Some problems about MDIO_timerTick() function

HI,

In the CSL what does MDIO_timerTick() used for?when I called function below

    MDIO_Device mdioDev;
    int instNum = 0;
    Uint32 mdioModeFlags = MDIO_MODEFLG_AUTONEG | MDIO_MODEFLG_FD10
                        | MDIO_MODEFLG_SPECPHYADDR;
    Uint32 mdioPhyAddr0 = 0x18;

    MDIO_open(instNum, mdioModeFlags, mdioPhyAddr0, &mdioDev);
    MDIO_initPHY( &mdioDev, mdioPhyAddr0 );

it does not change the PHY's reg, when I runned the code below

    do
    {
        printf("\n"); //without this the code will be dead .Why?
    }
    while(MDIO_EVENT_LINKUP != MDIO_timerTick(&mdioDev));

the PHY's reg will update according to the mdioModeFlags .

So what does the function MDIO_timerTick() used for?

I'm using BIOS on my device.

Thank you for reading post.