/*
Ported to U-Boot by Christian Pellegrin <chri@ascensit.com>

Based on sources from the Linux kernel (pcnet_cs.c, 8390.h) and
eCOS(if_dp83902a.c, if_dp83902a.h). Both of these 2 wonderful world
are GPL, so this is, of course, GPL.

==========================================================================

dev/if_dp83902a.c

Ethernet device driver for NS DP83902a ethernet controller

==========================================================================
####ECOSGPLCOPYRIGHTBEGIN####
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Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.

eCos is free software; you can redistribute it and/or modify it under
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eCos is distributed in the hope that it will be useful, but WITHOUT ANY
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FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

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with eCos; if not, write to the Free Software Foundation, Inc.,
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As a special exception, if other files instantiate templates or use macros
or inline functions from this file, or you compile this file and link it
with other works to produce a work based on this file, this file does not
by itself cause the resulting work to be covered by the GNU General Public
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-------------------------------------------
####ECOSGPLCOPYRIGHTEND####
####BSDCOPYRIGHTBEGIN####

-------------------------------------------

Portions of this software may have been derived from OpenBSD or other sources,
and are covered by the appropriate copyright disclaimers included herein.

-------------------------------------------

####BSDCOPYRIGHTEND####
==========================================================================
#####DESCRIPTIONBEGIN####

Author(s):      gthomas
Contributors:   gthomas, jskov, rsandifo
Date:           2001-06-13
Purpose:
Description:

FIXME:          Will fail if pinged with large packets (1520 bytes)
Add promisc config
Add SNMP

####DESCRIPTIONEND####

==========================================================================
*/

#include <common.h>
#include <command.h>
#include <net.h>
#include <malloc.h>

#define mdelay(n)       udelay((n)*1000)
/* forward definition of function used for the uboot interface */
void uboot_push_packet_len(int len);
void uboot_push_tx_done(int key, int val);

/* NE2000 base header file */
#include "ne2000_base.h"

#if defined(CONFIG_DRIVER_AX88796L)
/* AX88796L support */
#include "ax88796.h"
#else
/* Basic NE2000 chip support */
#include "ne2000.h"
#endif

static dp83902a_priv_data_t nic; /* just one instance of the card supported */

static bool
dp83902a_init(void)
{
        dp83902a_priv_data_t *dp = &nic;
        u8* base;
#if defined(NE2000_BASIC_INIT)
        int i;
#endif

        DEBUG_FUNCTION();

        base = dp->base;
        if (!base)
                return false;   /* No device found */

        DEBUG_LINE();

#if defined(NE2000_BASIC_INIT)
        /* AX88796L doesn't need */
        /* Prepare ESA */
        DP_OUT(base, DP_CR, DP_CR_NODMA | DP_CR_PAGE1); /* Select page 1 */
        /* Use the address from the serial EEPROM */
        for (i = 0; i < 6; i++)
                DP_IN(base, DP_P1_PAR0+i, dp->esa[i]);
        DP_OUT(base, DP_CR, DP_CR_NODMA | DP_CR_PAGE0); /* Select page 0 */

        printf("NE2000 - %s ESA: %02x:%02x:%02x:%02x:%02x:%02x\n",
                "eeprom",
                dp->esa[0],
                dp->esa[1],
                dp->esa[2],
                dp->esa[3],
                dp->esa[4],
                dp->esa[5] );

#endif  /* NE2000_BASIC_INIT */
        return true;
}

static void
dp83902a_stop(void)
{
        dp83902a_priv_data_t *dp = &nic;
        u8 *base = dp->base;

        DEBUG_FUNCTION();

        DP_OUT(base, DP_CR, DP_CR_PAGE0 | DP_CR_NODMA | DP_CR_STOP);    /* Brutal */
        DP_OUT(base, DP_ISR, 0xFF);             /* Clear any pending interrupts */
        DP_OUT(base, DP_IMR, 0x00);             /* Disable all interrupts */

        dp->running = false;
}

/*
 * This function is called to "start up" the interface. It may be called
 * multiple times, even when the hardware is already running. It will be
 * called whenever something "hardware oriented" changes and should leave
 * the hardware ready to send/receive packets.
 */
static void
dp83902a_start(u8 * enaddr)
{
        dp83902a_priv_data_t *dp = &nic;
        u8 *base = dp->base;
        int i;

