/*      $OpenBSD: dp8390.c,v 1.63 2022/01/09 05:42:38 jsg Exp $ */
/*      $NetBSD: dp8390.c,v 1.13 1998/07/05 06:49:11 jonathan Exp $     */

/*
 * Device driver for National Semiconductor DS8390/WD83C690 based ethernet
 * adapters.
 *
 * Copyright (c) 1994, 1995 Charles M. Hannum.  All rights reserved.
 *
 * Copyright (C) 1993, David Greenman.  This software may be used, modified,
 * copied, distributed, and sold, in both source and binary form provided that
 * the above copyright and these terms are retained.  Under no circumstances is
 * the author responsible for the proper functioning of this software, nor does
 * the author assume any responsibility for damages incurred with its use.
 */

#include "bpfilter.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/device.h>
#include <sys/errno.h>
#include <sys/ioctl.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/syslog.h>

#include <net/if.h>
#include <net/if_media.h>

#include <netinet/in.h>
#include <netinet/if_ether.h>

#if NBPFILTER > 0
#include <net/bpf.h>
#endif

#include <machine/bus.h>

#include <dev/ic/dp8390reg.h>
#include <dev/ic/dp8390var.h>

#ifdef DEBUG
#define __inline__      /* XXX for debugging porpoises */
#endif

static __inline__ void  dp8390_xmit(struct dp8390_softc *);

static __inline__ void  dp8390_read_hdr(struct dp8390_softc *,
                            int, struct dp8390_ring *);
static __inline__ int   dp8390_ring_copy(struct dp8390_softc *,
                            int, caddr_t, u_short);
static __inline__ int   dp8390_write_mbuf(struct dp8390_softc *,
                            struct mbuf *, int);

static int              dp8390_test_mem(struct dp8390_softc *);

#ifdef DEBUG
int     dp8390_debug = 0;
#endif

/*
 * Standard media init routine for the dp8390.
 */
void
dp8390_media_init(struct dp8390_softc *sc)
{
        ifmedia_init(&sc->sc_media, 0, dp8390_mediachange, dp8390_mediastatus);
        ifmedia_add(&sc->sc_media, IFM_ETHER|IFM_MANUAL, 0, NULL);
        ifmedia_set(&sc->sc_media, IFM_ETHER|IFM_MANUAL);
}

/*
 * Do bus-independent setup.
 */
int
dp8390_config(struct dp8390_softc *sc)
{
        struct ifnet *ifp = &sc->sc_arpcom.ac_if;
        int rv;

        rv = 1;

        if (!sc->test_mem)
                sc->test_mem = dp8390_test_mem;

        /* Allocate one xmit buffer if < 16k, two buffers otherwise. */
        if ((sc->mem_size < 16384) ||
            (sc->sc_flags & DP8390_NO_MULTI_BUFFERING))
                sc->txb_cnt = 1;
        else if (sc->mem_size < 8192 * 3)
                sc->txb_cnt = 2;
        else
                sc->txb_cnt = 3;

        sc->tx_page_start = sc->mem_start >> ED_PAGE_SHIFT;
        sc->rec_page_start = sc->tx_page_start + sc->txb_cnt * ED_TXBUF_SIZE;
        sc->rec_page_stop = sc->tx_page_start + (sc->mem_size >> ED_PAGE_SHIFT);
        sc->mem_ring = sc->mem_start +
            ((sc->txb_cnt * ED_TXBUF_SIZE) << ED_PAGE_SHIFT);
        sc->mem_end = sc->mem_start + sc->mem_size;

        /* Now zero memory and verify that it is clear. */
        if ((*sc->test_mem)(sc))
                goto out;

        /* Set interface to stopped condition (reset). */
        dp8390_stop(sc);

        /* Initialize ifnet structure. */
        bcopy(sc->sc_dev.dv_xname, ifp->if_xname, IFNAMSIZ);
        ifp->if_softc = sc;
        ifp->if_start = dp8390_start;
        ifp->if_ioctl = dp8390_ioctl;
        if (!ifp->if_watchdog)
                ifp->if_watchdog = dp8390_watchdog;
        ifp->if_flags =
            IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;

        ifp->if_capabilities = IFCAP_VLAN_MTU;

        /* Print additional info when attached. */
        printf(", address %s\n", ether_sprintf(sc->sc_arpcom.ac_enaddr));

        /* Initialize media goo. */
        (*sc->sc_media_init)(sc);

