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/*

 * QEMU Xilinx GEM emulation

 *

 * Copyright (c) 2011 Xilinx, Inc.

 *

 * 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.

 */

#include <zlib.h> /* For crc32 */

#include "sysbus.h"

#include "net.h"

#include "net/checksum.h"

#ifdef CADENCE_GEM_ERR_DEBUG

#define DB_PRINT(...) do { \

    fprintf(stderr,  ": %s: ", __func__); \

    fprintf(stderr, ## __VA_ARGS__); \

    } while (0);

#else

    #define DB_PRINT(...)

#endif

#define GEM_NWCTRL        (0x00000000/4) /* Network Control reg */

#define GEM_NWCFG         (0x00000004/4) /* Network Config reg */

#define GEM_NWSTATUS      (0x00000008/4) /* Network Status reg */

#define GEM_USERIO        (0x0000000C/4) /* User IO reg */

#define GEM_DMACFG        (0x00000010/4) /* DMA Control reg */

#define GEM_TXSTATUS      (0x00000014/4) /* TX Status reg */

#define GEM_RXQBASE       (0x00000018/4) /* RX Q Base address reg */

#define GEM_TXQBASE       (0x0000001C/4) /* TX Q Base address reg */

#define GEM_RXSTATUS      (0x00000020/4) /* RX Status reg */

#define GEM_ISR           (0x00000024/4) /* Interrupt Status reg */

#define GEM_IER           (0x00000028/4) /* Interrupt Enable reg */

#define GEM_IDR           (0x0000002C/4) /* Interrupt Disable reg */

#define GEM_IMR           (0x00000030/4) /* Interrupt Mask reg */

#define GEM_PHYMNTNC      (0x00000034/4) /* Phy Maintaince reg */

#define GEM_RXPAUSE       (0x00000038/4) /* RX Pause Time reg */

#define GEM_TXPAUSE       (0x0000003C/4) /* TX Pause Time reg */

#define GEM_TXPARTIALSF   (0x00000040/4) /* TX Partial Store and Forward */

#define GEM_RXPARTIALSF   (0x00000044/4) /* RX Partial Store and Forward */

#define GEM_HASHLO        (0x00000080/4) /* Hash Low address reg */

#define GEM_HASHHI        (0x00000084/4) /* Hash High address reg */

#define GEM_SPADDR1LO     (0x00000088/4) /* Specific addr 1 low reg */

#define GEM_SPADDR1HI     (0x0000008C/4) /* Specific addr 1 high reg */

#define GEM_SPADDR2LO     (0x00000090/4) /* Specific addr 2 low reg */

#define GEM_SPADDR2HI     (0x00000094/4) /* Specific addr 2 high reg */

#define GEM_SPADDR3LO     (0x00000098/4) /* Specific addr 3 low reg */

#define GEM_SPADDR3HI     (0x0000009C/4) /* Specific addr 3 high reg */

#define GEM_SPADDR4LO     (0x000000A0/4) /* Specific addr 4 low reg */

#define GEM_SPADDR4HI     (0x000000A4/4) /* Specific addr 4 high reg */

#define GEM_TIDMATCH1     (0x000000A8/4) /* Type ID1 Match reg */

#define GEM_TIDMATCH2     (0x000000AC/4) /* Type ID2 Match reg */

#define GEM_TIDMATCH3     (0x000000B0/4) /* Type ID3 Match reg */

#define GEM_TIDMATCH4     (0x000000B4/4) /* Type ID4 Match reg */

#define GEM_WOLAN         (0x000000B8/4) /* Wake on LAN reg */

#define GEM_IPGSTRETCH    (0x000000BC/4) /* IPG Stretch reg */

#define GEM_SVLAN         (0x000000C0/4) /* Stacked VLAN reg */

#define GEM_MODID         (0x000000FC/4) /* Module ID reg */

#define GEM_OCTTXLO       (0x00000100/4) /* Octects transmitted Low reg */

#define GEM_OCTTXHI       (0x00000104/4) /* Octects transmitted High reg */

#define GEM_TXCNT         (0x00000108/4) /* Error-free Frames transmitted */

#define GEM_TXBCNT        (0x0000010C/4) /* Error-free Broadcast Frames */

#define GEM_TXMCNT        (0x00000110/4) /* Error-free Multicast Frame */

#define GEM_TXPAUSECNT    (0x00000114/4) /* Pause Frames Transmitted */

#define GEM_TX64CNT       (0x00000118/4) /* Error-free 64 TX */

#define GEM_TX65CNT       (0x0000011C/4) /* Error-free 65-127 TX */

#define GEM_TX128CNT      (0x00000120/4) /* Error-free 128-255 TX */

#define GEM_TX256CNT      (0x00000124/4) /* Error-free 256-511 */

