SPI_MAX_XFER
host->max_dma_len = SPI_MAX_XFER;
SPI_MAX_XFER, &rx_nents) / qup->w_size;
SPI_MAX_XFER, &tx_nents) / qup->w_size;
iterations = n_words / SPI_MAX_XFER; /* round down */
qup->n_words = SPI_MAX_XFER;
qup->n_words = n_words % SPI_MAX_XFER;
qup->tx_buf = xfer->tx_buf + offset * SPI_MAX_XFER;
qup->rx_buf = xfer->rx_buf + offset * SPI_MAX_XFER;
timeout = DIV_ROUND_UP(min_t(unsigned long, SPI_MAX_XFER,