        DEBUG_FUNCTION();

        DP_OUT(base, DP_CR, DP_CR_PAGE0 | DP_CR_NODMA | DP_CR_STOP); /* Brutal */
        DP_OUT(base, DP_DCR, DP_DCR_INIT);
        DP_OUT(base, DP_RBCH, 0);               /* Remote byte count */
        DP_OUT(base, DP_RBCL, 0);
        DP_OUT(base, DP_RCR, DP_RCR_MON);       /* Accept no packets */
        DP_OUT(base, DP_TCR, DP_TCR_LOCAL);     /* Transmitter [virtually] off */
        DP_OUT(base, DP_TPSR, dp->tx_buf1);     /* Transmitter start page */
        dp->tx1 = dp->tx2 = 0;
        dp->tx_next = dp->tx_buf1;
        dp->tx_started = false;
        dp->running = true;
        DP_OUT(base, DP_PSTART, dp->rx_buf_start); /* Receive ring start page */
        DP_OUT(base, DP_BNDRY, dp->rx_buf_end - 1); /* Receive ring boundary */
        DP_OUT(base, DP_PSTOP, dp->rx_buf_end); /* Receive ring end page */
        dp->rx_next = dp->rx_buf_start - 1;
        dp->running = true;
        DP_OUT(base, DP_ISR, 0xFF);             /* Clear any pending interrupts */
        DP_OUT(base, DP_IMR, DP_IMR_All);       /* Enable all interrupts */
        DP_OUT(base, DP_CR, DP_CR_NODMA | DP_CR_PAGE1 | DP_CR_STOP);    /* Select page 1 */
        DP_OUT(base, DP_P1_CURP, dp->rx_buf_start);     /* Current page - next free page for Rx */
        dp->running = true;
        for (i = 0; i < ETHER_ADDR_LEN; i++) {
                /* FIXME */
                /*((vu_short*)( base + ((DP_P1_PAR0 + i) * 2) +
                 * 0x1400)) = enaddr[i];*/
                DP_OUT(base, DP_P1_PAR0+i, enaddr[i]);
        }
        /* Enable and start device */
        DP_OUT(base, DP_CR, DP_CR_PAGE0 | DP_CR_NODMA | DP_CR_START);
        DP_OUT(base, DP_TCR, DP_TCR_NORMAL); /* Normal transmit operations */
        DP_OUT(base, DP_RCR, DP_RCR_AB); /* Accept broadcast, no errors, no multicast */
        dp->running = true;
}

/*
 * This routine is called to start the transmitter. It is split out from the
 * data handling routine so it may be called either when data becomes first
 * available or when an Tx interrupt occurs
 */

static void
dp83902a_start_xmit(int start_page, int len)
{
        dp83902a_priv_data_t *dp = (dp83902a_priv_data_t *) &nic;
        u8 *base = dp->base;

        DEBUG_FUNCTION();

#if DEBUG & 1
        printf("Tx pkt %d len %d\n", start_page, len);
        if (dp->tx_started)
                printf("TX already started?!?\n");
#endif

        DP_OUT(base, DP_ISR, (DP_ISR_TxP | DP_ISR_TxE));
        DP_OUT(base, DP_CR, DP_CR_PAGE0 | DP_CR_NODMA | DP_CR_START);
        DP_OUT(base, DP_TBCL, len & 0xFF);
        DP_OUT(base, DP_TBCH, len >> 8);
        DP_OUT(base, DP_TPSR, start_page);
        DP_OUT(base, DP_CR, DP_CR_NODMA | DP_CR_TXPKT | DP_CR_START);

        dp->tx_started = true;
}

/*
 * This routine is called to send data to the hardware. It is known a-priori
 * that there is free buffer space (dp->tx_next).
 */
static void
dp83902a_send(u8 *data, int total_len, u32 key)
{
        struct dp83902a_priv_data *dp = (struct dp83902a_priv_data *) &nic;
        u8 *base = dp->base;
        int len, start_page, pkt_len, i, isr;
#if DEBUG & 4
        int dx;
#endif