        /* Attach the interface. */
        if_attach(ifp);
        ether_ifattach(ifp);

        rv = 0;
out:
        return (rv);
}

/*
 * Media change callback.
 */
int
dp8390_mediachange(struct ifnet *ifp)
{
        struct dp8390_softc *sc = ifp->if_softc;

        if (sc->sc_mediachange)
                return ((*sc->sc_mediachange)(sc));

        return (0);
}

/*
 * Media status callback.
 */
void
dp8390_mediastatus(struct ifnet *ifp, struct ifmediareq *ifmr)
{
        struct dp8390_softc *sc = ifp->if_softc;

        if (sc->sc_enabled == 0) {
                ifmr->ifm_active = IFM_ETHER | IFM_NONE;
                ifmr->ifm_status = 0;
                return;
        }

        if (sc->sc_mediastatus)
                (*sc->sc_mediastatus)(sc, ifmr);
}

/*
 * Reset interface.
 */
void
dp8390_reset(struct dp8390_softc *sc)
{
        int     s;

        s = splnet();
        dp8390_stop(sc);
        dp8390_init(sc);
        splx(s);
}

/*
 * Take interface offline.
 */
void
dp8390_stop(struct dp8390_softc *sc)
{
        bus_space_tag_t regt = sc->sc_regt;
        bus_space_handle_t regh = sc->sc_regh;
        int n = 5000;

        /* Stop everything on the interface, and select page 0 registers. */
        NIC_BARRIER(regt, regh);
        NIC_PUT(regt, regh, ED_P0_CR,
            sc->cr_proto | ED_CR_PAGE_0 | ED_CR_STP);
        NIC_BARRIER(regt, regh);

        /*
         * Wait for interface to enter stopped state, but limit # of checks to
         * 'n' (about 5ms).  It shouldn't even take 5us on modern DS8390's, but
         * just in case it's an old one.
         */
        while (((NIC_GET(regt, regh,
            ED_P0_ISR) & ED_ISR_RST) == 0) && --n)
                DELAY(1);

        if (sc->stop_card != NULL)
                (*sc->stop_card)(sc);
}

/*
 * Device timeout/watchdog routine.  Entered if the device neglects to generate
 * an interrupt after a transmit has been started on it.
 */

void
dp8390_watchdog(struct ifnet *ifp)
{
        struct dp8390_softc *sc = ifp->if_softc;

        log(LOG_ERR, "%s: device timeout\n", sc->sc_dev.dv_xname);
        ++sc->sc_arpcom.ac_if.if_oerrors;

        dp8390_reset(sc);
}

/*
 * Initialize device.
 */
void
dp8390_init(struct dp8390_softc *sc)
{
        bus_space_tag_t regt = sc->sc_regt;
        bus_space_handle_t regh = sc->sc_regh;
        struct ifnet *ifp = &sc->sc_arpcom.ac_if;
        u_int8_t mcaf[8];
        int i;

        /*
         * Initialize the NIC in the exact order outlined in the NS manual.
         * This init procedure is "mandatory"...don't change what or when
         * things happen.
         */

        /* Reset transmitter flags. */
        ifp->if_timer = 0;

        sc->txb_inuse = 0;
        sc->txb_new = 0;
        sc->txb_next_tx = 0;

        /* Set interface for page 0, remote DMA complete, stopped. */
        NIC_BARRIER(regt, regh);
        NIC_PUT(regt, regh, ED_P0_CR,
            sc->cr_proto | ED_CR_PAGE_0 | ED_CR_STP);
        NIC_BARRIER(regt, regh);

        if (sc->dcr_reg & ED_DCR_LS) {
                NIC_PUT(regt, regh, ED_P0_DCR, sc->dcr_reg);
        } else {
                /*
                 * Set FIFO threshold to 8, No auto-init Remote DMA, byte
                 * order=80x86, byte-wide DMA xfers,
                 */
                NIC_PUT(regt, regh, ED_P0_DCR, ED_DCR_FT1 | ED_DCR_LS);
        }

        /* Clear remote byte count registers. */
        NIC_PUT(regt, regh, ED_P0_RBCR0, 0);
        NIC_PUT(regt, regh, ED_P0_RBCR1, 0);

        /* Tell RCR to do nothing for now. */
        NIC_PUT(regt, regh, ED_P0_RCR, ED_RCR_MON | sc->rcr_proto);

        /* Place NIC in internal loopback mode. */
        NIC_PUT(regt, regh, ED_P0_TCR, ED_TCR_LB0);

        /* Set lower bits of byte addressable framing to 0. */
        if (sc->is790)
                NIC_PUT(regt, regh, 0x09, 0);

        /* Initialize receive buffer ring. */
        NIC_PUT(regt, regh, ED_P0_BNRY, sc->rec_page_start);
        NIC_PUT(regt, regh, ED_P0_PSTART, sc->rec_page_start);
        NIC_PUT(regt, regh, ED_P0_PSTOP, sc->rec_page_stop);

