-pong");
        mac_address = of_get_mac_address(ofdev->dev.of_node);

        if (mac_address) {
                /* Set the MAC address. */
                memcpy(ndev->dev_addr, mac_address, ETH_ALEN);
        } else {
                dev_warn(dev, "No MAC address found, using random\n");
                eth_hw_addr_random(ndev);
        }

        /* Clear the Tx CSR's in case this is a restart */
        xemaclite_writel(0, lp->base_addr + XEL_TSR_OFFSET);
        xemaclite_writel(0, lp->base_addr + XEL_BUFFER_OFFSET + XEL_TSR_OFFSET);

        /* Set the MAC address in the EmacLite device */
        xemaclite_update_address(lp, ndev->dev_addr);

        lp->phy_node = of_parse_phandle(ofdev->dev.of_node, "phy-handle", 0);
        xemaclite_mdio_setup(lp, &ofdev->dev);

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

        ndev->netdev_ops = &xemaclite_netdev_ops;
        ndev->flags &= ~IFF_MULTICAST;
        ndev->watchdog_timeo = TX_TIMEOUT;

        /* Finally, register the device */
        rc = register_netdev(ndev);
        if (rc) {
                dev_err(dev,
                        "Cannot register network device, aborting\n");
                goto error;
        }

        dev_info(dev,
                 "Xilinx EmacLite at 0x%08X mapped to 0x%08X, irq=%d\n",
                 (unsigned int __force)ndev->mem_start,
                 (unsigned int __force)lp->base_addr, ndev->irq);
        return 0;

error:
        free_netdev(ndev);
        return rc;
}

/**
 * xemaclite_of_remove - Unbind the driver from the Emaclite device.
 * @of_dev:     Pointer to OF device structure
 *
 * This function is called if a device is physically removed from the system or
 * if the driver module is being unloaded. It frees any resources allocated to
 * the device.
 *
 * Return:      0, always.
 */
static int xemaclite_of_remove(struct platform_device *of_dev)
{
        struct net_device *ndev = platform_get_drvdata(of_dev);

        struct net_local *lp = netdev_priv(ndev);

        /* Un-register the mii_bus, if configured */
        if (lp->mii_bus) {
                mdiobus_unregister(lp->mii_bus);
                mdiobus_free(lp->mii_bus);
                lp->mii_bus = NULL;
        }

        unregister_netdev(ndev);

        of_node_put(lp->phy_node);
        lp->phy_node = NULL;

        free_netdev(ndev);

        return 0;
}

#ifdef CONFIG_NET_POLL_CONTROLLER
static void
xemaclite_poll_controller(struct net_device *ndev)
{
        disable_irq(ndev->irq);
        xemaclite_interrupt(ndev->irq, ndev);
        enable_irq(ndev->irq);
}
#endif

static const struct net_device_ops xemaclite_netdev_ops = {
        .ndo_open               = xemaclite_open,
        .ndo_stop               = xemaclite_close,
        .ndo_start_xmit         = xemaclite_send,
        .ndo_set_mac_address    = xemaclite_set_mac_address,
        .ndo_tx_timeout         = xemaclite_tx_timeout,
#ifdef CONFIG_NET_POLL_CONTROLLER
        .ndo_poll_controller = xemaclite_poll_controller,
#endif
};

/* Match table for OF platform binding */
static const struct of_device_id xemaclite_of_match[] = {
        { .compatible = "xlnx,opb-ethernetlite-1.01.a", },
        { .compatible = "xlnx,opb-ethernetlite-1.01.b", },
        { .compatible = "xlnx,xps-ethernetlite-1.00.a", },
        { .compatible = "xlnx,xps-ethernetlite-2.00.a", },
        { .compatible = "xlnx,xps-ethernetlite-2.01.a", },
        { .compatible = "xlnx,xps-ethernetlite-3.00.a", },
        { /* end of list */ },
};
MODULE_DEVICE_TABLE(of, xemaclite_of_match);

static struct platform_driver xemaclite_of_driver = {
        .driver = {
                .name = DRIVER_NAME,
                .of_match_table = xemaclite_of_match,
        },
        .probe          = xemaclite_of_probe,
        .remove         = xemaclite_of_remove,
};

module_platform_driver(xemaclite_of_driver);

MODULE_AUTHOR("Xilinx, Inc.");
MODULE_DESCRIPTION("Xilinx Ethernet MAC Lite driver");
MODULE_LICENSE("GPL");