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/* 8390.c: A general NS8390 ethernet driver core for linux. */

/*

        Written 1992-94 by Donald Becker.

        Copyright 1993 United States Government as represented by the

        Director, National Security Agency.

        This software may be used and distributed according to the terms

        of the GNU Public License, incorporated herein by reference.

        The author may be reached as becker@CESDIS.gsfc.nasa.gov, or C/O

        Center of Excellence in Space Data and Information Sciences

           Code 930.5, Goddard Space Flight Center, Greenbelt MD 20771

  This is the chip-specific code for many 8390-based ethernet adaptors.

  This is not a complete driver, it must be combined with board-specific

  code such as ne.c, wd.c, 3c503.c, etc.

  Seeing how at least eight drivers use this code, (not counting the

  PCMCIA ones either) it is easy to break some card by what seems like

  a simple innocent change. Please contact me or Donald if you think

  you have found something that needs changing. -- PG

  Changelog:

  Paul Gortmaker        : remove set_bit lock, other cleanups.

  Paul Gortmaker        : add ei_get_8390_hdr() so we can pass skb's to

                          ei_block_input() for eth_io_copy_and_sum().

  Paul Gortmaker        : exchange static int ei_pingpong for a #define,

                          also add better Tx error handling.

  Paul Gortmaker        : rewrite Rx overrun handling as per NS specs.

  Alexey Kuznetsov      : use the 8390's six bit hash multicast filter.

  Paul Gortmaker        : tweak ANK's above multicast changes a bit.

  Paul Gortmaker        : update packet statistics for v2.1.x

  Alan Cox              : support arbitary stupid port mappings on the

                          68K Macintosh. Support >16bit I/O spaces

  Paul Gortmaker        : add kmod support for auto-loading of the 8390

                          module by all drivers that require it.

  Alan Cox              : Spinlocking work, added 'BUG_83C690'

  Sources:

  The National Semiconductor LAN Databook, and the 3Com 3c503 databook.

  */

static const char *version =

    "8390.c:v1.10cvs 9/23/94 Donald Becker (becker@cesdis.gsfc.nasa.gov)\n";

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/sched.h>

#include <linux/fs.h>

#include <linux/types.h>

#include <linux/ptrace.h>

#include <linux/string.h>

#include <asm/system.h>

#include <asm/uaccess.h>

#include <asm/bitops.h>

#include <asm/io.h>

#include <asm/irq.h>

#include <linux/delay.h>

#include <linux/errno.h>

#include <linux/fcntl.h>

#include <linux/in.h>

#include <linux/interrupt.h>

#include <linux/init.h>

#include <linux/netdevice.h>

#include <linux/etherdevice.h>

#define NS8390_CORE

#include "8390.h"

#define BUG_83C690

/* These are the operational function interfaces to board-specific

   routines.

        void reset_8390(struct device *dev)

                Resets the board associated with DEV, including a hardware reset of

                the 8390.  This is only called when there is a transmit timeout, and

                it is always followed by 8390_init().

        void block_output(struct device *dev, int count, const unsigned char *buf,

                                          int start_page)

                Write the COUNT bytes of BUF to the packet buffer at START_PAGE.  The

                "page" value uses the 8390's 256-byte pages.

        void get_8390_hdr(struct device *dev, struct e8390_hdr *hdr, int ring_page)

                Read the 4 byte, page aligned 8390 header. *If* there is a

                subsequent read, it will be of the rest of the packet.

        void block_input(struct device *dev, int count, struct sk_buff *skb, int ring_offset)

                Read COUNT bytes from the packet buffer into the skb data area. Start

                reading from RING_OFFSET, the address as the 8390 sees it.  This will always

                follow the read of the 8390 header.