#define GEM_TX512CNT      (0x00000128/4) /* Error-free 512-1023 TX */

#define GEM_TX1024CNT     (0x0000012C/4) /* Error-free 1024-1518 TX */

#define GEM_TX1519CNT     (0x00000130/4) /* Error-free larger than 1519 TX */

#define GEM_TXURUNCNT     (0x00000134/4) /* TX under run error counter */

#define GEM_SINGLECOLLCNT (0x00000138/4) /* Single Collision Frames */

#define GEM_MULTCOLLCNT   (0x0000013C/4) /* Multiple Collision Frames */

#define GEM_EXCESSCOLLCNT (0x00000140/4) /* Excessive Collision Frames */

#define GEM_LATECOLLCNT   (0x00000144/4) /* Late Collision Frames */

#define GEM_DEFERTXCNT    (0x00000148/4) /* Deferred Transmission Frames */

#define GEM_CSENSECNT     (0x0000014C/4) /* Carrier Sense Error Counter */

#define GEM_OCTRXLO       (0x00000150/4) /* Octects Received register Low */

#define GEM_OCTRXHI       (0x00000154/4) /* Octects Received register High */

#define GEM_RXCNT         (0x00000158/4) /* Error-free Frames Received */

#define GEM_RXBROADCNT    (0x0000015C/4) /* Error-free Broadcast Frames RX */

#define GEM_RXMULTICNT    (0x00000160/4) /* Error-free Multicast Frames RX */

#define GEM_RXPAUSECNT    (0x00000164/4) /* Pause Frames Received Counter */

#define GEM_RX64CNT       (0x00000168/4) /* Error-free 64 byte Frames RX */

#define GEM_RX65CNT       (0x0000016C/4) /* Error-free 65-127B Frames RX */

#define GEM_RX128CNT      (0x00000170/4) /* Error-free 128-255B Frames RX */

#define GEM_RX256CNT      (0x00000174/4) /* Error-free 256-512B Frames RX */

#define GEM_RX512CNT      (0x00000178/4) /* Error-free 512-1023B Frames RX */

#define GEM_RX1024CNT     (0x0000017C/4) /* Error-free 1024-1518B Frames RX */

#define GEM_RX1519CNT     (0x00000180/4) /* Error-free 1519-max Frames RX */

#define GEM_RXUNDERCNT    (0x00000184/4) /* Undersize Frames Received */

#define GEM_RXOVERCNT     (0x00000188/4) /* Oversize Frames Received */

#define GEM_RXJABCNT      (0x0000018C/4) /* Jabbers Received Counter */

#define GEM_RXFCSCNT      (0x00000190/4) /* Frame Check seq. Error Counter */

#define GEM_RXLENERRCNT   (0x00000194/4) /* Length Field Error Counter */

#define GEM_RXSYMERRCNT   (0x00000198/4) /* Symbol Error Counter */

#define GEM_RXALIGNERRCNT (0x0000019C/4) /* Alignment Error Counter */

#define GEM_RXRSCERRCNT   (0x000001A0/4) /* Receive Resource Error Counter */

#define GEM_RXORUNCNT     (0x000001A4/4) /* Receive Overrun Counter */

#define GEM_RXIPCSERRCNT  (0x000001A8/4) /* IP header Checksum Error Counter */

#define GEM_RXTCPCCNT     (0x000001AC/4) /* TCP Checksum Error Counter */

#define GEM_RXUDPCCNT     (0x000001B0/4) /* UDP Checksum Error Counter */

#define GEM_1588S         (0x000001D0/4) /* 1588 Timer Seconds */

#define GEM_1588NS        (0x000001D4/4) /* 1588 Timer Nanoseconds */

#define GEM_1588ADJ       (0x000001D8/4) /* 1588 Timer Adjust */

#define GEM_1588INC       (0x000001DC/4) /* 1588 Timer Increment */

#define GEM_PTPETXS       (0x000001E0/4) /* PTP Event Frame Transmitted (s) */

#define GEM_PTPETXNS      (0x000001E4/4) /* PTP Event Frame Transmitted (ns) */

#define GEM_PTPERXS       (0x000001E8/4) /* PTP Event Frame Received (s) */

#define GEM_PTPERXNS      (0x000001EC/4) /* PTP Event Frame Received (ns) */

#define GEM_PTPPTXS       (0x000001E0/4) /* PTP Peer Frame Transmitted (s) */

#define GEM_PTPPTXNS      (0x000001E4/4) /* PTP Peer Frame Transmitted (ns) */

#define GEM_PTPPRXS       (0x000001E8/4) /* PTP Peer Frame Received (s) */

#define GEM_PTPPRXNS      (0x000001EC/4) /* PTP Peer Frame Received (ns) */

/* Design Configuration Registers */

#define GEM_DESCONF       (0x00000280/4)

