VIAI2C_REG_MCR
writew(MCR_APB_166M, i2c->base + VIAI2C_REG_MCR);
iowrite16(priv->mcr, i2c->base + VIAI2C_REG_MCR);
priv->mcr = ioread16(i2c->base + VIAI2C_REG_MCR);