Archipelago » qemu

/**

 * QEMU RTL8139 emulation

 * 

 * Copyright (c) 2006 Igor Kovalenko

 * 

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 * Modifications:

 *  2006-Jan-28  Mark Malakanov :   TSAD and CSCR implementation (for Windows driver)

 *                 

 */

#include "vl.h"

/* debug RTL8139 card */

//#define DEBUG_RTL8139 1

/* debug RTL8139 card C+ mode only */

//#define DEBUG_RTL8139CP 1

/* RTL8139 provides frame CRC with received packet, this feature seems to be

   ignored by most drivers, disabled by default */

//#define RTL8139_CALCULATE_RXCRC 1

#if defined(RTL8139_CALCULATE_RXCRC)

/* For crc32 */

#include <zlib.h>

#endif

#define SET_MASKED(input, mask, curr) \

    ( ( (input) & ~(mask) ) | ( (curr) & (mask) ) )

/* arg % size for size which is a power of 2 */

#define MOD2(input, size) \

    ( ( input ) & ( size - 1 )  )

/* Symbolic offsets to registers. */

enum RTL8139_registers {

    MAC0 = 0,        /* Ethernet hardware address. */

    MAR0 = 8,        /* Multicast filter. */

    TxStatus0 = 0x10,    /* Transmit status (Four 32bit registers). */

    TxAddr0 = 0x20,        /* Tx descriptors (also four 32bit). */

    RxBuf = 0x30,

    ChipCmd = 0x37,

    RxBufPtr = 0x38,

    RxBufAddr = 0x3A,

    IntrMask = 0x3C,

    IntrStatus = 0x3E,

    TxConfig = 0x40,

    RxConfig = 0x44,

    Timer = 0x48,        /* A general-purpose counter. */

    RxMissed = 0x4C,    /* 24 bits valid, write clears. */

    Cfg9346 = 0x50,

    Config0 = 0x51,

    Config1 = 0x52,

    FlashReg = 0x54,

    MediaStatus = 0x58,

    Config3 = 0x59,

    Config4 = 0x5A,        /* absent on RTL-8139A */

    HltClk = 0x5B,

    MultiIntr = 0x5C,

    PCIRevisionID = 0x5E,

    TxSummary = 0x60, /* TSAD register. Transmit Status of All Descriptors*/

    BasicModeCtrl = 0x62,

    BasicModeStatus = 0x64,

    NWayAdvert = 0x66,

    NWayLPAR = 0x68,

    NWayExpansion = 0x6A,

    /* Undocumented registers, but required for proper operation. */

    FIFOTMS = 0x70,        /* FIFO Control and test. */

    CSCR = 0x74,        /* Chip Status and Configuration Register. */

    PARA78 = 0x78,

    PARA7c = 0x7c,        /* Magic transceiver parameter register. */

    Config5 = 0xD8,        /* absent on RTL-8139A */

    /* C+ mode */

    TxPoll        = 0xD9,    /* Tell chip to check Tx descriptors for work */

    RxMaxSize    = 0xDA, /* Max size of an Rx packet (8169 only) */

    CpCmd        = 0xE0, /* C+ Command register (C+ mode only) */

    IntrMitigate    = 0xE2,    /* rx/tx interrupt mitigation control */

    RxRingAddrLO    = 0xE4, /* 64-bit start addr of Rx ring */

    RxRingAddrHI    = 0xE8, /* 64-bit start addr of Rx ring */

    TxThresh    = 0xEC, /* Early Tx threshold */

};

enum ClearBitMasks {

    MultiIntrClear = 0xF000,

    ChipCmdClear = 0xE2,

    Config1Clear = (1<<7)|(1<<6)|(1<<3)|(1<<2)|(1<<1),

};

enum ChipCmdBits {

    CmdReset = 0x10,

    CmdRxEnb = 0x08,

    CmdTxEnb = 0x04,

    RxBufEmpty = 0x01,

};

/* C+ mode */

enum CplusCmdBits {

    CPlusRxEnb = 0x0002,

    CPlusTxEnb = 0x0001,

};