*/

#define ei_reset_8390 (ei_local->reset_8390)

#define ei_block_output (ei_local->block_output)

#define ei_block_input (ei_local->block_input)

#define ei_get_8390_hdr (ei_local->get_8390_hdr)

/* use 0 for production, 1 for verification, >2 for debug */

//#define VERBOSE_ERROR_DUMP

#ifndef ei_debug

int ei_debug = 0;

#endif

/* Index to functions. */

static void ei_tx_intr(struct device *dev);

static void ei_tx_err(struct device *dev);

static void ei_receive(struct device *dev);

static void ei_rx_overrun(struct device *dev);

/* Routines generic to NS8390-based boards. */

static void NS8390_trigger_send(struct device *dev, unsigned int length,

                                                                int start_page);

static void set_multicast_list(struct device *dev);

static void do_set_multicast_list(struct device *dev);

/*

 *      SMP and the 8390 setup.

 *

 *      The 8390 isnt exactly designed to be multithreaded on RX/TX. There is

 *      a page register that controls bank and packet buffer access. We guard

 *      this with ei_local->page_lock. Nobody should assume or set the page other

 *      than zero when the lock is not held. Lock holders must restore page 0

 *      before unlocking. Even pure readers must take the lock to protect in

 *      page 0.

 *

 *      To make life difficult the chip can also be very slow. We therefore can't

 *      just use spinlocks. For the longer lockups we disable the irq the device

 *      sits on and hold the lock. We must hold the lock because there is a dual

 *      processor case other than interrupts (get stats/set multicast list in

 *      parallel with each other and transmit).

 *

 *      Note: in theory we can just disable the irq on the card _but_ there is

 *      a latency on SMP irq delivery. So we can easily go "disable irq" "sync irqs"

 *      enter lock, take the queued irq. So we waddle instead of flying.

 *

 *      Finally by special arrangement for the purpose of being generally

 *      annoying the transmit function is called bh atomic. That places

 *      restrictions on the user context callers as disable_irq won't save

 *      them.

 */

/* Open/initialize the board.  This routine goes all-out, setting everything

   up anew at each open, even though many of these registers should only

   need to be set once at boot.

   */

int ei_open(struct device *dev)

{

        unsigned long flags;

        struct ei_device *ei_local = (struct ei_device *) dev->priv;

        /* This can't happen unless somebody forgot to call ethdev_init(). */

        if (ei_local == NULL)

        {

                printk(KERN_EMERG "%s: ei_open passed a non-existent device!\n", dev->name);

                return -ENXIO;

        }

        /*

         *      Grab the page lock so we own the register set, then call

         *      the init function.

         */

        spin_lock_irqsave(&ei_local->page_lock, flags);

        NS8390_init(dev, 1);

        /* Set the flag before we drop the lock, That way the IRQ arrives

           after its set and we get no silly warnings */

        dev->start = 1;

        spin_unlock_irqrestore(&ei_local->page_lock, flags);

        ei_local->irqlock = 0;

        return 0;

}

/* Opposite of above. Only used when "ifconfig <devname> down" is done. */

int ei_close(struct device *dev)

{

        struct ei_device *ei_local = (struct ei_device *) dev->priv;

        unsigned long flags;

        /*

         *      Hold the page lock during close

         */

        spin_lock_irqsave(&ei_local->page_lock, flags);

        NS8390_init(dev, 0);

        spin_unlock_irqrestore(&ei_local->page_lock, flags);

        dev->start = 0;

        return 0;

}

static int ei_start_xmit(struct sk_buff *skb, struct device *dev)

{

        long e8390_base = dev->base_addr;

        struct ei_device *ei_local = (struct ei_device *) dev->priv;

        int length, send_length, output_page;

        unsigned long flags;

        /*

         *  We normally shouldn't be called if dev->tbusy is set, but the

         *  existing code does anyway. If it has been too long since the

         *  last Tx, we assume the board has died and kick it. We are

         *  bh_atomic here.

         */

        if (dev->tbusy)

        {       /* Do timeouts, just like the 8003 driver. */

                int txsr;

                int isr;

                int tickssofar = jiffies - dev->trans_start;

                /*

                 *      Need the page lock. Now see what went wrong. This bit is

                 *      fast.