#define GEM_DESCONF2      (0x00000284/4)

#define GEM_DESCONF3      (0x00000288/4)

#define GEM_DESCONF4      (0x0000028C/4)

#define GEM_DESCONF5      (0x00000290/4)

#define GEM_DESCONF6      (0x00000294/4)

#define GEM_DESCONF7      (0x00000298/4)

#define GEM_MAXREG        (0x00000640/4) /* Last valid GEM address */

/*****************************************/

#define GEM_NWCTRL_TXSTART     0x00000200 /* Transmit Enable */

#define GEM_NWCTRL_TXENA       0x00000008 /* Transmit Enable */

#define GEM_NWCTRL_RXENA       0x00000004 /* Receive Enable */

#define GEM_NWCTRL_LOCALLOOP   0x00000002 /* Local Loopback */

#define GEM_NWCFG_STRIP_FCS    0x00020000 /* Strip FCS field */

#define GEM_NWCFG_LERR_DISC    0x00010000 /* Discard RX frames with lenth err */

#define GEM_NWCFG_BUFF_OFST_M  0x0000C000 /* Receive buffer offset mask */

#define GEM_NWCFG_BUFF_OFST_S  14         /* Receive buffer offset shift */

#define GEM_NWCFG_UCAST_HASH   0x00000080 /* accept unicast if hash match */

#define GEM_NWCFG_MCAST_HASH   0x00000040 /* accept multicast if hash match */

#define GEM_NWCFG_BCAST_REJ    0x00000020 /* Reject broadcast packets */

#define GEM_NWCFG_PROMISC      0x00000010 /* Accept all packets */

#define GEM_DMACFG_RBUFSZ_M    0x007F0000 /* DMA RX Buffer Size mask */

#define GEM_DMACFG_RBUFSZ_S    16         /* DMA RX Buffer Size shift */

#define GEM_DMACFG_RBUFSZ_MUL  64         /* DMA RX Buffer Size multiplier */

#define GEM_DMACFG_TXCSUM_OFFL 0x00000800 /* Transmit checksum offload */

#define GEM_TXSTATUS_TXCMPL    0x00000020 /* Transmit Complete */

#define GEM_TXSTATUS_USED      0x00000001 /* sw owned descriptor encountered */

#define GEM_RXSTATUS_FRMRCVD   0x00000002 /* Frame received */

#define GEM_RXSTATUS_NOBUF     0x00000001 /* Buffer unavailable */

/* GEM_ISR GEM_IER GEM_IDR GEM_IMR */

#define GEM_INT_TXCMPL        0x00000080 /* Transmit Complete */

#define GEM_INT_TXUSED         0x00000008

#define GEM_INT_RXUSED         0x00000004

#define GEM_INT_RXCMPL        0x00000002

#define GEM_PHYMNTNC_OP_R      0x20000000 /* read operation */

#define GEM_PHYMNTNC_OP_W      0x10000000 /* write operation */

#define GEM_PHYMNTNC_ADDR      0x0F800000 /* Address bits */

#define GEM_PHYMNTNC_ADDR_SHFT 23

#define GEM_PHYMNTNC_REG       0x007C0000 /* register bits */

#define GEM_PHYMNTNC_REG_SHIFT 18

/* Marvell PHY definitions */

#define BOARD_PHY_ADDRESS    23 /* PHY address we will emulate a device at */

#define PHY_REG_CONTROL      0

#define PHY_REG_STATUS       1

#define PHY_REG_PHYID1       2

#define PHY_REG_PHYID2       3

#define PHY_REG_ANEGADV      4

#define PHY_REG_LINKPABIL    5

#define PHY_REG_ANEGEXP      6

#define PHY_REG_NEXTP        7

#define PHY_REG_LINKPNEXTP   8

#define PHY_REG_100BTCTRL    9

#define PHY_REG_1000BTSTAT   10

#define PHY_REG_EXTSTAT      15

#define PHY_REG_PHYSPCFC_CTL 16

#define PHY_REG_PHYSPCFC_ST  17

#define PHY_REG_INT_EN       18

#define PHY_REG_INT_ST       19

#define PHY_REG_EXT_PHYSPCFC_CTL  20

#define PHY_REG_RXERR        21

#define PHY_REG_EACD         22

#define PHY_REG_LED          24

#define PHY_REG_LED_OVRD     25

#define PHY_REG_EXT_PHYSPCFC_CTL2 26

#define PHY_REG_EXT_PHYSPCFC_ST   27

#define PHY_REG_CABLE_DIAG   28

#define PHY_REG_CONTROL_RST  0x8000

#define PHY_REG_CONTROL_LOOP 0x4000

#define PHY_REG_CONTROL_ANEG 0x1000