/* Interrupt register bits, using my own meaningful names. */

enum IntrStatusBits {

    PCIErr = 0x8000,

    PCSTimeout = 0x4000,

    RxFIFOOver = 0x40,

    RxUnderrun = 0x20,

    RxOverflow = 0x10,

    TxErr = 0x08,

    TxOK = 0x04,

    RxErr = 0x02,

    RxOK = 0x01,

    RxAckBits = RxFIFOOver | RxOverflow | RxOK,

};

enum TxStatusBits {

    TxHostOwns = 0x2000,

    TxUnderrun = 0x4000,

    TxStatOK = 0x8000,

    TxOutOfWindow = 0x20000000,

    TxAborted = 0x40000000,

    TxCarrierLost = 0x80000000,

};

enum RxStatusBits {

    RxMulticast = 0x8000,

    RxPhysical = 0x4000,

    RxBroadcast = 0x2000,

    RxBadSymbol = 0x0020,

    RxRunt = 0x0010,

    RxTooLong = 0x0008,

    RxCRCErr = 0x0004,

    RxBadAlign = 0x0002,

    RxStatusOK = 0x0001,

};

/* Bits in RxConfig. */

enum rx_mode_bits {

    AcceptErr = 0x20,

    AcceptRunt = 0x10,

    AcceptBroadcast = 0x08,

    AcceptMulticast = 0x04,

    AcceptMyPhys = 0x02,

    AcceptAllPhys = 0x01,

};

/* Bits in TxConfig. */

enum tx_config_bits {

        /* Interframe Gap Time. Only TxIFG96 doesn't violate IEEE 802.3 */

        TxIFGShift = 24,

        TxIFG84 = (0 << TxIFGShift),    /* 8.4us / 840ns (10 / 100Mbps) */

        TxIFG88 = (1 << TxIFGShift),    /* 8.8us / 880ns (10 / 100Mbps) */

        TxIFG92 = (2 << TxIFGShift),    /* 9.2us / 920ns (10 / 100Mbps) */

        TxIFG96 = (3 << TxIFGShift),    /* 9.6us / 960ns (10 / 100Mbps) */

    TxLoopBack = (1 << 18) | (1 << 17), /* enable loopback test mode */

    TxCRC = (1 << 16),    /* DISABLE appending CRC to end of Tx packets */

    TxClearAbt = (1 << 0),    /* Clear abort (WO) */

    TxDMAShift = 8,        /* DMA burst value (0-7) is shifted this many bits */

    TxRetryShift = 4,    /* TXRR value (0-15) is shifted this many bits */

    TxVersionMask = 0x7C800000, /* mask out version bits 30-26, 23 */

};

/* Transmit Status of All Descriptors (TSAD) Register */

enum TSAD_bits {

 TSAD_TOK3 = 1<<15, // TOK bit of Descriptor 3

 TSAD_TOK2 = 1<<14, // TOK bit of Descriptor 2

 TSAD_TOK1 = 1<<13, // TOK bit of Descriptor 1

 TSAD_TOK0 = 1<<12, // TOK bit of Descriptor 0

 TSAD_TUN3 = 1<<11, // TUN bit of Descriptor 3

 TSAD_TUN2 = 1<<10, // TUN bit of Descriptor 2

 TSAD_TUN1 = 1<<9, // TUN bit of Descriptor 1

 TSAD_TUN0 = 1<<8, // TUN bit of Descriptor 0

 TSAD_TABT3 = 1<<07, // TABT bit of Descriptor 3

 TSAD_TABT2 = 1<<06, // TABT bit of Descriptor 2

 TSAD_TABT1 = 1<<05, // TABT bit of Descriptor 1

 TSAD_TABT0 = 1<<04, // TABT bit of Descriptor 0

 TSAD_OWN3 = 1<<03, // OWN bit of Descriptor 3

 TSAD_OWN2 = 1<<02, // OWN bit of Descriptor 2

 TSAD_OWN1 = 1<<01, // OWN bit of Descriptor 1

 TSAD_OWN0 = 1<<00, // OWN bit of Descriptor 0

};

/* Bits in Config1 */

enum Config1Bits {

    Cfg1_PM_Enable = 0x01,

    Cfg1_VPD_Enable = 0x02,

    Cfg1_PIO = 0x04,

    Cfg1_MMIO = 0x08,

    LWAKE = 0x10,        /* not on 8139, 8139A */

    Cfg1_Driver_Load = 0x20,

    Cfg1_LED0 = 0x40,

    Cfg1_LED1 = 0x80,

    SLEEP = (1 << 1),    /* only on 8139, 8139A */

    PWRDN = (1 << 0),    /* only on 8139, 8139A */

};