                 */

                spin_lock_irqsave(&ei_local->page_lock, flags);

                txsr = inb(e8390_base+EN0_TSR);

                if (tickssofar < TX_TIMEOUT ||  (tickssofar < (TX_TIMEOUT+5) && ! (txsr & ENTSR_PTX)))

                {

                        spin_unlock_irqrestore(&ei_local->page_lock, flags);

                        return 1;

                }

                ei_local->stat.tx_errors++;

                isr = inb(e8390_base+EN0_ISR);

                if (dev->start == 0)

                {

                        spin_unlock_irqrestore(&ei_local->page_lock, flags);

                        printk(KERN_WARNING "%s: xmit on stopped card\n", dev->name);

                        return 1;

                }

                /*

                 * Note that if the Tx posted a TX_ERR interrupt, then the

                 * error will have been handled from the interrupt handler

                 * and not here. Error statistics are handled there as well.

                 */

                printk(KERN_DEBUG "%s: Tx timed out, %s TSR=%#2x, ISR=%#2x, t=%d.\n",

                        dev->name, (txsr & ENTSR_ABT) ? "excess collisions." :

                        (isr) ? "lost interrupt?" : "cable problem?", txsr, isr, tickssofar);

                if (!isr && !ei_local->stat.tx_packets)

                {

                        /* The 8390 probably hasn't gotten on the cable yet. */

                        ei_local->interface_num ^= 1;   /* Try a different xcvr.  */

                }

                /*

                 *      Play shuffle the locks, a reset on some chips takes a few

                 *      mS. We very rarely hit this point.

                 */

                spin_unlock_irqrestore(&ei_local->page_lock, flags);

                /* Ugly but a reset can be slow, yet must be protected */

                disable_irq_nosync(dev->irq);

                spin_lock(&ei_local->page_lock);

                /* Try to restart the card.  Perhaps the user has fixed something. */

                ei_reset_8390(dev);

                NS8390_init(dev, 1);

                spin_unlock(&ei_local->page_lock);

                enable_irq(dev->irq);

                dev->trans_start = jiffies;

        }

        length = skb->len;

        /* Mask interrupts from the ethercard.

           SMP: We have to grab the lock here otherwise the IRQ handler

           on another CPU can flip window and race the IRQ mask set. We end

           up trashing the mcast filter not disabling irqs if we dont lock */

        spin_lock_irqsave(&ei_local->page_lock, flags);

        outb_p(0x00, e8390_base + EN0_IMR);

        spin_unlock_irqrestore(&ei_local->page_lock, flags);

        /*

         *      Slow phase with lock held.

         */

        disable_irq_nosync(dev->irq);

        spin_lock(&ei_local->page_lock);

        if (dev->interrupt)

        {

                printk(KERN_WARNING "%s: Tx request while isr active.\n",dev->name);

                outb_p(ENISR_ALL, e8390_base + EN0_IMR);

                spin_unlock(&ei_local->page_lock);

                enable_irq(dev->irq);

                ei_local->stat.tx_errors++;

                dev_kfree_skb(skb);

                return 0;

        }

        ei_local->irqlock = 1;

        send_length = ETH_ZLEN < length ? length : ETH_ZLEN;

#ifdef EI_PINGPONG

        /*

         * We have two Tx slots available for use. Find the first free

         * slot, and then perform some sanity checks. With two Tx bufs,

         * you get very close to transmitting back-to-back packets. With

         * only one Tx buf, the transmitter sits idle while you reload the

         * card, leaving a substantial gap between each transmitted packet.