        DEBUG_FUNCTION();

        len = pkt_len = total_len;
        if (pkt_len < IEEE_8023_MIN_FRAME)
                pkt_len = IEEE_8023_MIN_FRAME;

        start_page = dp->tx_next;
        if (dp->tx_next == dp->tx_buf1) {
                dp->tx1 = start_page;
                dp->tx1_len = pkt_len;
                dp->tx1_key = key;
                dp->tx_next = dp->tx_buf2;
        } else {
                dp->tx2 = start_page;
                dp->tx2_len = pkt_len;
                dp->tx2_key = key;
                dp->tx_next = dp->tx_buf1;
        }

#if DEBUG & 5
        printf("TX prep page %d len %d\n", start_page, pkt_len);
#endif

        DP_OUT(base, DP_ISR, DP_ISR_RDC);       /* Clear end of DMA */
        {
                /*
                 * Dummy read. The manual sez something slightly different,
                 * but the code is extended a bit to do what Hitachi's monitor
                 * does (i.e., also read data).
                 */

                u16 tmp;
                int len = 1;

                DP_OUT(base, DP_RSAL, 0x100 - len);
                DP_OUT(base, DP_RSAH, (start_page - 1) & 0xff);
                DP_OUT(base, DP_RBCL, len);
                DP_OUT(base, DP_RBCH, 0);
                DP_OUT(base, DP_CR, DP_CR_PAGE0 | DP_CR_RDMA | DP_CR_START);
                DP_IN_DATA(dp->data, tmp);
        }

#ifdef CYGHWR_NS_DP83902A_PLF_BROKEN_TX_DMA
        /*
         * Stall for a bit before continuing to work around random data
         * corruption problems on some platforms.
         */
        CYGACC_CALL_IF_DELAY_US(1);
#endif

        /* Send data to device buffer(s) */
        DP_OUT(base, DP_RSAL, 0);
        DP_OUT(base, DP_RSAH, start_page);
        DP_OUT(base, DP_RBCL, pkt_len & 0xFF);
        DP_OUT(base, DP_RBCH, pkt_len >> 8);
        DP_OUT(base, DP_CR, DP_CR_WDMA | DP_CR_START);

        /* Put data into buffer */
#if DEBUG & 4
        printf(" sg buf %08lx len %08x\n ", (u32)data, len);
        dx = 0;
#endif
        while (len > 0) {
#if DEBUG & 4
                printf(" %02x", *data);
                if (0 == (++dx % 16)) printf("\n ");
#endif

                DP_OUT_DATA(dp->data, *data++);
                len--;
        }
#if DEBUG & 4
        printf("\n");
#endif
        if (total_len < pkt_len) {
#if DEBUG & 4
                printf("  + %d bytes of padding\n", pkt_len - total_len);
#endif
                /* Padding to 802.3 length was required */
                for (i = total_len; i < pkt_len;) {
                        i++;
                        DP_OUT_DATA(dp->data, 0);
                }
        }

#ifdef CYGHWR_NS_DP83902A_PLF_BROKEN_TX_DMA
        /*
         * After last data write, delay for a bit before accessing the
         * device again, or we may get random data corruption in the last
         * datum (on some platforms).
         */
        CYGACC_CALL_IF_DELAY_US(1);
#endif

        /* Wait for DMA to complete */
        do {
                DP_IN(base, DP_ISR, isr);
        } while ((isr & DP_ISR_RDC) == 0);

        /* Then disable DMA */
        DP_OUT(base, DP_CR, DP_CR_PAGE0 | DP_CR_NODMA | DP_CR_START);

        /* Start transmit if not already going */
        if (!dp->tx_started) {
                if (start_page == dp->tx1) {
                        dp->tx_int = 1; /* Expecting interrupt from BUF1 */
                } else {
                        dp->tx_int = 2; /* Expecting interrupt from BUF2 */
                }
                dp83902a_start_xmit(start_page, pkt_len);
        }
}

/*
 * This function is called when a packet has been received. It's job is
 * to prepare to unload the packet from the hardware. Once the length of
 * the packet is known, the upper layer of the driver can be told. When
 * the upper layer is ready to unload the packet, the internal function
 * 'dp83902a_recv' will be called to actually fetch it from the hardware.
 */
static void
dp83902a_RxEvent(void)
{
        struct dp83902a_priv_data *dp = (struct dp83902a_priv_data *) &nic;
        u8 *base = dp->base;
        u8 rsr;
        u8 rcv_hdr[4];
        int i, len, pkt, cur;

