u-boot中网口处理--软件部分

u-boot中DM9000驱动分析

1. CSRs和PHY reg读写。

static u16
phy_read(int reg)
{
    u16 val;

    /* Fill the phyxcer register into REG_0C */
    DM9000_iow(DM9000_EPAR, DM9000_PHY | reg);
    DM9000_iow(DM9000_EPCR, 0xc);    /* Issue phyxcer read command */
    udelay(100);        /* Wait read complete */
    DM9000_iow(DM9000_EPCR, 0x0);    /* Clear phyxcer read command */
    val = (DM9000_ior(DM9000_EPDRH) << 8) | DM9000_ior(DM9000_EPDRL);

    /* The read data keeps on REG_0D & REG_0E */
    DM9000_DBG("phy_read(%d): %d
", reg, val);
    return val;
}

static void
phy_write(int reg, u16 value)
{

    /* Fill the phyxcer register into REG_0C */
    DM9000_iow(DM9000_EPAR, DM9000_PHY | reg);

    /* Fill the written data into REG_0D & REG_0E */
    DM9000_iow(DM9000_EPDRL, (value & 0xff));
    DM9000_iow(DM9000_EPDRH, ((value >> 8) & 0xff));
    DM9000_iow(DM9000_EPCR, 0xa);    /* Issue phyxcer write command */
    udelay(500);        /* Wait write complete */
    DM9000_iow(DM9000_EPCR, 0x0);    /* Clear phyxcer write command */
    DM9000_DBG("phy_write(reg:%d, value:%d)
", reg, value);
}

static u8
DM9000_ior(int reg)
{
    u32     val;
    
    VALIDATE_ADDR_PORT(reg)

    val = *(u16*)DM9000_DATA;

    val &= 0xffff;
    
    return (u8)val;
}

static void
DM9000_iow(int reg, u8 value)
{
    VALIDATE_ADDR_PORT(reg)

    *(u16*)(DM9000_DATA) =     (u16)value;
}

#define    VALIDATE_ADDR_PORT(p) 
    if( m_uLastAddressPort != (p) ) 
        { 
            *(u16*)(DM9000_IO)  =(u16)(p);
            m_uLastAddressPort = (p);
        }

2. 网口收发

int
eth_rx(void)
{
    u8 rxbyte, *rdptr = (u8 *) NetRxPackets[0];
    int     errors=0;
    u16        RxLen;

    u32     desc;
    PDM9000_RX_DESCRIPTOR    pdesc;

    DM9000_ior(DM9000_RSR);
    DM9000_ior(DM9000_ROCR);    

    for(pdesc=(PDM9000_RX_DESCRIPTOR)&desc;;)
    {
        // probe first byte
        desc = DeviceReadDataWithoutIncrement();    
        DM9000_DBG("1:	desc is 0x%x
",desc);

        // check if packet available, 01h means available, 00h means no data
        if(pdesc->bState != 0x01)
        {
            RxLen = 0;
            break;
        }

        // get the data descriptor again
        desc = DeviceReadData();
        DM9000_DBG("2:	desc is 0x%x
",desc);        

        DM9000_DBG("len is 0x%x
",pdesc->nLength);                

        DeviceReadString(rdptr,pdesc->nLength);

        // check status, as specified in DM9000_RXSR,
        // the following bits are error
        // <3> PLE
        // <2> AE
        // <1> CE
        // <0> FOE
        if(pdesc->bStatus & MAKE_MASK4(3,2,1,0))
        {
            errors++;
            continue;
        } // of error happens

        RxLen =pdesc->nLength;
        
        break;
    } // of forever read loop

    /* Pass to upper layer */
    DM9000_DBG("passing packet to upper layer
");
    NetReceive(NetRxPackets[0], RxLen);
    return RxLen;
}

int
eth_send(volatile void *packet, int length)
{
    unsigned int loop;
#if 0
    for(loop = 0; loop<length;loop++)
    {
        printf("%02x ",*((char *)packet+loop));    
    }
    printf("
");    
#endif
    DeviceWriteString((u8*)packet,length);

    DM9000_iow(DM9000_TXPLH,HIGH_BYTE(length));
    DM9000_iow(DM9000_TXPLL,LOW_BYTE(length));
        
    // TXCR<0>, issue TX request
    DM9000_iow(DM9000_TCR, MAKE_MASK(0));

        
    DM9000_DBG("transmit done

");
    return 0;
}

数据接收时首先比对包头4个字节，第一个字节必须是0x01，第3，4字节是数据长度（减去开头的4个字节）。

接收完数据后再比对第二字节（DM9000 RSR），确认是否又错误发生。

用到的编程技巧是读取的包头4个字节直接赋值给一个u32，最低字节即为01，高两位为包长度。