         */

        if (ei_local->tx1 == 0)

        {

                output_page = ei_local->tx_start_page;

                ei_local->tx1 = send_length;

                if (ei_debug  &&  ei_local->tx2 > 0)

                        printk(KERN_DEBUG "%s: idle transmitter tx2=%d, lasttx=%d, txing=%d.\n",

                                dev->name, ei_local->tx2, ei_local->lasttx, ei_local->txing);

        }

        else if (ei_local->tx2 == 0)

        {

                output_page = ei_local->tx_start_page + TX_1X_PAGES;

                ei_local->tx2 = send_length;

                if (ei_debug  &&  ei_local->tx1 > 0)

                        printk(KERN_DEBUG "%s: idle transmitter, tx1=%d, lasttx=%d, txing=%d.\n",

                                dev->name, ei_local->tx1, ei_local->lasttx, ei_local->txing);

        }

        else

        {       /* We should never get here. */

                if (ei_debug)

                        printk(KERN_DEBUG "%s: No Tx buffers free! irq=%ld tx1=%d tx2=%d last=%d\n",

                                dev->name, dev->interrupt, ei_local->tx1, ei_local->tx2, ei_local->lasttx);

                ei_local->irqlock = 0;

                dev->tbusy = 1;

                outb_p(ENISR_ALL, e8390_base + EN0_IMR);

                spin_unlock(&ei_local->page_lock);

                enable_irq(dev->irq);

                ei_local->stat.tx_errors++;

                return 1;

        }

        /*

         * Okay, now upload the packet and trigger a send if the transmitter

         * isn't already sending. If it is busy, the interrupt handler will

         * trigger the send later, upon receiving a Tx done interrupt.

         */

        ei_block_output(dev, length, skb->data, output_page);

        if (! ei_local->txing)

        {

                ei_local->txing = 1;

                NS8390_trigger_send(dev, send_length, output_page);

                dev->trans_start = jiffies;

                if (output_page == ei_local->tx_start_page)

                {

                        ei_local->tx1 = -1;

                        ei_local->lasttx = -1;

                }

                else

                {

                        ei_local->tx2 = -1;

                        ei_local->lasttx = -2;

                }

        }

        else ei_local->txqueue++;

        dev->tbusy = (ei_local->tx1  &&  ei_local->tx2);

#else   /* EI_PINGPONG */

        /*

         * Only one Tx buffer in use. You need two Tx bufs to come close to

         * back-to-back transmits. Expect a 20 -> 25% performance hit on

         * reasonable hardware if you only use one Tx buffer.

         */

        ei_block_output(dev, length, skb->data, ei_local->tx_start_page);

        ei_local->txing = 1;

        NS8390_trigger_send(dev, send_length, ei_local->tx_start_page);

        dev->trans_start = jiffies;

        dev->tbusy = 1;

#endif  /* EI_PINGPONG */

        /* Turn 8390 interrupts back on. */

        ei_local->irqlock = 0;

        outb_p(ENISR_ALL, e8390_base + EN0_IMR);

        spin_unlock(&ei_local->page_lock);

        enable_irq(dev->irq);

        dev_kfree_skb (skb);

        ei_local->stat.tx_bytes += send_length;

        return 0;

}

/* The typical workload of the driver:

   Handle the ether interface interrupts. */

void ei_interrupt(int irq, void *dev_id, struct pt_regs * regs)

{

        struct device *dev = dev_id;

        long e8390_base;

        int interrupts, nr_serviced = 0;

        struct ei_device *ei_local;

        if (dev == NULL)

        {

                printk ("net_interrupt(): irq %d for unknown device.\n", irq);

                return;

        }

        e8390_base = dev->base_addr;

        ei_local = (struct ei_device *) dev->priv;

        /*

         *      Protect the irq test too.