/* Bits in Config3 */

enum Config3Bits {

    Cfg3_FBtBEn    = (1 << 0), /* 1 = Fast Back to Back */

    Cfg3_FuncRegEn = (1 << 1), /* 1 = enable CardBus Function registers */

    Cfg3_CLKRUN_En = (1 << 2), /* 1 = enable CLKRUN */

    Cfg3_CardB_En  = (1 << 3), /* 1 = enable CardBus registers */

    Cfg3_LinkUp    = (1 << 4), /* 1 = wake up on link up */

    Cfg3_Magic     = (1 << 5), /* 1 = wake up on Magic Packet (tm) */

    Cfg3_PARM_En   = (1 << 6), /* 0 = software can set twister parameters */

    Cfg3_GNTSel    = (1 << 7), /* 1 = delay 1 clock from PCI GNT signal */

};

/* Bits in Config4 */

enum Config4Bits {

    LWPTN = (1 << 2),    /* not on 8139, 8139A */

};

/* Bits in Config5 */

enum Config5Bits {

    Cfg5_PME_STS     = (1 << 0), /* 1 = PCI reset resets PME_Status */

    Cfg5_LANWake     = (1 << 1), /* 1 = enable LANWake signal */

    Cfg5_LDPS        = (1 << 2), /* 0 = save power when link is down */

    Cfg5_FIFOAddrPtr = (1 << 3), /* Realtek internal SRAM testing */

    Cfg5_UWF         = (1 << 4), /* 1 = accept unicast wakeup frame */

    Cfg5_MWF         = (1 << 5), /* 1 = accept multicast wakeup frame */

    Cfg5_BWF         = (1 << 6), /* 1 = accept broadcast wakeup frame */

};

enum RxConfigBits {

    /* rx fifo threshold */

    RxCfgFIFOShift = 13,

    RxCfgFIFONone = (7 << RxCfgFIFOShift),

    /* Max DMA burst */

    RxCfgDMAShift = 8,

    RxCfgDMAUnlimited = (7 << RxCfgDMAShift),

    /* rx ring buffer length */

    RxCfgRcv8K = 0,

    RxCfgRcv16K = (1 << 11),

    RxCfgRcv32K = (1 << 12),

    RxCfgRcv64K = (1 << 11) | (1 << 12),

    /* Disable packet wrap at end of Rx buffer. (not possible with 64k) */

    RxNoWrap = (1 << 7),

};

/* Twister tuning parameters from RealTek.

   Completely undocumented, but required to tune bad links on some boards. */

/*

enum CSCRBits {

    CSCR_LinkOKBit = 0x0400,

    CSCR_LinkChangeBit = 0x0800,

    CSCR_LinkStatusBits = 0x0f000,

    CSCR_LinkDownOffCmd = 0x003c0,

    CSCR_LinkDownCmd = 0x0f3c0,

*/

enum CSCRBits {

    CSCR_Testfun = 1<<15, /* 1 = Auto-neg speeds up internal timer, WO, def 0 */ 

    CSCR_LD  = 1<<9,  /* Active low TPI link disable signal. When low, TPI still transmits link pulses and TPI stays in good link state. def 1*/

    CSCR_HEART_BIT = 1<<8,  /* 1 = HEART BEAT enable, 0 = HEART BEAT disable. HEART BEAT function is only valid in 10Mbps mode. def 1*/

    CSCR_JBEN = 1<<7,  /* 1 = enable jabber function. 0 = disable jabber function, def 1*/

    CSCR_F_LINK_100 = 1<<6, /* Used to login force good link in 100Mbps for diagnostic purposes. 1 = DISABLE, 0 = ENABLE. def 1*/ 

    CSCR_F_Connect  = 1<<5,  /* Assertion of this bit forces the disconnect function to be bypassed. def 0*/

    CSCR_Con_status = 1<<3, /* This bit indicates the status of the connection. 1 = valid connected link detected; 0 = disconnected link detected. RO def 0*/

    CSCR_Con_status_En = 1<<2, /* Assertion of this bit configures LED1 pin to indicate connection status. def 0*/

    CSCR_PASS_SCR = 1<<0, /* Bypass Scramble, def 0*/

};

enum Cfg9346Bits {

    Cfg9346_Lock = 0x00,

    Cfg9346_Unlock = 0xC0,

};

typedef enum {

    CH_8139 = 0,

    CH_8139_K,

    CH_8139A,

    CH_8139A_G,

    CH_8139B,

    CH_8130,

    CH_8139C,

    CH_8100,

    CH_8100B_8139D,

    CH_8101,

} chip_t;

enum chip_flags {

    HasHltClk = (1 << 0),

    HasLWake = (1 << 1),

};

