REG_SLAVE_SELECT
reg = mpfs_spi_read(mspi, REG_SLAVE_SELECT);
mpfs_spi_write(mspi, REG_SLAVE_SELECT, reg);
reg = mpfs_spi_read(mspi, REG_SLAVE_SELECT);
mpfs_spi_write(mspi, REG_SLAVE_SELECT, reg);
mpfs_spi_write(spi, REG_SLAVE_SELECT, spi->pending_slave_select);
mpfs_spi_write(spi, REG_SLAVE_SELECT, spi->pending_slave_select);