        /*
         * Enable the following interrupts: receive/transmit complete,
         * receive/transmit error, and Receiver OverWrite.
         *
         * Counter overflow and Remote DMA complete are *not* enabled.
         */
        NIC_PUT(regt, regh, ED_P0_IMR,
            ED_IMR_PRXE | ED_IMR_PTXE | ED_IMR_RXEE | ED_IMR_TXEE |
            ED_IMR_OVWE);

        /*
         * Clear all interrupts.  A '1' in each bit position clears the
         * corresponding flag.
         */
        NIC_PUT(regt, regh, ED_P0_ISR, 0xff);

        /* Program command register for page 1. */
        NIC_BARRIER(regt, regh);
        NIC_PUT(regt, regh, ED_P0_CR,
            sc->cr_proto | ED_CR_PAGE_1 | ED_CR_STP);
        NIC_BARRIER(regt, regh);

        /* Copy out our station address. */
        for (i = 0; i < ETHER_ADDR_LEN; ++i)
                NIC_PUT(regt, regh, ED_P1_PAR0 + i,
                    sc->sc_arpcom.ac_enaddr[i]);

        /* Set multicast filter on chip. */
        dp8390_getmcaf(&sc->sc_arpcom, mcaf);
        for (i = 0; i < 8; i++)
                NIC_PUT(regt, regh, ED_P1_MAR0 + i, mcaf[i]);

        /*
         * Set current page pointer to one page after the boundary pointer, as
         * recommended in the National manual.
         */
        sc->next_packet = sc->rec_page_start + 1;
        NIC_PUT(regt, regh, ED_P1_CURR, sc->next_packet);

        /* Program command register for page 0. */
        NIC_BARRIER(regt, regh);
        NIC_PUT(regt, regh, ED_P1_CR,
            sc->cr_proto | ED_CR_PAGE_0 | ED_CR_STP);
        NIC_BARRIER(regt, regh);

        /* Accept broadcast and multicast packets by default. */
        i = ED_RCR_AB | ED_RCR_AM | sc->rcr_proto;
        if (ifp->if_flags & IFF_PROMISC) {
                /*
                 * Set promiscuous mode.  Multicast filter was set earlier so
                 * that we should receive all multicast packets.
                 */
                i |= ED_RCR_PRO | ED_RCR_AR | ED_RCR_SEP;
        }
        NIC_PUT(regt, regh, ED_P0_RCR, i);

        /* Take interface out of loopback. */
        NIC_PUT(regt, regh, ED_P0_TCR, 0);

        /* Do any card-specific initialization, if applicable. */
        if (sc->init_card)
                (*sc->init_card)(sc);

        /* Fire up the interface. */
        NIC_BARRIER(regt, regh);
        NIC_PUT(regt, regh, ED_P0_CR,
            sc->cr_proto | ED_CR_PAGE_0 | ED_CR_STA);

        /* Set 'running' flag, and clear output active flag. */
        ifp->if_flags |= IFF_RUNNING;
        ifq_clr_oactive(&ifp->if_snd);

        /* ...and attempt to start output. */
        dp8390_start(ifp);
}

/*
 * This routine actually starts the transmission on the interface.
 */
static __inline__ void
dp8390_xmit(struct dp8390_softc *sc)
{
        bus_space_tag_t regt = sc->sc_regt;
        bus_space_handle_t regh = sc->sc_regh;
        struct ifnet *ifp = &sc->sc_arpcom.ac_if;
        u_short len;

#ifdef DIAGNOSTIC
        if ((sc->txb_next_tx + sc->txb_inuse) % sc->txb_cnt != sc->txb_new)
                panic("dp8390_xmit: desync, next_tx=%d inuse=%d cnt=%d new=%d",
                    sc->txb_next_tx, sc->txb_inuse, sc->txb_cnt, sc->txb_new);

        if (sc->txb_inuse == 0)
                panic("dp8390_xmit: no packets to xmit");
#endif

        len = sc->txb_len[sc->txb_next_tx];

        /* Set NIC for page 0 register access. */
        NIC_BARRIER(regt, regh);
        NIC_PUT(regt, regh, ED_P0_CR,
            sc->cr_proto | ED_CR_PAGE_0 | ED_CR_STA);
        NIC_BARRIER(regt, regh);

        /* Set TX buffer start page. */
        NIC_PUT(regt, regh, ED_P0_TPSR, sc->tx_page_start +
            sc->txb_next_tx * ED_TXBUF_SIZE);

        /* Set TX length. */
        NIC_PUT(regt, regh, ED_P0_TBCR0, len);
        NIC_PUT(regt, regh, ED_P0_TBCR1, len >> 8);

        /* Set page 0, remote DMA complete, transmit packet, and *start*. */
        NIC_BARRIER(regt, regh);
        NIC_PUT(regt, regh, ED_P0_CR,
            sc->cr_proto | ED_CR_PAGE_0 | ED_CR_TXP | ED_CR_STA);