#define HW_REVID(b30, b29, b28, b27, b26, b23, b22) \

    (b30<<30 | b29<<29 | b28<<28 | b27<<27 | b26<<26 | b23<<23 | b22<<22)

#define HW_REVID_MASK    HW_REVID(1, 1, 1, 1, 1, 1, 1)

/* Size is 64 * 16bit words */

#define EEPROM_9346_ADDR_BITS 6

#define EEPROM_9346_SIZE  (1 << EEPROM_9346_ADDR_BITS)

#define EEPROM_9346_ADDR_MASK (EEPROM_9346_SIZE - 1)

enum Chip9346Operation

{

    Chip9346_op_mask = 0xc0,          /* 10 zzzzzz */

    Chip9346_op_read = 0x80,          /* 10 AAAAAA */

    Chip9346_op_write = 0x40,         /* 01 AAAAAA D(15)..D(0) */

    Chip9346_op_ext_mask = 0xf0,      /* 11 zzzzzz */

    Chip9346_op_write_enable = 0x30,  /* 00 11zzzz */

    Chip9346_op_write_all = 0x10,     /* 00 01zzzz */

    Chip9346_op_write_disable = 0x00, /* 00 00zzzz */

};

enum Chip9346Mode

{

    Chip9346_none = 0,

    Chip9346_enter_command_mode,

    Chip9346_read_command,

    Chip9346_data_read,      /* from output register */

    Chip9346_data_write,     /* to input register, then to contents at specified address */

    Chip9346_data_write_all, /* to input register, then filling contents */

};

typedef struct EEprom9346

{

    uint16_t contents[EEPROM_9346_SIZE];

    int      mode;

    uint32_t tick;

    uint8_t  address;

    uint16_t input;

    uint16_t output;

    uint8_t eecs;

    uint8_t eesk;

    uint8_t eedi;

    uint8_t eedo;

} EEprom9346;

typedef struct RTL8139State {

    uint8_t phys[8]; /* mac address */

    uint8_t mult[8]; /* multicast mask array */

    uint32_t TxStatus[4]; /* TxStatus0 */

    uint32_t TxAddr[4];   /* TxAddr0 */

    uint32_t RxBuf;       /* Receive buffer */

    uint32_t RxBufferSize;/* internal variable, receive ring buffer size in C mode */

    uint32_t RxBufPtr;

    uint32_t RxBufAddr;

    uint16_t IntrStatus;

    uint16_t IntrMask;

    uint32_t TxConfig;

    uint32_t RxConfig;

    uint32_t RxMissed;

    uint16_t CSCR;

    uint8_t  Cfg9346;

    uint8_t  Config0;

    uint8_t  Config1;

    uint8_t  Config3;

    uint8_t  Config4;

    uint8_t  Config5;

    uint8_t  clock_enabled;

    uint8_t  bChipCmdState;

    uint16_t MultiIntr;

    uint16_t BasicModeCtrl;

    uint16_t BasicModeStatus;

    uint16_t NWayAdvert;

    uint16_t NWayLPAR;

    uint16_t NWayExpansion;

    uint16_t CpCmd;

    uint8_t  TxThresh;

    int irq;

    PCIDevice *pci_dev;

    VLANClientState *vc;

    uint8_t macaddr[6];

    int rtl8139_mmio_io_addr;

    /* C ring mode */

    uint32_t   currTxDesc;

    /* C+ mode */

    uint32_t   currCPlusRxDesc;

    uint32_t   currCPlusTxDesc;

    uint32_t   RxRingAddrLO;

    uint32_t   RxRingAddrHI;

    EEprom9346 eeprom;

} RTL8139State;

void prom9346_decode_command(EEprom9346 *eeprom, uint8_t command)

{

#if defined(DEBUG_RTL8139)

    printf("RTL8139: eeprom command 0x%02x\n", command);

#endif

    switch (command & Chip9346_op_mask)

    {

        case Chip9346_op_read:

        {

            eeprom->address = command & EEPROM_9346_ADDR_MASK;

            eeprom->output = eeprom->contents[eeprom->address];

            eeprom->eedo = 0;

            eeprom->tick = 0;

            eeprom->mode = Chip9346_data_read;