        DEBUG_FUNCTION();

        DP_IN(base, DP_RSR, rsr);
        while (true) {
                /* Read incoming packet header */
                DP_OUT(base, DP_CR, DP_CR_PAGE1 | DP_CR_NODMA | DP_CR_START);
                DP_IN(base, DP_P1_CURP, cur);
                DP_OUT(base, DP_P1_CR, DP_CR_PAGE0 | DP_CR_NODMA | DP_CR_START);
                DP_IN(base, DP_BNDRY, pkt);

                pkt += 1;
                if (pkt == dp->rx_buf_end)
                        pkt = dp->rx_buf_start;

                if (pkt == cur) {
                        break;
                }
                DP_OUT(base, DP_RBCL, sizeof(rcv_hdr));
                DP_OUT(base, DP_RBCH, 0);
                DP_OUT(base, DP_RSAL, 0);
                DP_OUT(base, DP_RSAH, pkt);
                if (dp->rx_next == pkt) {
                        if (cur == dp->rx_buf_start)
                                DP_OUT(base, DP_BNDRY, dp->rx_buf_end - 1);
                        else
                                DP_OUT(base, DP_BNDRY, cur - 1); /* Update pointer */
                        return;
                }
                dp->rx_next = pkt;
                DP_OUT(base, DP_ISR, DP_ISR_RDC); /* Clear end of DMA */
                DP_OUT(base, DP_CR, DP_CR_RDMA | DP_CR_START);
#ifdef CYGHWR_NS_DP83902A_PLF_BROKEN_RX_DMA
                CYGACC_CALL_IF_DELAY_US(10);
#endif

                /* read header (get data size)*/
                for (i = 0; i < sizeof(rcv_hdr);) {
                        DP_IN_DATA(dp->data, rcv_hdr[i++]);
                }

#if DEBUG & 5
                printf("rx hdr %02x %02x %02x %02x\n",
                        rcv_hdr[0], rcv_hdr[1], rcv_hdr[2], rcv_hdr[3]);
#endif
                len = ((rcv_hdr[3] << 8) | rcv_hdr[2]) - sizeof(rcv_hdr);

                /* data read */
                uboot_push_packet_len(len);

                if (rcv_hdr[1] == dp->rx_buf_start)
                        DP_OUT(base, DP_BNDRY, dp->rx_buf_end - 1);
                else
                        DP_OUT(base, DP_BNDRY, rcv_hdr[1] - 1); /* Update pointer */
        }
}

/*
 * This function is called as a result of the "eth_drv_recv()" call above.
 * It's job is to actually fetch data for a packet from the hardware once
 * memory buffers have been allocated for the packet. Note that the buffers
 * may come in pieces, using a scatter-gather list. This allows for more
 * efficient processing in the upper layers of the stack.
 */
static void
dp83902a_recv(u8 *data, int len)
{
        struct dp83902a_priv_data *dp = (struct dp83902a_priv_data *) &nic;
        u8 *base = dp->base;
        int i, mlen;
        u8 saved_char = 0;
        bool saved;
#if DEBUG & 4
        int dx;
#endif

        DEBUG_FUNCTION();

#if DEBUG & 5
        printf("Rx packet %d length %d\n", dp->rx_next, len);
#endif

        /* Read incoming packet data */
        DP_OUT(base, DP_CR, DP_CR_PAGE0 | DP_CR_NODMA | DP_CR_START);
        DP_OUT(base, DP_RBCL, len & 0xFF);
        DP_OUT(base, DP_RBCH, len >> 8);
        DP_OUT(base, DP_RSAL, 4);               /* Past header */
        DP_OUT(base, DP_RSAH, dp->rx_next);
        DP_OUT(base, DP_ISR, DP_ISR_RDC); /* Clear end of DMA */
        DP_OUT(base, DP_CR, DP_CR_RDMA | DP_CR_START);
#ifdef CYGHWR_NS_DP83902A_PLF_BROKEN_RX_DMA
        CYGACC_CALL_IF_DELAY_US(10);
#endif

        saved = false;
        for (i = 0; i < 1; i++) {
                if (data) {
                        mlen = len;
#if DEBUG & 4
                        printf(" sg buf %08lx len %08x \n", (u32) data, mlen);
                        dx = 0;
#endif
                        while (0 < mlen) {
                                /* Saved byte from previous loop? */
                                if (saved) {
                                        *data++ = saved_char;
                                        mlen--;
                                        saved = false;
                                        continue;
                                }