#define PHY_REG_STATUS_LINK     0x0004

#define PHY_REG_STATUS_ANEGCMPL 0x0020

#define PHY_REG_INT_ST_ANEGCMPL 0x0800

#define PHY_REG_INT_ST_LINKC    0x0400

#define PHY_REG_INT_ST_ENERGY   0x0010

/***********************************************************************/

#define GEM_RX_REJECT  1

#define GEM_RX_ACCEPT  0

/***********************************************************************/

#define DESC_1_USED 0x80000000

#define DESC_1_LENGTH 0x00001FFF

#define DESC_1_TX_WRAP 0x40000000

#define DESC_1_TX_LAST 0x00008000

#define DESC_0_RX_WRAP 0x00000002

#define DESC_0_RX_OWNERSHIP 0x00000001

#define DESC_1_RX_SOF 0x00004000

#define DESC_1_RX_EOF 0x00008000

static inline unsigned tx_desc_get_buffer(unsigned *desc)

{

    return desc[0];

}

static inline unsigned tx_desc_get_used(unsigned *desc)

{

    return (desc[1] & DESC_1_USED) ? 1 : 0;

}

static inline void tx_desc_set_used(unsigned *desc)

{

    desc[1] |= DESC_1_USED;

}

static inline unsigned tx_desc_get_wrap(unsigned *desc)

{

    return (desc[1] & DESC_1_TX_WRAP) ? 1 : 0;

}

static inline unsigned tx_desc_get_last(unsigned *desc)

{

    return (desc[1] & DESC_1_TX_LAST) ? 1 : 0;

}

static inline unsigned tx_desc_get_length(unsigned *desc)

{

    return desc[1] & DESC_1_LENGTH;

}

static inline void print_gem_tx_desc(unsigned *desc)

{

    DB_PRINT("TXDESC:\n");

    DB_PRINT("bufaddr: 0x%08x\n", *desc);

    DB_PRINT("used_hw: %d\n", tx_desc_get_used(desc));

    DB_PRINT("wrap:    %d\n", tx_desc_get_wrap(desc));

    DB_PRINT("last:    %d\n", tx_desc_get_last(desc));

    DB_PRINT("length:  %d\n", tx_desc_get_length(desc));

}

static inline unsigned rx_desc_get_buffer(unsigned *desc)

{

    return desc[0] & ~0x3UL;

}

static inline unsigned rx_desc_get_wrap(unsigned *desc)

{

    return desc[0] & DESC_0_RX_WRAP ? 1 : 0;

}

static inline unsigned rx_desc_get_ownership(unsigned *desc)

{

    return desc[0] & DESC_0_RX_OWNERSHIP ? 1 : 0;

}

static inline void rx_desc_set_ownership(unsigned *desc)

{

    desc[0] |= DESC_0_RX_OWNERSHIP;

}

static inline void rx_desc_set_sof(unsigned *desc)

{

    desc[1] |= DESC_1_RX_SOF;

}

static inline void rx_desc_set_eof(unsigned *desc)

{

    desc[1] |= DESC_1_RX_EOF;

}

static inline void rx_desc_set_length(unsigned *desc, unsigned len)

{

    desc[1] &= ~DESC_1_LENGTH;

    desc[1] |= len;

}

typedef struct {

    SysBusDevice busdev;

    MemoryRegion iomem;

    NICState *nic;

    NICConf conf;

    qemu_irq irq;

    /* GEM registers backing store */

    uint32_t regs[GEM_MAXREG];

    /* Mask of register bits which are write only */

    uint32_t regs_wo[GEM_MAXREG];

    /* Mask of register bits which are read only */

    uint32_t regs_ro[GEM_MAXREG];

    /* Mask of register bits which are clear on read */

    uint32_t regs_rtc[GEM_MAXREG];

    /* Mask of register bits which are write 1 to clear */

    uint32_t regs_w1c[GEM_MAXREG];

    /* PHY registers backing store */

    uint16_t phy_regs[32];

    uint8_t phy_loop; /* Are we in phy loopback? */

    /* The current DMA descriptor pointers */

    target_phys_addr_t rx_desc_addr;

    target_phys_addr_t tx_desc_addr;

} GemState;

/* The broadcast MAC address: 0xFFFFFFFFFFFF */

const uint8_t broadcast_addr[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

/*

 * gem_init_register_masks:

 * One time initialization.