        /* Point to next transmit buffer slot and wrap if necessary. */
        if (++sc->txb_next_tx == sc->txb_cnt)
                sc->txb_next_tx = 0;

        /* Set a timer just in case we never hear from the board again. */
        ifp->if_timer = 2;
}

/*
 * Start output on interface.
 * We make two assumptions here:
 *  1) that the current priority is set to splnet _before_ this code
 *     is called *and* is returned to the appropriate priority after
 *     return
 *  2) that the IFF_OACTIVE flag is checked before this code is called
 *     (i.e. that the output part of the interface is idle)
 */
void
dp8390_start(struct ifnet *ifp)
{
        struct dp8390_softc *sc = ifp->if_softc;
        struct mbuf *m0;
        int buffer;
        int len;

        if (!(ifp->if_flags & IFF_RUNNING) || ifq_is_oactive(&ifp->if_snd))
                return;

outloop:
        /* See if there is room to put another packet in the buffer. */
        if (sc->txb_inuse == sc->txb_cnt) {
                /* No room.  Indicate this to the outside world and exit. */
                ifq_set_oactive(&ifp->if_snd);
                return;
        }
        m0 = ifq_dequeue(&ifp->if_snd);
        if (m0 == NULL)
                return;

        /* We need to use m->m_pkthdr.len, so require the header */
        if ((m0->m_flags & M_PKTHDR) == 0)
                panic("dp8390_start: no header mbuf");

#if NBPFILTER > 0
        /* Tap off here if there is a BPF listener. */
        if (ifp->if_bpf)
                bpf_mtap(ifp->if_bpf, m0, BPF_DIRECTION_OUT);
#endif

        /* txb_new points to next open buffer slot. */
        buffer = sc->mem_start +
            ((sc->txb_new * ED_TXBUF_SIZE) << ED_PAGE_SHIFT);

        if (sc->write_mbuf)
                len = (*sc->write_mbuf)(sc, m0, buffer);
        else
                len = dp8390_write_mbuf(sc, m0, buffer);

        m_freem(m0);
        sc->txb_len[sc->txb_new] = max(len, ETHER_MIN_LEN - ETHER_CRC_LEN);

        /* Point to next buffer slot and wrap if necessary. */
        if (++sc->txb_new == sc->txb_cnt)
                sc->txb_new = 0;

        /* Start the first packet transmitting. */
        if (sc->txb_inuse++ == 0)
                dp8390_xmit(sc);

        /* Loop back to the top to possibly buffer more packets. */
        goto outloop;
}

/*
 * Ethernet interface receiver interrupt.
 */
void
dp8390_rint(struct dp8390_softc *sc)
{
        bus_space_tag_t regt = sc->sc_regt;
        bus_space_handle_t regh = sc->sc_regh;
        struct ifnet *ifp = &sc->sc_arpcom.ac_if;
        struct mbuf_list ml = MBUF_LIST_INITIALIZER();
        struct dp8390_ring packet_hdr;
        struct mbuf *m;
        int packet_ptr;
        u_short len;
        u_char boundary, current;
        u_char nlen;

loop:
        /* Set NIC to page 1 registers to get 'current' pointer. */
        NIC_BARRIER(regt, regh);
        NIC_PUT(regt, regh, ED_P0_CR,
            sc->cr_proto | ED_CR_PAGE_1 | ED_CR_STA);
        NIC_BARRIER(regt, regh);

        /*
         * 'sc->next_packet' is the logical beginning of the ring-buffer - i.e.
         * it points to where new data has been buffered.  The 'CURR' (current)
         * register points to the logical end of the ring-buffer - i.e. it
         * points to where additional new data will be added.  We loop here
         * until the logical beginning equals the logical end (or in other
         * words, until the ring-buffer is empty).
         */
        current = NIC_GET(regt, regh, ED_P1_CURR);
        if (sc->next_packet == current)
                goto exit;

        /* Set NIC to page 0 registers to update boundary register. */
        NIC_BARRIER(regt, regh);
        NIC_PUT(regt, regh, ED_P1_CR,
            sc->cr_proto | ED_CR_PAGE_0 | ED_CR_STA);
        NIC_BARRIER(regt, regh);

        do {
                /* Get pointer to this buffer's header structure. */
                packet_ptr = sc->mem_ring +
                    ((sc->next_packet - sc->rec_page_start) << ED_PAGE_SHIFT);

                if (sc->read_hdr)
                        (*sc->read_hdr)(sc, packet_ptr, &packet_hdr);
                else
                        dp8390_read_hdr(sc, packet_ptr, &packet_hdr);
                len = packet_hdr.count;

