/* Configure Port B ethernet pin (PB11) */
GPIOB->MODER &= ~(0x3<<22);
GPIOB->MODER |= (0x2<<22); /* Pins to alternate function */
GPIOB->OTYPER &= ~(1<<11); /* Pin in push-pull mode */
GPIOB->OSPEEDR |= (0x3<<22); /* Slew rate as 100MHz pin */
GPIOB->PUPDR &= ~(0x3<<22); /* No pull up, no pull down */

GPIOB->AFR[1] &= ~(0xf<<12);
GPIOB->AFR[1] |= (0xb<<12); /* Pin to AF11 (Ethernet) */

if (((id1 << 16) | (id2 & 0xFFF0)) == PHY_ID_ST802RT1) {

...

}

regv = read_PHY (PHY_REG_XSTAT); // такого регистра в KS8721 не найдено
if (regv & (1 << 8)) {
/* Full-duplex connection */
conn |= PHY_CON_SET_FULLD;
}
if (regv & (1 << 9)) {
/* 100Mb/s mode */
conn |= PHY_CON_SET_100M;
}