#if defined(DEBUG_RTL8139)

            printf("RTL8139: eeprom read from address 0x%02x data=0x%04x\n",

                   eeprom->address, eeprom->output);

#endif

        }

        break;

        case Chip9346_op_write:

        {

            eeprom->address = command & EEPROM_9346_ADDR_MASK;

            eeprom->input = 0;

            eeprom->tick = 0;

            eeprom->mode = Chip9346_none; /* Chip9346_data_write */

#if defined(DEBUG_RTL8139)

            printf("RTL8139: eeprom begin write to address 0x%02x\n",

                   eeprom->address);

#endif

        }

        break;

        default:

            eeprom->mode = Chip9346_none;

            switch (command & Chip9346_op_ext_mask)

            {

                case Chip9346_op_write_enable:

#if defined(DEBUG_RTL8139)

                    printf("RTL8139: eeprom write enabled\n");

#endif

                    break;

                case Chip9346_op_write_all:

#if defined(DEBUG_RTL8139)

                    printf("RTL8139: eeprom begin write all\n");

#endif

                    break;

                case Chip9346_op_write_disable:

#if defined(DEBUG_RTL8139)

                    printf("RTL8139: eeprom write disabled\n");

#endif

                    break;

            }

            break;

    }

}

void prom9346_shift_clock(EEprom9346 *eeprom)

{

    int bit = eeprom->eedi?1:0;

    ++ eeprom->tick;

#if defined(DEBUG_RTL8139)

    printf("eeprom: tick %d eedi=%d eedo=%d\n", eeprom->tick, eeprom->eedi, eeprom->eedo);

#endif

    switch (eeprom->mode)

    {

        case Chip9346_enter_command_mode:

            if (bit)

            {

                eeprom->mode = Chip9346_read_command;

                eeprom->tick = 0;

                eeprom->input = 0;

#if defined(DEBUG_RTL8139)

                printf("eeprom: +++ synchronized, begin command read\n");

#endif

            }

            break;

        case Chip9346_read_command:

            eeprom->input = (eeprom->input << 1) | (bit & 1);

            if (eeprom->tick == 8)

            {

                prom9346_decode_command(eeprom, eeprom->input & 0xff);

            }

            break;

        case Chip9346_data_read:

            eeprom->eedo = (eeprom->output & 0x8000)?1:0;

            eeprom->output <<= 1;

            if (eeprom->tick == 16)

            {

                ++eeprom->address;

                eeprom->address &= EEPROM_9346_ADDR_MASK;

                eeprom->output = eeprom->contents[eeprom->address];

                eeprom->tick = 0;

#if defined(DEBUG_RTL8139)

                printf("eeprom: +++ read next address 0x%02x data=0x%04x\n",

                       eeprom->address, eeprom->output);

#endif

            }

            break;

        case Chip9346_data_write:

            eeprom->input = (eeprom->input << 1) | (bit & 1);

            if (eeprom->tick == 16)

            {

#if defined(DEBUG_RTL8139)

            printf("RTL8139: eeprom write to address 0x%02x data=0x%04x\n",

                   eeprom->address, eeprom->input);

#endif

                eeprom->contents[eeprom->address] = eeprom->input;

                eeprom->mode = Chip9346_none; /* waiting for next command after CS cycle */

                eeprom->tick = 0;

                eeprom->input = 0;

            }

            break;

        case Chip9346_data_write_all:

            eeprom->input = (eeprom->input << 1) | (bit & 1);

            if (eeprom->tick == 16)

            {

                int i;

                for (i = 0; i < EEPROM_9346_SIZE; i++)

                {

                    eeprom->contents[i] = eeprom->input;

                }

#if defined(DEBUG_RTL8139)

                printf("RTL8139: eeprom filled with data=0x%04x\n",

                       eeprom->input);

#endif

                eeprom->mode = Chip9346_enter_command_mode;

                eeprom->tick = 0;

                eeprom->input = 0;

            }

            break;

        default:

            break;

    }

}

int prom9346_get_wire(RTL8139State *s)

{

    EEprom9346 *eeprom = &s->eeprom;

    if (!eeprom->eecs)

        return 0;

    return eeprom->eedo;

}

void prom9346_set_wire(RTL8139State *s, int eecs, int eesk, int eedi)