                /*
                 * Try do deal with old, buggy chips that sometimes duplicate
                 * the low byte of the length into the high byte.  We do this
                 * by simply ignoring the high byte of the length and always
                 * recalculating it.
                 *
                 * NOTE: sc->next_packet is pointing at the current packet.
                 */
                if (packet_hdr.next_packet >= sc->next_packet)
                        nlen = (packet_hdr.next_packet - sc->next_packet);
                else
                        nlen = ((packet_hdr.next_packet - sc->rec_page_start) +
                            (sc->rec_page_stop - sc->next_packet));
                --nlen;
                if ((len & ED_PAGE_MASK) + sizeof(packet_hdr) > ED_PAGE_SIZE)
                        --nlen;
                len = (len & ED_PAGE_MASK) | (nlen << ED_PAGE_SHIFT);
#ifdef DIAGNOSTIC
                if (len != packet_hdr.count) {
                        printf("%s: length does not match "
                            "next packet pointer\n", sc->sc_dev.dv_xname);
                        printf("%s: len %04x nlen %04x start %02x "
                            "first %02x curr %02x next %02x stop %02x\n",
                            sc->sc_dev.dv_xname, packet_hdr.count, len,
                            sc->rec_page_start, sc->next_packet, current,
                            packet_hdr.next_packet, sc->rec_page_stop);
                }
#endif

                /*
                 * Be fairly liberal about what we allow as a "reasonable"
                 * length so that a [crufty] packet will make it to BPF (and
                 * can thus be analyzed).  Note that all that is really
                 * important is that we have a length that will fit into one
                 * mbuf cluster or less; the upper layer protocols can then
                 * figure out the length from their own length field(s).
                 */
                if (len <= MCLBYTES &&
                    packet_hdr.next_packet >= sc->rec_page_start &&
                    packet_hdr.next_packet < sc->rec_page_stop) {
                        /* Go get packet. */
                        m = dp8390_get(sc,
                            packet_ptr + sizeof(struct dp8390_ring),
                            len - sizeof(struct dp8390_ring));
                        if (m == NULL) {
                                ifp->if_ierrors++;
                                goto exit;
                        }
                        ml_enqueue(&ml, m);
                } else {
                        /* Really BAD.  The ring pointers are corrupted. */
                        log(LOG_ERR, "%s: NIC memory corrupt - "
                            "invalid packet length %d\n",
                            sc->sc_dev.dv_xname, len);
                        ifp->if_ierrors++;
                        dp8390_reset(sc);
                        goto exit;
                }

                /* Update next packet pointer. */
                sc->next_packet = packet_hdr.next_packet;

                /*
                 * Update NIC boundary pointer - being careful to keep it one
                 * buffer behind (as recommended by NS databook).
                 */
                boundary = sc->next_packet - 1;
                if (boundary < sc->rec_page_start)
                        boundary = sc->rec_page_stop - 1;
                NIC_PUT(regt, regh, ED_P0_BNRY, boundary);
        } while (sc->next_packet != current);

        goto loop;

exit:
        if_input(ifp, &ml);
}

/* Ethernet interface interrupt processor. */
int
dp8390_intr(void *arg)
{
        struct dp8390_softc *sc = (struct dp8390_softc *)arg;
        bus_space_tag_t regt = sc->sc_regt;
        bus_space_handle_t regh = sc->sc_regh;
        struct ifnet *ifp = &sc->sc_arpcom.ac_if;
        u_char isr;

        if (sc->sc_enabled == 0)
                return (0);

        /* Set NIC to page 0 registers. */
        NIC_BARRIER(regt, regh);
        NIC_PUT(regt, regh, ED_P0_CR,
            sc->cr_proto | ED_CR_PAGE_0 | ED_CR_STA);
        NIC_BARRIER(regt, regh);

        isr = NIC_GET(regt, regh, ED_P0_ISR);
        if (!isr)
                return (0);

        /* Loop until there are no more new interrupts. */
        for (;;) {
                /*
                 * Reset all the bits that we are 'acknowledging' by writing a
                 * '1' to each bit position that was set.
                 * (Writing a '1' *clears* the bit.)
                 */
                NIC_PUT(regt, regh, ED_P0_ISR, isr);

                /* Work around for AX88190 bug */
                if ((sc->sc_flags & DP8390_DO_AX88190_WORKAROUND) != 0)
                        while ((NIC_GET(regt, regh, ED_P0_ISR) & isr) != 0) {
                                NIC_PUT(regt, regh, ED_P0_ISR, 0);
                                NIC_PUT(regt, regh, ED_P0_ISR, isr);
                        }

                /*
                 * Handle transmitter interrupts.  Handle these first because
                 * the receiver will reset the board under some conditions.
                 *
                 * If the chip was reset while a packet was transmitting, it
                 * may still deliver a TX interrupt.  In this case, just ignore
                 * the interrupt.
                 */
                if (isr & (ED_ISR_PTX | ED_ISR_TXE) &&
                    sc->txb_inuse != 0) {
                        u_char collisions =
                            NIC_GET(regt, regh, ED_P0_NCR) & 0x0f;