         */

        spin_lock(&ei_local->page_lock);

        if (dev->interrupt || ei_local->irqlock)

        {

#if 1 /* This might just be an interrupt for a PCI device sharing this line */

                /* The "irqlock" check is only for testing. */

                printk(ei_local->irqlock

                           ? "%s: Interrupted while interrupts are masked! isr=%#2x imr=%#2x.\n"

                           : "%s: Reentering the interrupt handler! isr=%#2x imr=%#2x.\n",

                           dev->name, inb_p(e8390_base + EN0_ISR),

                           inb_p(e8390_base + EN0_IMR));

#endif

                spin_unlock(&ei_local->page_lock);

                return;

        }

        dev->interrupt = 1;

        /* Change to page 0 and read the intr status reg. */

        outb_p(E8390_NODMA+E8390_PAGE0, e8390_base + E8390_CMD);

        if (ei_debug > 3)

                printk(KERN_DEBUG "%s: interrupt(isr=%#2.2x).\n", dev->name,

                           inb_p(e8390_base + EN0_ISR));

        /* !!Assumption!! -- we stay in page 0.  Don't break this. */

        while ((interrupts = inb_p(e8390_base + EN0_ISR)) != 0

                   && ++nr_serviced < MAX_SERVICE)

        {

                if (dev->start == 0)

                {

                        printk(KERN_WARNING "%s: interrupt from stopped card\n", dev->name);

                        interrupts = 0;

                        break;

                }

                if (interrupts & ENISR_OVER)

                        ei_rx_overrun(dev);

                else if (interrupts & (ENISR_RX+ENISR_RX_ERR))

                {

                        /* Got a good (?) packet. */

                        ei_receive(dev);

                }

                /* Push the next to-transmit packet through. */

                if (interrupts & ENISR_TX)

                        ei_tx_intr(dev);

                else if (interrupts & ENISR_TX_ERR)

                        ei_tx_err(dev);

                if (interrupts & ENISR_COUNTERS)

                {

                        ei_local->stat.rx_frame_errors += inb_p(e8390_base + EN0_COUNTER0);

                        ei_local->stat.rx_crc_errors   += inb_p(e8390_base + EN0_COUNTER1);

                        ei_local->stat.rx_missed_errors+= inb_p(e8390_base + EN0_COUNTER2);

                        outb_p(ENISR_COUNTERS, e8390_base + EN0_ISR); /* Ack intr. */

                }

                /* Ignore any RDC interrupts that make it back to here. */

                if (interrupts & ENISR_RDC)

                {

                        outb_p(ENISR_RDC, e8390_base + EN0_ISR);

                }

                outb_p(E8390_NODMA+E8390_PAGE0+E8390_START, e8390_base + E8390_CMD);

        }

        if (interrupts && ei_debug)

        {

                outb_p(E8390_NODMA+E8390_PAGE0+E8390_START, e8390_base + E8390_CMD);

                if (nr_serviced >= MAX_SERVICE)

                {

                        printk(KERN_WARNING "%s: Too much work at interrupt, status %#2.2x\n",

                                   dev->name, interrupts);

                        outb_p(ENISR_ALL, e8390_base + EN0_ISR); /* Ack. most intrs. */

                } else {

                        printk(KERN_WARNING "%s: unknown interrupt %#2x\n", dev->name, interrupts);

                        outb_p(0xff, e8390_base + EN0_ISR); /* Ack. all intrs. */

                }

        }

        dev->interrupt = 0;

        spin_unlock(&ei_local->page_lock);

        return;

}

/*

 * A transmitter error has happened. Most likely excess collisions (which

 * is a fairly normal condition). If the error is one where the Tx will

 * have been aborted, we try and send another one right away, instead of

 * letting the failed packet sit and collect dust in the Tx buffer. This

 * is a much better solution as it avoids kernel based Tx timeouts, and

 * an unnecessary card reset.