 * Set masks to identify which register bits have magical clear properties

 */

static void gem_init_register_masks(GemState *s)

{

    /* Mask of register bits which are read only*/

    memset(&s->regs_ro[0], 0, sizeof(s->regs_ro));

    s->regs_ro[GEM_NWCTRL]   = 0xFFF80000;

    s->regs_ro[GEM_NWSTATUS] = 0xFFFFFFFF;

    s->regs_ro[GEM_DMACFG]   = 0xFE00F000;

    s->regs_ro[GEM_TXSTATUS] = 0xFFFFFE08;

    s->regs_ro[GEM_RXQBASE]  = 0x00000003;

    s->regs_ro[GEM_TXQBASE]  = 0x00000003;

    s->regs_ro[GEM_RXSTATUS] = 0xFFFFFFF0;

    s->regs_ro[GEM_ISR]      = 0xFFFFFFFF;

    s->regs_ro[GEM_IMR]      = 0xFFFFFFFF;

    s->regs_ro[GEM_MODID]    = 0xFFFFFFFF;

    /* Mask of register bits which are clear on read */

    memset(&s->regs_rtc[0], 0, sizeof(s->regs_rtc));

    s->regs_rtc[GEM_ISR]      = 0xFFFFFFFF;

    /* Mask of register bits which are write 1 to clear */

    memset(&s->regs_w1c[0], 0, sizeof(s->regs_w1c));

    s->regs_w1c[GEM_TXSTATUS] = 0x000001F7;

    s->regs_w1c[GEM_RXSTATUS] = 0x0000000F;

    /* Mask of register bits which are write only */

    memset(&s->regs_wo[0], 0, sizeof(s->regs_wo));

    s->regs_wo[GEM_NWCTRL]   = 0x00073E60;

    s->regs_wo[GEM_IER]      = 0x07FFFFFF;

    s->regs_wo[GEM_IDR]      = 0x07FFFFFF;

}

/*

 * phy_update_link:

 * Make the emulated PHY link state match the QEMU "interface" state.

 */

static void phy_update_link(GemState *s)

{

    DB_PRINT("down %d\n", s->nic->nc.link_down);

    /* Autonegotiation status mirrors link status.  */

    if (s->nic->nc.link_down) {

        s->phy_regs[PHY_REG_STATUS] &= ~(PHY_REG_STATUS_ANEGCMPL |

                                         PHY_REG_STATUS_LINK);

        s->phy_regs[PHY_REG_INT_ST] |= PHY_REG_INT_ST_LINKC;

    } else {

        s->phy_regs[PHY_REG_STATUS] |= (PHY_REG_STATUS_ANEGCMPL |

                                         PHY_REG_STATUS_LINK);

        s->phy_regs[PHY_REG_INT_ST] |= (PHY_REG_INT_ST_LINKC |

                                        PHY_REG_INT_ST_ANEGCMPL |

                                        PHY_REG_INT_ST_ENERGY);

    }

}

static int gem_can_receive(VLANClientState *nc)

{

    GemState *s;

    s = DO_UPCAST(NICState, nc, nc)->opaque;

    DB_PRINT("\n");

    /* Do nothing if receive is not enabled. */

    if (!(s->regs[GEM_NWCTRL] & GEM_NWCTRL_RXENA)) {

        return 0;

    }

    return 1;

}

/*

 * gem_update_int_status:

 * Raise or lower interrupt based on current status.

 */

static void gem_update_int_status(GemState *s)

{

    uint32_t new_interrupts = 0;

    /* Packet transmitted ? */

    if (s->regs[GEM_TXSTATUS] & GEM_TXSTATUS_TXCMPL) {

        new_interrupts |= GEM_INT_TXCMPL;

    }

    /* End of TX ring ? */

    if (s->regs[GEM_TXSTATUS] & GEM_TXSTATUS_USED) {

        new_interrupts |= GEM_INT_TXUSED;

    }

    /* Frame received ? */

    if (s->regs[GEM_RXSTATUS] & GEM_RXSTATUS_FRMRCVD) {

        new_interrupts |= GEM_INT_RXCMPL;

    }

    /* RX ring full ? */

    if (s->regs[GEM_RXSTATUS] & GEM_RXSTATUS_NOBUF) {

        new_interrupts |= GEM_INT_RXUSED;

    }

    s->regs[GEM_ISR] |= new_interrupts & ~(s->regs[GEM_IMR]);

    if (s->regs[GEM_ISR]) {

        DB_PRINT("asserting int. (0x%08x)\n", s->regs[GEM_ISR]);

        qemu_set_irq(s->irq, 1);

    } else {

        qemu_set_irq(s->irq, 0);

    }

}

/*

 * gem_receive_updatestats:

 * Increment receive statistics.

