I had a look to mii_send code in u-boot/cpu/mpc8xx/fec.c . It supports both FEC1 and FEC2 but anyway it seems to write always register mii-data of FEC1, look here:
/* send command to phy using mii, wait for result */ static uint mii_send(uint mii_cmd) { uint mii_reply; volatile fec_t *ep; int cnt;
ep = &(((immap_t *)CFG_IMMR)->im_cpm.cp_fec);
ep->fec_mii_data = mii_cmd; /* command to phy */
/* wait for mii complete */ cnt = 0; while (!(ep->fec_ievent & FEC_ENET_MII)) { if (++cnt > 1000) { printf("mii_send STUCK!\n"); break; } } mii_reply = ep->fec_mii_data; /* result from phy */ ep->fec_ievent = FEC_ENET_MII; /* clear MII complete */ #if 0 printf("%s[%d] %s: sent=0x%8.8x, reply=0x%8.8x\n", __FILE__,__LINE__,__FUNCTION__,mii_cmd,mii_reply); #endif return (mii_reply & 0xffff); /* data read from phy */ }