                                {
                                        u8 tmp;
                                        DP_IN_DATA(dp->data, tmp);
#if DEBUG & 4
                                        printf(" %02x", tmp);
                                        if (0 == (++dx % 16)) printf("\n ");
#endif
                                        *data++ = tmp;;
                                        mlen--;
                                }
                        }
#if DEBUG & 4
                        printf("\n");
#endif
                }
        }
}

static void
dp83902a_TxEvent(void)
{
        struct dp83902a_priv_data *dp = (struct dp83902a_priv_data *) &nic;
        u8 *base = dp->base;
        u8 tsr;
        u32 key;

        DEBUG_FUNCTION();

        DP_IN(base, DP_TSR, tsr);
        if (dp->tx_int == 1) {
                key = dp->tx1_key;
                dp->tx1 = 0;
        } else {
                key = dp->tx2_key;
                dp->tx2 = 0;
        }
        /* Start next packet if one is ready */
        dp->tx_started = false;
        if (dp->tx1) {
                dp83902a_start_xmit(dp->tx1, dp->tx1_len);
                dp->tx_int = 1;
        } else if (dp->tx2) {
                dp83902a_start_xmit(dp->tx2, dp->tx2_len);
                dp->tx_int = 2;
        } else {
                dp->tx_int = 0;
        }
        /* Tell higher level we sent this packet */
        uboot_push_tx_done(key, 0);
}

/*
 * Read the tally counters to clear them. Called in response to a CNT
 * interrupt.
 */
static void
dp83902a_ClearCounters(void)
{
        struct dp83902a_priv_data *dp = (struct dp83902a_priv_data *) &nic;
        u8 *base = dp->base;
        u8 cnt1, cnt2, cnt3;

        DP_IN(base, DP_FER, cnt1);
        DP_IN(base, DP_CER, cnt2);
        DP_IN(base, DP_MISSED, cnt3);
        DP_OUT(base, DP_ISR, DP_ISR_CNT);
}

/*
 * Deal with an overflow condition. This code follows the procedure set
 * out in section 7.0 of the datasheet.
 */
static void
dp83902a_Overflow(void)
{
        struct dp83902a_priv_data *dp = (struct dp83902a_priv_data *)&nic;
        u8 *base = dp->base;
        u8 isr;

        /* Issue a stop command and wait 1.6ms for it to complete. */
        DP_OUT(base, DP_CR, DP_CR_STOP | DP_CR_NODMA);
        CYGACC_CALL_IF_DELAY_US(1600);

        /* Clear the remote byte counter registers. */
        DP_OUT(base, DP_RBCL, 0);
        DP_OUT(base, DP_RBCH, 0);

        /* Enter loopback mode while we clear the buffer. */
        DP_OUT(base, DP_TCR, DP_TCR_LOCAL);
        DP_OUT(base, DP_CR, DP_CR_START | DP_CR_NODMA);

        /*
         * Read in as many packets as we can and acknowledge any and receive
         * interrupts. Since the buffer has overflowed, a receive event of
         * some kind will have occured.
         */
        dp83902a_RxEvent();
        DP_OUT(base, DP_ISR, DP_ISR_RxP|DP_ISR_RxE);

        /* Clear the overflow condition and leave loopback mode. */
        DP_OUT(base, DP_ISR, DP_ISR_OFLW);
        DP_OUT(base, DP_TCR, DP_TCR_NORMAL);

        /*
         * If a transmit command was issued, but no transmit event has occured,
         * restart it here.
         */
        DP_IN(base, DP_ISR, isr);
        if (dp->tx_started && !(isr & (DP_ISR_TxP|DP_ISR_TxE))) {
                DP_OUT(base, DP_CR, DP_CR_NODMA | DP_CR_TXPKT | DP_CR_START);
        }
}

static void
dp83902a_poll(void)
{
        struct dp83902a_priv_data *dp = (struct dp83902a_priv_data *) &nic;
        u8 *base = dp->base;
        u8 isr;

