PCH_SPBRR
pch_spi_setclr_reg(host, PCH_SPBRR, n_spbr, MASK_SPBRR_SPBR_BITS);
pch_spi_setclr_reg(host, PCH_SPBRR, 0, SPBRR_SIZE_BIT);
pch_spi_setclr_reg(host, PCH_SPBRR, SPBRR_SIZE_BIT, 0);
__func__, pch_spi_readreg(spi->controller, PCH_SPBRR),