 */

static void gem_receive_updatestats(GemState *s, const uint8_t *packet,

                                    unsigned bytes)

{

    uint64_t octets;

    /* Total octets (bytes) received */

    octets = ((uint64_t)(s->regs[GEM_OCTRXLO]) << 32) |

             s->regs[GEM_OCTRXHI];

    octets += bytes;

    s->regs[GEM_OCTRXLO] = octets >> 32;

    s->regs[GEM_OCTRXHI] = octets;

    /* Error-free Frames received */

    s->regs[GEM_RXCNT]++;

    /* Error-free Broadcast Frames counter */

    if (!memcmp(packet, broadcast_addr, 6)) {

        s->regs[GEM_RXBROADCNT]++;

    }

    /* Error-free Multicast Frames counter */

    if (packet[0] == 0x01) {

        s->regs[GEM_RXMULTICNT]++;

    }

    if (bytes <= 64) {

        s->regs[GEM_RX64CNT]++;

    } else if (bytes <= 127) {

        s->regs[GEM_RX65CNT]++;

    } else if (bytes <= 255) {

        s->regs[GEM_RX128CNT]++;

    } else if (bytes <= 511) {

        s->regs[GEM_RX256CNT]++;

    } else if (bytes <= 1023) {

        s->regs[GEM_RX512CNT]++;

    } else if (bytes <= 1518) {

        s->regs[GEM_RX1024CNT]++;

    } else {

        s->regs[GEM_RX1519CNT]++;

    }

}

/*

 * Get the MAC Address bit from the specified position

 */

static unsigned get_bit(const uint8_t *mac, unsigned bit)

{

    unsigned byte;

    byte = mac[bit / 8];

    byte >>= (bit & 0x7);

    byte &= 1;

    return byte;

}

/*

 * Calculate a GEM MAC Address hash index

 */

static unsigned calc_mac_hash(const uint8_t *mac)

{

    int index_bit, mac_bit;

    unsigned hash_index;

    hash_index = 0;

    mac_bit = 5;

    for (index_bit = 5; index_bit >= 0; index_bit--) {

        hash_index |= (get_bit(mac,  mac_bit) ^

                               get_bit(mac, mac_bit + 6) ^

                               get_bit(mac, mac_bit + 12) ^

                               get_bit(mac, mac_bit + 18) ^

                               get_bit(mac, mac_bit + 24) ^

                               get_bit(mac, mac_bit + 30) ^

                               get_bit(mac, mac_bit + 36) ^

                               get_bit(mac, mac_bit + 42)) << index_bit;

        mac_bit--;

    }

    return hash_index;

}

/*

 * gem_mac_address_filter:

 * Accept or reject this destination address?

 * Returns:

 * GEM_RX_REJECT: reject

 * GEM_RX_ACCEPT: accept

 */

static int gem_mac_address_filter(GemState *s, const uint8_t *packet)

{

    uint8_t *gem_spaddr;

    int i;

    /* Promiscuous mode? */

    if (s->regs[GEM_NWCFG] & GEM_NWCFG_PROMISC) {

        return GEM_RX_ACCEPT;

    }

    if (!memcmp(packet, broadcast_addr, 6)) {

        /* Reject broadcast packets? */

        if (s->regs[GEM_NWCFG] & GEM_NWCFG_BCAST_REJ) {

            return GEM_RX_REJECT;

        }

        return GEM_RX_ACCEPT;

    }

    /* Accept packets -w- hash match? */

    if ((packet[0] == 0x01 && (s->regs[GEM_NWCFG] & GEM_NWCFG_MCAST_HASH)) ||

        (packet[0] != 0x01 && (s->regs[GEM_NWCFG] & GEM_NWCFG_UCAST_HASH))) {

        unsigned hash_index;

        hash_index = calc_mac_hash(packet);

        if (hash_index < 32) {

            if (s->regs[GEM_HASHLO] & (1<<hash_index)) {

                return GEM_RX_ACCEPT;

            }

        } else {

            hash_index -= 32;

            if (s->regs[GEM_HASHHI] & (1<<hash_index)) {

                return GEM_RX_ACCEPT;

            }

        }

    }

    /* Check all 4 specific addresses */

    gem_spaddr = (uint8_t *)&(s->regs[GEM_SPADDR1LO]);

    for (i = 0; i < 4; i++) {

        if (!memcmp(packet, gem_spaddr, 6)) {

            return GEM_RX_ACCEPT;

        }

        gem_spaddr += 8;

    }

    /* No address match; reject the packet */

    return GEM_RX_REJECT;

}

/*

 * gem_receive:

 * Fit a packet handed to us by QEMU into the receive descriptor ring.