 *

 * Called with lock held

 */

static void ei_tx_err(struct device *dev)

{

        long e8390_base = dev->base_addr;

        struct ei_device *ei_local = (struct ei_device *) dev->priv;

        unsigned char txsr = inb_p(e8390_base+EN0_TSR);

        unsigned char tx_was_aborted = txsr & (ENTSR_ABT+ENTSR_FU);

#ifdef VERBOSE_ERROR_DUMP

        printk(KERN_DEBUG "%s: transmitter error (%#2x): ", dev->name, txsr);

        if (txsr & ENTSR_ABT)

                printk("excess-collisions ");

        if (txsr & ENTSR_ND)

                printk("non-deferral ");

        if (txsr & ENTSR_CRS)

                printk("lost-carrier ");

        if (txsr & ENTSR_FU)

                printk("FIFO-underrun ");

        if (txsr & ENTSR_CDH)

                printk("lost-heartbeat ");

        printk("\n");

#endif

        outb_p(ENISR_TX_ERR, e8390_base + EN0_ISR); /* Ack intr. */

        if (tx_was_aborted)

                ei_tx_intr(dev);

        else

        {

                ei_local->stat.tx_errors++;

                if (txsr & ENTSR_CRS) ei_local->stat.tx_carrier_errors++;

                if (txsr & ENTSR_CDH) ei_local->stat.tx_heartbeat_errors++;

                if (txsr & ENTSR_OWC) ei_local->stat.tx_window_errors++;

        }

}

/* We have finished a transmit: check for errors and then trigger the next

   packet to be sent. Called with lock held */

static void ei_tx_intr(struct device *dev)

{

        long e8390_base = dev->base_addr;

        struct ei_device *ei_local = (struct ei_device *) dev->priv;

        int status = inb(e8390_base + EN0_TSR);

        outb_p(ENISR_TX, e8390_base + EN0_ISR); /* Ack intr. */

#ifdef EI_PINGPONG

        /*

         * There are two Tx buffers, see which one finished, and trigger

         * the send of another one if it exists.

         */

        ei_local->txqueue--;

        if (ei_local->tx1 < 0)

        {

                if (ei_local->lasttx != 1 && ei_local->lasttx != -1)

                        printk(KERN_ERR "%s: bogus last_tx_buffer %d, tx1=%d.\n",

                                ei_local->name, ei_local->lasttx, ei_local->tx1);

                ei_local->tx1 = 0;

                dev->tbusy = 0;

                if (ei_local->tx2 > 0)

                {

                        ei_local->txing = 1;

                        NS8390_trigger_send(dev, ei_local->tx2, ei_local->tx_start_page + 6);

                        dev->trans_start = jiffies;

                        ei_local->tx2 = -1,

                        ei_local->lasttx = 2;

                }

                else ei_local->lasttx = 20, ei_local->txing = 0;       

        }

        else if (ei_local->tx2 < 0)

        {

                if (ei_local->lasttx != 2  &&  ei_local->lasttx != -2)

                        printk("%s: bogus last_tx_buffer %d, tx2=%d.\n",

                                ei_local->name, ei_local->lasttx, ei_local->tx2);

                ei_local->tx2 = 0;

                dev->tbusy = 0;

                if (ei_local->tx1 > 0)

                {

                        ei_local->txing = 1;

                        NS8390_trigger_send(dev, ei_local->tx1, ei_local->tx_start_page);

                        dev->trans_start = jiffies;

                        ei_local->tx1 = -1;

                        ei_local->lasttx = 1;

                }

                else

                        ei_local->lasttx = 10, ei_local->txing = 0;

        }

        else printk(KERN_WARNING "%s: unexpected TX-done interrupt, lasttx=%d.\n",

                        dev->name, ei_local->lasttx);

#else   /* EI_PINGPONG */

        /*

         *  Single Tx buffer: mark it free so another packet can be loaded.

         */

        ei_local->txing = 0;

        dev->tbusy = 0;

#endif

        /* Minimize Tx latency: update the statistics after we restart TXing. */

        if (status & ENTSR_COL)

                ei_local->stat.collisions++;

        if (status & ENTSR_PTX)

                ei_local->stat.tx_packets++;

        else

        {

                ei_local->stat.tx_errors++;

                if (status & ENTSR_ABT)

                {

                        ei_local->stat.tx_aborted_errors++;

                        ei_local->stat.collisions += 16;

                }

                if (status & ENTSR_CRS)

                        ei_local->stat.tx_carrier_errors++;

                if (status & ENTSR_FU)

                        ei_local->stat.tx_fifo_errors++;

                if (status & ENTSR_CDH)

                        ei_local->stat.tx_heartbeat_errors++;

                if (status & ENTSR_OWC)

                        ei_local->stat.tx_window_errors++;

        }

        mark_bh (NET_BH);

}

/* We have a good packet(s), get it/them out of the buffers.