        DP_OUT(base, DP_CR, DP_CR_NODMA | DP_CR_PAGE0 | DP_CR_START);
        DP_IN(base, DP_ISR, isr);
        while (0 != isr) {
                /*
                 * The CNT interrupt triggers when the MSB of one of the error
                 * counters is set. We don't much care about these counters, but
                 * we should read their values to reset them.
                 */
                if (isr & DP_ISR_CNT) {
                        dp83902a_ClearCounters();
                }
                /*
                 * Check for overflow. It's a special case, since there's a
                 * particular procedure that must be followed to get back into
                 * a running state.a
                 */
                if (isr & DP_ISR_OFLW) {
                        dp83902a_Overflow();
                } else {
                        /*
                         * Other kinds of interrupts can be acknowledged simply by
                         * clearing the relevant bits of the ISR. Do that now, then
                         * handle the interrupts we care about.
                         */
                        DP_OUT(base, DP_ISR, isr);      /* Clear set bits */
                        if (!dp->running) break;        /* Is this necessary? */
                        /*
                         * Check for tx_started on TX event since these may happen
                         * spuriously it seems.
                         */
                        if (isr & (DP_ISR_TxP|DP_ISR_TxE) && dp->tx_started) {
                                dp83902a_TxEvent();
                        }
                        if (isr & (DP_ISR_RxP|DP_ISR_RxE)) {
                                dp83902a_RxEvent();
                        }
                }
                DP_IN(base, DP_ISR, isr);
        }
}


/* U-boot specific routines */
static u8 *pbuf = NULL;

static int pkey = -1;
static int initialized = 0;

void uboot_push_packet_len(int len) {
        PRINTK("pushed len = %d\n", len);
        if (len >= 2000) {
                printf("NE2000: packet too big\n");
                return;
        }
        dp83902a_recv(&pbuf[0], len);

        /*Just pass it to the upper layer*/
        NetReceive(&pbuf[0], len);
}

void uboot_push_tx_done(int key, int val) {
        PRINTK("pushed key = %d\n", key);
        pkey = key;
}

int eth_init(bd_t *bd) {
        int r;
        u8 dev_addr[6];
        char ethaddr[20];

        PRINTK("### eth_init\n");

        if (!pbuf) {
                pbuf = malloc(2000);
                if (!pbuf) {
                        printf("Cannot allocate rx buffer\n");
                        return -1;
                }
        }

#ifdef CONFIG_DRIVER_NE2000_CCR
        {
                vu_char *p = (vu_char *) CONFIG_DRIVER_NE2000_CCR;

                PRINTK("CCR before is %x\n", *p);
                *p = CONFIG_DRIVER_NE2000_VAL;
                PRINTK("CCR after is %x\n", *p);
        }
#endif

        nic.base = (u8 *) CONFIG_DRIVER_NE2000_BASE;

        r = get_prom(dev_addr, nic.base);
        if (!r)
                return -1;

        sprintf (ethaddr, "%02X:%02X:%02X:%02X:%02X:%02X",
                 dev_addr[0], dev_addr[1],
                 dev_addr[2], dev_addr[3],
                 dev_addr[4], dev_addr[5]) ;
        PRINTK("Set environment from HW MAC addr = \"%s\"\n", ethaddr);
        setenv ("ethaddr", ethaddr);

        nic.data = nic.base + DP_DATA;
        nic.tx_buf1 = START_PG;
        nic.tx_buf2 = START_PG2;
        nic.rx_buf_start = RX_START;
        nic.rx_buf_end = RX_END;

        if (dp83902a_init() == false)
                return -1;

        dp83902a_start(dev_addr);
        initialized = 1;

        return 0;
}

void eth_halt() {

        PRINTK("### eth_halt\n");
        if(initialized)
                dp83902a_stop();
        initialized = 0;
}

int eth_rx() {
        dp83902a_poll();
        return 1;
}

int eth_send(volatile void *packet, int length) {
        int tmo;

        PRINTK("### eth_send\n");

        pkey = -1;

        dp83902a_send((u8 *) packet, length, 666);
        tmo = get_timer (0) + TOUT * CONFIG_SYS_HZ;
        while(1) {
                dp83902a_poll();
                if (pkey != -1) {
                        PRINTK("Packet sucesfully sent\n");
                        return 0;
                }
                if (get_timer (0) >= tmo) {
                        printf("transmission error (timoeut)\n");
                        return 0;
                }

        }
        return 0;
}