 */

static ssize_t gem_receive(VLANClientState *nc, const uint8_t *buf, size_t size)

{

    unsigned    desc[2];

    target_phys_addr_t packet_desc_addr, last_desc_addr;

    GemState *s;

    unsigned   rxbufsize, bytes_to_copy;

    unsigned   rxbuf_offset;

    uint8_t    rxbuf[2048];

    uint8_t   *rxbuf_ptr;

    s = DO_UPCAST(NICState, nc, nc)->opaque;

    /* Do nothing if receive is not enabled. */

    if (!(s->regs[GEM_NWCTRL] & GEM_NWCTRL_RXENA)) {

        return -1;

    }

    /* Is this destination MAC address "for us" ? */

    if (gem_mac_address_filter(s, buf) == GEM_RX_REJECT) {

        return -1;

    }

    /* Discard packets with receive length error enabled ? */

    if (s->regs[GEM_NWCFG] & GEM_NWCFG_LERR_DISC) {

        unsigned type_len;

        /* Fish the ethertype / length field out of the RX packet */

        type_len = buf[12] << 8 | buf[13];

        /* It is a length field, not an ethertype */

        if (type_len < 0x600) {

            if (size < type_len) {

                /* discard */

                return -1;

            }

        }

    }

    /*

     * Determine configured receive buffer offset (probably 0)

     */

    rxbuf_offset = (s->regs[GEM_NWCFG] & GEM_NWCFG_BUFF_OFST_M) >>

                   GEM_NWCFG_BUFF_OFST_S;

    /* The configure size of each receive buffer.  Determines how many

     * buffers needed to hold this packet.

     */

    rxbufsize = ((s->regs[GEM_DMACFG] & GEM_DMACFG_RBUFSZ_M) >>

                 GEM_DMACFG_RBUFSZ_S) * GEM_DMACFG_RBUFSZ_MUL;

    bytes_to_copy = size;

    /* Strip of FCS field ? (usually yes) */

    if (s->regs[GEM_NWCFG] & GEM_NWCFG_STRIP_FCS) {

        rxbuf_ptr = (void *)buf;

    } else {

        unsigned crc_val;

        int      crc_offset;

        /* The application wants the FCS field, which QEMU does not provide.

         * We must try and caclculate one.

         */

        memcpy(rxbuf, buf, size);

        memset(rxbuf + size, 0, sizeof(rxbuf - size));

        rxbuf_ptr = rxbuf;

        crc_val = cpu_to_le32(crc32(0, rxbuf, MAX(size, 60)));

        if (size < 60) {

            crc_offset = 60;

        } else {

            crc_offset = size;

        }

        memcpy(rxbuf + crc_offset, &crc_val, sizeof(crc_val));

        bytes_to_copy += 4;

        size += 4;

    }

    /* Pad to minimum length */

    if (size < 64) {

        size = 64;

    }

    DB_PRINT("config bufsize: %d packet size: %ld\n", rxbufsize, size);

    packet_desc_addr = s->rx_desc_addr;

    while (1) {

        DB_PRINT("read descriptor 0x%x\n", packet_desc_addr);

        /* read current descriptor */

        cpu_physical_memory_read(packet_desc_addr,

                                 (uint8_t *)&desc[0], sizeof(desc));

        /* Descriptor owned by software ? */

        if (rx_desc_get_ownership(desc) == 1) {

            DB_PRINT("descriptor 0x%x owned by sw.\n", packet_desc_addr);

            s->regs[GEM_RXSTATUS] |= GEM_RXSTATUS_NOBUF;

            /* Handle interrupt consequences */

            gem_update_int_status(s);

            return -1;

        }

        DB_PRINT("copy %d bytes to 0x%x\n", MIN(bytes_to_copy, rxbufsize),

                rx_desc_get_buffer(desc));

        /*

         * Let's have QEMU lend a helping hand.