{

    EEprom9346 *eeprom = &s->eeprom;

    uint8_t old_eecs = eeprom->eecs;

    uint8_t old_eesk = eeprom->eesk;

    eeprom->eecs = eecs;

    eeprom->eesk = eesk;

    eeprom->eedi = eedi;

#if defined(DEBUG_RTL8139)

    printf("eeprom: +++ wires CS=%d SK=%d DI=%d DO=%d\n", eeprom->eecs, eeprom->eesk, eeprom->eedi, eeprom->eedo);

#endif

    if (!old_eecs && eecs)

    {

        /* Synchronize start */

        eeprom->tick = 0;

        eeprom->input = 0;

        eeprom->output = 0;

        eeprom->mode = Chip9346_enter_command_mode;

#if defined(DEBUG_RTL8139)

        printf("=== eeprom: begin access, enter command mode\n");

#endif

    }

    if (!eecs)

    {

#if defined(DEBUG_RTL8139)

        printf("=== eeprom: end access\n");

#endif

        return;

    }

    if (!old_eesk && eesk)

    {

        /* SK front rules */

        prom9346_shift_clock(eeprom);

    }

}

static void rtl8139_update_irq(RTL8139State *s)

{

    int isr;

    isr = (s->IntrStatus & s->IntrMask) & 0xffff;

#if defined(DEBUG_RTL8139)

    printf("RTL8139: Set IRQ line %d to %d (%04x %04x)\n",

       s->irq, isr ? 1 : 0, s->IntrStatus, s->IntrMask);

#endif

    if (s->irq == 16) {

        /* PCI irq */

        pci_set_irq(s->pci_dev, 0, (isr != 0));

    } else {

        /* ISA irq */

        pic_set_irq(s->irq, (isr != 0));

    }

}

#define POLYNOMIAL 0x04c11db6

/* From FreeBSD */

/* XXX: optimize */

static int compute_mcast_idx(const uint8_t *ep)

{

    uint32_t crc;

    int carry, i, j;

    uint8_t b;

    crc = 0xffffffff;

    for (i = 0; i < 6; i++) {

        b = *ep++;

        for (j = 0; j < 8; j++) {

            carry = ((crc & 0x80000000L) ? 1 : 0) ^ (b & 0x01);

            crc <<= 1;

            b >>= 1;

            if (carry)

                crc = ((crc ^ POLYNOMIAL) | carry);

        }

    }

    return (crc >> 26);

}

static int rtl8139_RxWrap(RTL8139State *s)

{

    /* wrapping enabled; assume 1.5k more buffer space if size < 65536 */

    return (s->RxConfig & (1 << 7));

}

static int rtl8139_receiver_enabled(RTL8139State *s)

{

    return s->bChipCmdState & CmdRxEnb;

}

static int rtl8139_transmitter_enabled(RTL8139State *s)

{

    return s->bChipCmdState & CmdTxEnb;

}

static int rtl8139_cp_receiver_enabled(RTL8139State *s)

{

    return s->CpCmd & CPlusRxEnb;

}

static int rtl8139_cp_transmitter_enabled(RTL8139State *s)

{

    return s->CpCmd & CPlusTxEnb;

}

static void rtl8139_write_buffer(RTL8139State *s, const void *buf, int size)

{

    if (s->RxBufAddr + size > s->RxBufferSize)

    {

        int wrapped = MOD2(s->RxBufAddr + size, s->RxBufferSize);

        /* write packet data */

        if (wrapped && s->RxBufferSize < 65536 && !rtl8139_RxWrap(s))

        {

    #if defined(DEBUG_RTL8139)

            printf(">>> RTL8139: rx packet wrapped in buffer at %d\n", size-wrapped);

    #endif

            if (size > wrapped)

            {

                cpu_physical_memory_write( s->RxBuf + s->RxBufAddr,

                                           buf, size-wrapped );

            }

            /* reset buffer pointer */

            s->RxBufAddr = 0;

            cpu_physical_memory_write( s->RxBuf + s->RxBufAddr,

                                       buf + (size-wrapped), wrapped );

            s->RxBufAddr = wrapped;

            return;

        }

    }

    /* non-wrapping path or overwrapping enabled */

    cpu_physical_memory_write( s->RxBuf + s->RxBufAddr, buf, size );

    s->RxBufAddr += size;

}

#define MIN_BUF_SIZE 60

static inline target_phys_addr_t rtl8139_addr64(uint32_t low, uint32_t high)

{

#if TARGET_PHYS_ADDR_BITS > 32

    return low | ((target_phys_addr_t)high << 32);

#else

    return low;

#endif

}

static int rtl8139_can_receive(void *opaque)

{

    RTL8139State *s = opaque;

    int avail;

    /* Recieve (drop) packets if card is disabled.  */

    if (!s->clock_enabled)

      return 1;

    if (!rtl8139_receiver_enabled(s))

      return 1;

    if (rtl8139_cp_receiver_enabled(s)) {

        /* ??? Flow control not implemented in c+ mode.