   Called with lock held */

static void ei_receive(struct device *dev)

{

        long e8390_base = dev->base_addr;

        struct ei_device *ei_local = (struct ei_device *) dev->priv;

        unsigned char rxing_page, this_frame, next_frame;

        unsigned short current_offset;

        int rx_pkt_count = 0;

        struct e8390_pkt_hdr rx_frame;

        int num_rx_pages = ei_local->stop_page-ei_local->rx_start_page;

        while (++rx_pkt_count < 10)

        {

                int pkt_len, pkt_stat;

                /* Get the rx page (incoming packet pointer). */

                outb_p(E8390_NODMA+E8390_PAGE1, e8390_base + E8390_CMD);

                rxing_page = inb_p(e8390_base + EN1_CURPAG);

                outb_p(E8390_NODMA+E8390_PAGE0, e8390_base + E8390_CMD);

                /* Remove one frame from the ring.  Boundary is always a page behind. */

                this_frame = inb_p(e8390_base + EN0_BOUNDARY) + 1;

                if (this_frame >= ei_local->stop_page)

                        this_frame = ei_local->rx_start_page;

                /* Someday we'll omit the previous, iff we never get this message.

                   (There is at least one clone claimed to have a problem.)  */

                if (ei_debug > 0  &&  this_frame != ei_local->current_page)

                        printk(KERN_ERR "%s: mismatched read page pointers %2x vs %2x.\n",

                                   dev->name, this_frame, ei_local->current_page);

                if (this_frame == rxing_page)   /* Read all the frames? */

                        break;                          /* Done for now */

                current_offset = this_frame << 8;

                ei_get_8390_hdr(dev, &rx_frame, this_frame);

                pkt_len = rx_frame.count - sizeof(struct e8390_pkt_hdr);

                pkt_stat = rx_frame.status;

                next_frame = this_frame + 1 + ((pkt_len+4)>>8);

                /* Check for bogosity warned by 3c503 book: the status byte is never

                   written.  This happened a lot during testing! This code should be

                   cleaned up someday. */

                if (rx_frame.next != next_frame

                        && rx_frame.next != next_frame + 1

                        && rx_frame.next != next_frame - num_rx_pages

                        && rx_frame.next != next_frame + 1 - num_rx_pages) {

                        ei_local->current_page = rxing_page;

                        outb(ei_local->current_page-1, e8390_base+EN0_BOUNDARY);

                        ei_local->stat.rx_errors++;

                        continue;

                }

                if (pkt_len < 60  ||  pkt_len > 1518)

                {

                        if (ei_debug)

                                printk(KERN_DEBUG "%s: bogus packet size: %d, status=%#2x nxpg=%#2x.\n",

                                           dev->name, rx_frame.count, rx_frame.status,

                                           rx_frame.next);

                        ei_local->stat.rx_errors++;

                        ei_local->stat.rx_length_errors++;

                }

                 else if ((pkt_stat & 0x0F) == ENRSR_RXOK)

                {

                        struct sk_buff *skb;

                        skb = dev_alloc_skb(pkt_len+2);

                        if (skb == NULL)

                        {

                                if (ei_debug > 1)

                                        printk(KERN_DEBUG "%s: Couldn't allocate a sk_buff of size %d.\n",

                                                   dev->name, pkt_len);

                                ei_local->stat.rx_dropped++;

                                break;

                        }

                        else

                        {

                                skb_reserve(skb,2);     /* IP headers on 16 byte boundaries */

                                skb->dev = dev;