         */

        if (rx_desc_get_buffer(desc) == 0) {

            DB_PRINT("Invalid RX buffer (NULL) for descriptor 0x%x\n",

                       packet_desc_addr);

            break;

        }

        /* Copy packet data to emulated DMA buffer */

        cpu_physical_memory_write(rx_desc_get_buffer(desc) + rxbuf_offset,

                                  rxbuf_ptr, MIN(bytes_to_copy, rxbufsize));

        bytes_to_copy -= MIN(bytes_to_copy, rxbufsize);

        rxbuf_ptr += MIN(bytes_to_copy, rxbufsize);

        if (bytes_to_copy == 0) {

            break;

        }

        /* Next descriptor */

        if (rx_desc_get_wrap(desc)) {

            packet_desc_addr = s->regs[GEM_RXQBASE];

        } else {

            packet_desc_addr += 8;

        }

    }

    DB_PRINT("set length: %ld, EOF on descriptor 0x%x\n", size,

            (unsigned)packet_desc_addr);

    /* Update last descriptor with EOF and total length */

    rx_desc_set_eof(desc);

    rx_desc_set_length(desc, size);

    cpu_physical_memory_write(packet_desc_addr,

                              (uint8_t *)&desc[0], sizeof(desc));

    /* Advance RX packet descriptor Q */

    last_desc_addr = packet_desc_addr;

    packet_desc_addr = s->rx_desc_addr;

    s->rx_desc_addr = last_desc_addr;

    if (rx_desc_get_wrap(desc)) {

        s->rx_desc_addr = s->regs[GEM_RXQBASE];

    } else {

        s->rx_desc_addr += 8;

    }

    DB_PRINT("set SOF, OWN on descriptor 0x%08x\n", packet_desc_addr);

    /* Count it */

    gem_receive_updatestats(s, buf, size);

    /* Update first descriptor (which could also be the last) */

    /* read descriptor */

    cpu_physical_memory_read(packet_desc_addr,

                             (uint8_t *)&desc[0], sizeof(desc));

    rx_desc_set_sof(desc);

    rx_desc_set_ownership(desc);

    cpu_physical_memory_write(packet_desc_addr,

                              (uint8_t *)&desc[0], sizeof(desc));

    s->regs[GEM_RXSTATUS] |= GEM_RXSTATUS_FRMRCVD;

    /* Handle interrupt consequences */

    gem_update_int_status(s);

    return size;

}

/*

 * gem_transmit_updatestats:

 * Increment transmit statistics.

 */

static void gem_transmit_updatestats(GemState *s, const uint8_t *packet,

                                     unsigned bytes)

{

    uint64_t octets;

    /* Total octets (bytes) transmitted */

    octets = ((uint64_t)(s->regs[GEM_OCTTXLO]) << 32) |

             s->regs[GEM_OCTTXHI];

    octets += bytes;

    s->regs[GEM_OCTTXLO] = octets >> 32;

    s->regs[GEM_OCTTXHI] = octets;

    /* Error-free Frames transmitted */

    s->regs[GEM_TXCNT]++;

    /* Error-free Broadcast Frames counter */

    if (!memcmp(packet, broadcast_addr, 6)) {

        s->regs[GEM_TXBCNT]++;

    }

    /* Error-free Multicast Frames counter */

    if (packet[0] == 0x01) {

        s->regs[GEM_TXMCNT]++;

    }

    if (bytes <= 64) {

        s->regs[GEM_TX64CNT]++;

    } else if (bytes <= 127) {

        s->regs[GEM_TX65CNT]++;

    } else if (bytes <= 255) {

        s->regs[GEM_TX128CNT]++;

    } else if (bytes <= 511) {

        s->regs[GEM_TX256CNT]++;

    } else if (bytes <= 1023) {

        s->regs[GEM_TX512CNT]++;

    } else if (bytes <= 1518) {

        s->regs[GEM_TX1024CNT]++;

    } else {

        s->regs[GEM_TX1519CNT]++;

    }

}

/*

 * gem_transmit:

 * Fish packets out of the descriptor ring and feed them to QEMU

 */

static void gem_transmit(GemState *s)

{

    unsigned    desc[2];

    target_phys_addr_t packet_desc_addr;

    uint8_t     tx_packet[2048];

    uint8_t     *p;

    unsigned    total_bytes;

    /* Do nothing if transmit is not enabled. */

    if (!(s->regs[GEM_NWCTRL] & GEM_NWCTRL_TXENA)) {

        return;

    }

    DB_PRINT("\n");

    /* The packet we will hand off to qemu.

     * Packets scattered across multiple descriptors are gathered to this

     * one contiguous buffer first.

     */

    p = tx_packet;

    total_bytes = 0;