                        /*
                         * Check for transmit error.  If a TX completed with an
                         * error, we end up throwing the packet away.  Really
                         * the only error that is possible is excessive
                         * collisions, and in this case it is best to allow the
                         * automatic mechanisms of TCP to backoff the flow.  Of
                         * course, with UDP we're screwed, but this is expected
                         * when a network is heavily loaded.
                         */
                        if (isr & ED_ISR_TXE) {
                                /*
                                 * Excessive collisions (16).
                                 */
                                if ((NIC_GET(regt, regh, ED_P0_TSR)
                                    & ED_TSR_ABT) && (collisions == 0)) {
                                        /*
                                         * When collisions total 16, the P0_NCR
                                         * will indicate 0, and the TSR_ABT is
                                         * set.
                                         */
                                        collisions = 16;
                                }

                                /* Update output errors counter. */
                                ++ifp->if_oerrors;
                        } else {
                                /*
                                 * Throw away the non-error status bits.
                                 *
                                 * XXX
                                 * It may be useful to detect loss of carrier
                                 * and late collisions here.
                                 */
                                (void)NIC_GET(regt, regh, ED_P0_TSR);
                        }

                        /* Clear watchdog timer. */
                        ifp->if_timer = 0;
                        ifq_clr_oactive(&ifp->if_snd);

                        /*
                         * Add in total number of collisions on last
                         * transmission.
                         */
                        ifp->if_collisions += collisions;

                        /*
                         * Decrement buffer in-use count if not zero (can only
                         * be zero if a transmitter interrupt occurred while not
                         * actually transmitting).
                         * If data is ready to transmit, start it transmitting,
                         * otherwise defer until after handling receiver.
                         */
                        if (--sc->txb_inuse != 0)
                                dp8390_xmit(sc);
                }

                /* Handle receiver interrupts. */
                if (isr & (ED_ISR_PRX | ED_ISR_RXE | ED_ISR_OVW)) {
                        /*
                         * Overwrite warning.  In order to make sure that a
                         * lockup of the local DMA hasn't occurred, we reset
                         * and re-init the NIC.  The NSC manual suggests only a
                         * partial reset/re-init is necessary - but some chips
                         * seem to want more.  The DMA lockup has been seen
                         * only with early rev chips - Methinks this bug was
                         * fixed in later revs.  -DG
                         */
                        if (isr & ED_ISR_OVW) {
                                ++ifp->if_ierrors;
#ifdef DEBUG
                                log(LOG_WARNING, "%s: warning - receiver "
                                    "ring buffer overrun\n",
                                    sc->sc_dev.dv_xname);
#endif
                                /* Stop/reset/re-init NIC. */
                                dp8390_reset(sc);
                        } else {
                                /*
                                 * Receiver Error.  One or more of: CRC error,
                                 * frame alignment error FIFO overrun, or
                                 * missed packet.
                                 */
                                if (isr & ED_ISR_RXE) {
                                        ++ifp->if_ierrors;
#ifdef DEBUG
                                        if (dp8390_debug) {
                                                printf("%s: receive error %x\n",
                                                    sc->sc_dev.dv_xname,
                                                    NIC_GET(regt, regh,
                                                        ED_P0_RSR));
                                        }
#endif
                                }

                                /*
                                 * Go get the packet(s)
                                 * XXX - Doing this on an error is dubious
                                 * because there shouldn't be any data to get
                                 * (we've configured the interface to not
                                 * accept packets with errors).
                                 */
                                if (sc->recv_int)
                                        (*sc->recv_int)(sc);
                                else
                                        dp8390_rint(sc);
                        }
                }

                /*
                 * If it looks like the transmitter can take more data, attempt
                 * to start output on the interface.  This is done after
                 * handling the receiver to give the receiver priority.
                 */
                dp8390_start(ifp);

                /*
                 * Return NIC CR to standard state: page 0, remote DMA
                 * complete, start (toggling the TXP bit off, even if was just
                 * set in the transmit routine, is *okay* - it is 'edge'
                 * triggered from low to high).
                 */
                NIC_BARRIER(regt, regh);
                NIC_PUT(regt, regh, ED_P0_CR,
                    sc->cr_proto | ED_CR_PAGE_0 | ED_CR_STA);
                NIC_BARRIER(regt, regh);