           This is a hack to work around slirp deficiencies anyway.  */

        return 1;

    } else {

        avail = MOD2(s->RxBufferSize + s->RxBufPtr - s->RxBufAddr,

                     s->RxBufferSize);

        return (avail == 0 || avail >= 1514);

    }

}

static void rtl8139_receive(void *opaque, const uint8_t *buf, int size)

{

    RTL8139State *s = opaque;

    uint32_t packet_header = 0;

    uint8_t buf1[60];

    static const uint8_t broadcast_macaddr[6] = 

        { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };

#if defined(DEBUG_RTL8139)

    printf(">>> RTL8139: received len=%d\n", size);

#endif

    /* test if board clock is stopped */

    if (!s->clock_enabled)

    {

#if defined(DEBUG_RTL8139)

        printf("RTL8139: stopped ==========================\n");

#endif

        return;

    }

    /* first check if receiver is enabled */

    if (!rtl8139_receiver_enabled(s))

    {

#if defined(DEBUG_RTL8139)

        printf("RTL8139: receiver disabled ================\n");

#endif

        return;

    }

    /* XXX: check this */

    if (s->RxConfig & AcceptAllPhys) {

        /* promiscuous: receive all */

#if defined(DEBUG_RTL8139)

        printf(">>> RTL8139: packet received in promiscuous mode\n");

#endif

    } else {

        if (!memcmp(buf,  broadcast_macaddr, 6)) {

            /* broadcast address */

            if (!(s->RxConfig & AcceptBroadcast))

            {

#if defined(DEBUG_RTL8139)

                printf(">>> RTL8139: broadcast packet rejected\n");

#endif

                return;

            }

            packet_header |= RxBroadcast;

#if defined(DEBUG_RTL8139)

            printf(">>> RTL8139: broadcast packet received\n");

#endif

        } else if (buf[0] & 0x01) {

            /* multicast */

            if (!(s->RxConfig & AcceptMulticast))

            {

#if defined(DEBUG_RTL8139)

                printf(">>> RTL8139: multicast packet rejected\n");

#endif

                return;

            }

            int mcast_idx = compute_mcast_idx(buf);

            if (!(s->mult[mcast_idx >> 3] & (1 << (mcast_idx & 7))))

            {

#if defined(DEBUG_RTL8139)

                printf(">>> RTL8139: multicast address mismatch\n");

#endif

                return;

            }

            packet_header |= RxMulticast;

#if defined(DEBUG_RTL8139)

            printf(">>> RTL8139: multicast packet received\n");

#endif

        } else if (s->phys[0] == buf[0] &&

                   s->phys[1] == buf[1] &&                   

                   s->phys[2] == buf[2] &&            

                   s->phys[3] == buf[3] &&            

                   s->phys[4] == buf[4] &&            

                   s->phys[5] == buf[5]) {

            /* match */

            if (!(s->RxConfig & AcceptMyPhys))

            {

#if defined(DEBUG_RTL8139)

                printf(">>> RTL8139: rejecting physical address matching packet\n");

#endif

                return;

            }

            packet_header |= RxPhysical;

#if defined(DEBUG_RTL8139)

            printf(">>> RTL8139: physical address matching packet received\n");

#endif

        } else {

#if defined(DEBUG_RTL8139)

                printf(">>> RTL8139: unknown packet\n");

#endif

            return;

        }

    }

    /* if too small buffer, then expand it */

    if (size < MIN_BUF_SIZE) {

        memcpy(buf1, buf, size);

        memset(buf1 + size, 0, MIN_BUF_SIZE - size);

        buf = buf1;

        size = MIN_BUF_SIZE;

    }

    if (rtl8139_cp_receiver_enabled(s))

    {

#if defined(DEBUG_RTL8139)

        printf("RTL8139: in C+ Rx mode ================\n");

#endif