                                skb_put(skb, pkt_len);  /* Make room */

                                ei_block_input(dev, pkt_len, skb, current_offset + sizeof(rx_frame));

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

                                netif_rx(skb);

                                ei_local->stat.rx_packets++;

                                ei_local->stat.rx_bytes += pkt_len;

                                if (pkt_stat & ENRSR_PHY)

                                        ei_local->stat.multicast++;

                        }

                }

                else

                {

                        if (ei_debug)

                                printk(KERN_DEBUG "%s: bogus packet: status=%#2x nxpg=%#2x size=%d\n",

                                           dev->name, rx_frame.status, rx_frame.next,

                                           rx_frame.count);

                        ei_local->stat.rx_errors++;

                        /* NB: The NIC counts CRC, frame and missed errors. */

                        if (pkt_stat & ENRSR_FO)

                                ei_local->stat.rx_fifo_errors++;

                }

                next_frame = rx_frame.next;

                /* This _should_ never happen: it's here for avoiding bad clones. */

                if (next_frame >= ei_local->stop_page) {

                        printk("%s: next frame inconsistency, %#2x\n", dev->name,

                                   next_frame);

                        next_frame = ei_local->rx_start_page;

                }

                ei_local->current_page = next_frame;

                outb_p(next_frame-1, e8390_base+EN0_BOUNDARY);

        }

        /* We used to also ack ENISR_OVER here, but that would sometimes mask

           a real overrun, leaving the 8390 in a stopped state with rec'vr off. */

        outb_p(ENISR_RX+ENISR_RX_ERR, e8390_base+EN0_ISR);

        return;

}

/*

 * We have a receiver overrun: we have to kick the 8390 to get it started

 * again. Problem is that you have to kick it exactly as NS prescribes in

 * the updated datasheets, or "the NIC may act in an unpredictable manner."

 * This includes causing "the NIC to defer indefinitely when it is stopped

 * on a busy network."  Ugh.

 * Called with lock held. Don't call this with the interrupts off or your

 * computer will hate you - it takes 10mS or so.

 */

static void ei_rx_overrun(struct device *dev)

{

        long e8390_base = dev->base_addr;

        unsigned char was_txing, must_resend = 0;

        struct ei_device *ei_local = (struct ei_device *) dev->priv;

        /*

         * Record whether a Tx was in progress and then issue the

         * stop command.

         */

        was_txing = inb_p(e8390_base+E8390_CMD) & E8390_TRANS;

        outb_p(E8390_NODMA+E8390_PAGE0+E8390_STOP, e8390_base+E8390_CMD);

        if (ei_debug > 1)

                printk(KERN_DEBUG "%s: Receiver overrun.\n", dev->name);

        ei_local->stat.rx_over_errors++;

        /*

         * Wait a full Tx time (1.2ms) + some guard time, NS says 1.6ms total.

         * Early datasheets said to poll the reset bit, but now they say that

         * it "is not a reliable indicator and subsequently should be ignored."

         * We wait at least 10ms.

         */

        udelay(10*1000);

        /*

         * Reset RBCR[01] back to zero as per magic incantation.

         */

        outb_p(0x00, e8390_base+EN0_RCNTLO);

        outb_p(0x00, e8390_base+EN0_RCNTHI);

        /*

         * See if any Tx was interrupted or not. According to NS, this

         * step is vital, and skipping it will cause no end of havoc.

         */

        if (was_txing)

        {

                unsigned char tx_completed = inb_p(e8390_base+EN0_ISR) & (ENISR_TX+ENISR_TX_ERR);

                if (!tx_completed)

                        must_resend = 1;

        }

        /*

         * Have to enter loopback mode and then restart the NIC before

         * you are allowed to slurp packets up off the ring.

         */

        outb_p(E8390_TXOFF, e8390_base + EN0_TXCR);

        outb_p(E8390_NODMA + E8390_PAGE0 + E8390_START, e8390_base + E8390_CMD);