                /*
                 * If the Network Talley Counters overflow, read them to reset
                 * them.  It appears that old 8390's won't clear the ISR flag
                 * otherwise - resulting in an infinite loop.
                 */
                if (isr & ED_ISR_CNT) {
                        (void)NIC_GET(regt, regh, ED_P0_CNTR0);
                        (void)NIC_GET(regt, regh, ED_P0_CNTR1);
                        (void)NIC_GET(regt, regh, ED_P0_CNTR2);
                }

                isr = NIC_GET(regt, regh, ED_P0_ISR);
                if (!isr)
                        return (1);
        }
}

int
dp8390_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
{
        struct dp8390_softc *sc = ifp->if_softc;
        struct ifreq *ifr = (struct ifreq *) data;
        int s, error = 0;

        s = splnet();

        switch (cmd) {
        case SIOCSIFADDR:
                if ((error = dp8390_enable(sc)) != 0)
                        break;
                ifp->if_flags |= IFF_UP;
                if (!(ifp->if_flags & IFF_RUNNING))
                        dp8390_init(sc);
                break;

        case SIOCSIFFLAGS:
                if (ifp->if_flags & IFF_UP) {
                        if (ifp->if_flags & IFF_RUNNING)
                                error = ENETRESET;
                        else {
                                if ((error = dp8390_enable(sc)) != 0)
                                        break;
                                dp8390_init(sc);
                        }
                } else {
                        if (ifp->if_flags & IFF_RUNNING) {
                                dp8390_stop(sc);
                                ifp->if_flags &= ~IFF_RUNNING;
                                dp8390_disable(sc);
                        }
                }
                break;

        case SIOCGIFMEDIA:
        case SIOCSIFMEDIA:
                error = ifmedia_ioctl(ifp, ifr, &sc->sc_media, cmd);
                break;

        default:
                error = ether_ioctl(ifp, &sc->sc_arpcom, cmd, data);
        }

        if (error == ENETRESET) {
                if (ifp->if_flags & IFF_RUNNING) {
                        dp8390_stop(sc);
                        dp8390_init(sc);
                }
                error = 0;
        }

        splx(s);
        return (error);
}

/*
 * Supporting routines.
 */

/*
 * Compute the multicast address filter from the list of multicast addresses we
 * need to listen to.
 */
void
dp8390_getmcaf(struct arpcom *ac, u_int8_t *af)
{
        struct ifnet *ifp = &ac->ac_if;
        struct ether_multi *enm;
        u_int32_t crc;
        int i;
        struct ether_multistep step;

        /*
         * Set up multicast address filter by passing all multicast addresses
         * through a crc generator, and then using the high order 6 bits as an
         * index into the 64 bit logical address filter.  The high order bit
         * selects the word, while the rest of the bits select the bit within
         * the word.
         */

        if (ifp->if_flags & IFF_PROMISC || ac->ac_multirangecnt > 0) {
                ifp->if_flags |= IFF_ALLMULTI;
                for (i = 0; i < 8; i++)
                        af[i] = 0xff;
                return;
        }
        for (i = 0; i < 8; i++)
                af[i] = 0;
        ETHER_FIRST_MULTI(step, ac, enm);
        while (enm != NULL) {
                /* Just want the 6 most significant bits. */
                crc = ether_crc32_be(enm->enm_addrlo, ETHER_ADDR_LEN) >> 26;

                /* Turn on the corresponding bit in the filter. */
                af[crc >> 3] |= 1 << (crc & 0x7);

                ETHER_NEXT_MULTI(step, enm);
        }
        ifp->if_flags &= ~IFF_ALLMULTI;
}

/*
 * Copy data from receive buffer to a new mbuf chain allocating mbufs
 * as needed.  Return pointer to first mbuf in chain.
 * sc = dp8390 info (softc)
 * src = pointer in dp8390 ring buffer
 * total_len = amount of data to copy
 */
struct mbuf *
dp8390_get(struct dp8390_softc *sc, int src, u_short total_len)
{
        struct mbuf *m, *m0, *newm;
        u_short len;

        MGETHDR(m0, M_DONTWAIT, MT_DATA);
        if (m0 == NULL)
                return (0);
        m0->m_pkthdr.len = total_len;
        len = MHLEN;
        m = m0;

        while (total_len > 0) {
                if (total_len >= MINCLSIZE) {
                        MCLGET(m, M_DONTWAIT);
                        if (!(m->m_flags & M_EXT))
                                goto bad;
                        len = MCLBYTES;
                }

                /*
                 * Make sure the data after the Ethernet header is aligned.
                 */
                if (m == m0) {
                        caddr_t newdata = (caddr_t)
                            ALIGN(m->m_data + sizeof(struct ether_header)) -
                            sizeof(struct ether_header);
                        len -= newdata - m->m_data;
                        m->m_data = newdata;
                }

                m->m_len = len = min(total_len, len);
                if (sc->ring_copy)
                        src = (*sc->ring_copy)(sc, src, mtod(m, caddr_t), len);
                else
                        src = dp8390_ring_copy(sc, src, mtod(m, caddr_t), len);

                total_len -= len;
                if (total_len > 0) {
                        MGET(newm, M_DONTWAIT, MT_DATA);
                        if (newm == NULL)
                                goto bad;
                        len = MLEN;
                        m = m->m_next = newm;
                }
        }

        return (m0);

bad:
        m_freem(m0);
        return (0);
}


/*
 * Default driver support functions.
 *
 * NOTE: all support functions assume 8-bit shared memory.
 */
/*
 * Zero NIC buffer memory and verify that it is clear.
 */
static int
dp8390_test_mem(struct dp8390_softc *sc)
{
        bus_space_tag_t buft = sc->sc_buft;
        bus_space_handle_t bufh = sc->sc_bufh;
        int i;

        bus_space_set_region_1(buft, bufh, sc->mem_start, 0, sc->mem_size);

        for (i = 0; i < sc->mem_size; ++i) {
                if (bus_space_read_1(buft, bufh, sc->mem_start + i)) {
                        printf(": failed to clear NIC buffer at offset %x - "
                            "check configuration\n", (sc->mem_start + i));
                        return 1;
                }
        }

        return 0;
}

/*
 * Read a packet header from the ring, given the source offset.
 */
static __inline__ void
dp8390_read_hdr(struct dp8390_softc *sc, int src, struct dp8390_ring *hdrp)
{
        bus_space_tag_t buft = sc->sc_buft;
        bus_space_handle_t bufh = sc->sc_bufh;

        /*
         * The byte count includes a 4 byte header that was added by
         * the NIC.
         */
        hdrp->rsr = bus_space_read_1(buft, bufh, src);
        hdrp->next_packet = bus_space_read_1(buft, bufh, src + 1);
        hdrp->count = bus_space_read_1(buft, bufh, src + 2) |
            (bus_space_read_1(buft, bufh, src + 3) << 8);
}

/*
 * Copy `amount' bytes from a packet in the ring buffer to a linear
 * destination buffer, given a source offset and destination address.
 * Takes into account ring-wrap.
 */
static __inline__ int
dp8390_ring_copy(struct dp8390_softc *sc, int src, caddr_t dst, u_short amount)
{
        bus_space_tag_t buft = sc->sc_buft;
        bus_space_handle_t bufh = sc->sc_bufh;
        u_short tmp_amount;

        /* Does copy wrap to lower addr in ring buffer? */
        if (src + amount > sc->mem_end) {
                tmp_amount = sc->mem_end - src;

                /* Copy amount up to end of NIC memory. */
                bus_space_read_region_1(buft, bufh, src, dst, tmp_amount);

                amount -= tmp_amount;
                src = sc->mem_ring;
                dst += tmp_amount;
        }
        bus_space_read_region_1(buft, bufh, src, dst, amount);

        return (src + amount);
}

/*
 * Copy a packet from an mbuf to the transmit buffer on the card.
 *
 * Currently uses an extra buffer/extra memory copy, unless the whole
 * packet fits in one mbuf.
 */
static __inline__ int
dp8390_write_mbuf(struct dp8390_softc *sc, struct mbuf *m, int buf)
{
        bus_space_tag_t buft = sc->sc_buft;
        bus_space_handle_t bufh = sc->sc_bufh;
        u_char *data;
        int len, totlen = 0;

        for (; m ; m = m->m_next) {
                data = mtod(m, u_char *);
                len = m->m_len;
                if (len > 0) {
                        bus_space_write_region_1(buft, bufh, buf, data, len);
                        totlen += len;
                        buf += len;
                }
        }

        return (totlen);
}

/*
 * Enable power on the interface.
 */
int
dp8390_enable(struct dp8390_softc *sc)
{

        if (sc->sc_enabled == 0 && sc->sc_enable != NULL) {
                if ((*sc->sc_enable)(sc) != 0) {
                        printf("%s: device enable failed\n",
                            sc->sc_dev.dv_xname);
                        return (EIO);
                }
        }

        sc->sc_enabled = 1;
        return (0);
}

/*
 * Disable power on the interface.
 */
void
dp8390_disable(struct dp8390_softc *sc)
{
        if (sc->sc_enabled != 0 && sc->sc_disable != NULL) {
                (*sc->sc_disable)(sc);
                sc->sc_enabled = 0;
        }
}

int
dp8390_detach(struct dp8390_softc *sc, int flags)
{
        struct ifnet *ifp = &sc->sc_arpcom.ac_if;

        /* dp8390_disable() checks sc->sc_enabled */
        dp8390_disable(sc);

        if (sc->sc_media_fini != NULL)
                (*sc->sc_media_fini)(sc);

        /* Delete all remaining media. */
        ifmedia_delete_instance(&sc->sc_media, IFM_INST_ANY);

        ether_ifdetach(ifp);
        if_detach(ifp);

        return (0);
}