static int sh_msiof_transfer_one()

in spi-sh-msiof.c [907:1048]

• 115 lines of code
• 30 McCabe index (conditional complexity)

static int sh_msiof_transfer_one(struct spi_controller *ctlr,
				 struct spi_device *spi,
				 struct spi_transfer *t)
{
	struct sh_msiof_spi_priv *p = spi_controller_get_devdata(ctlr);
	void (*copy32)(u32 *, const u32 *, unsigned int);
	void (*tx_fifo)(struct sh_msiof_spi_priv *, const void *, int, int);
	void (*rx_fifo)(struct sh_msiof_spi_priv *, void *, int, int);
	const void *tx_buf = t->tx_buf;
	void *rx_buf = t->rx_buf;
	unsigned int len = t->len;
	unsigned int bits = t->bits_per_word;
	unsigned int bytes_per_word;
	unsigned int words;
	int n;
	bool swab;
	int ret;

	/* reset registers */
	sh_msiof_spi_reset_regs(p);

	/* setup clocks (clock already enabled in chipselect()) */
	if (!spi_controller_is_slave(p->ctlr))
		sh_msiof_spi_set_clk_regs(p, t);

	while (ctlr->dma_tx && len > 15) {
		/*
		 *  DMA supports 32-bit words only, hence pack 8-bit and 16-bit
		 *  words, with byte resp. word swapping.
		 */
		unsigned int l = 0;

		if (tx_buf)
			l = min(round_down(len, 4), p->tx_fifo_size * 4);
		if (rx_buf)
			l = min(round_down(len, 4), p->rx_fifo_size * 4);

		if (bits <= 8) {
			copy32 = copy_bswap32;
		} else if (bits <= 16) {
			copy32 = copy_wswap32;
		} else {
			copy32 = copy_plain32;
		}

		if (tx_buf)
			copy32(p->tx_dma_page, tx_buf, l / 4);

		ret = sh_msiof_dma_once(p, tx_buf, rx_buf, l);
		if (ret == -EAGAIN) {
			dev_warn_once(&p->pdev->dev,
				"DMA not available, falling back to PIO\n");
			break;
		}
		if (ret)
			return ret;

		if (rx_buf) {
			copy32(rx_buf, p->rx_dma_page, l / 4);
			rx_buf += l;
		}
		if (tx_buf)
			tx_buf += l;

		len -= l;
		if (!len)
			return 0;
	}

	if (bits <= 8 && len > 15) {
		bits = 32;
		swab = true;
	} else {
		swab = false;
	}

	/* setup bytes per word and fifo read/write functions */
	if (bits <= 8) {
		bytes_per_word = 1;
		tx_fifo = sh_msiof_spi_write_fifo_8;
		rx_fifo = sh_msiof_spi_read_fifo_8;
	} else if (bits <= 16) {
		bytes_per_word = 2;
		if ((unsigned long)tx_buf & 0x01)
			tx_fifo = sh_msiof_spi_write_fifo_16u;
		else
			tx_fifo = sh_msiof_spi_write_fifo_16;

		if ((unsigned long)rx_buf & 0x01)
			rx_fifo = sh_msiof_spi_read_fifo_16u;
		else
			rx_fifo = sh_msiof_spi_read_fifo_16;
	} else if (swab) {
		bytes_per_word = 4;
		if ((unsigned long)tx_buf & 0x03)
			tx_fifo = sh_msiof_spi_write_fifo_s32u;
		else
			tx_fifo = sh_msiof_spi_write_fifo_s32;

		if ((unsigned long)rx_buf & 0x03)
			rx_fifo = sh_msiof_spi_read_fifo_s32u;
		else
			rx_fifo = sh_msiof_spi_read_fifo_s32;
	} else {
		bytes_per_word = 4;
		if ((unsigned long)tx_buf & 0x03)
			tx_fifo = sh_msiof_spi_write_fifo_32u;
		else
			tx_fifo = sh_msiof_spi_write_fifo_32;

		if ((unsigned long)rx_buf & 0x03)
			rx_fifo = sh_msiof_spi_read_fifo_32u;
		else
			rx_fifo = sh_msiof_spi_read_fifo_32;
	}

	/* transfer in fifo sized chunks */
	words = len / bytes_per_word;

	while (words > 0) {
		n = sh_msiof_spi_txrx_once(p, tx_fifo, rx_fifo, tx_buf, rx_buf,
					   words, bits);
		if (n < 0)
			return n;

		if (tx_buf)
			tx_buf += n * bytes_per_word;
		if (rx_buf)
			rx_buf += n * bytes_per_word;
		words -= n;

		if (words == 0 && (len % bytes_per_word)) {
			words = len % bytes_per_word;
			bits = t->bits_per_word;
			bytes_per_word = 1;
			tx_fifo = sh_msiof_spi_write_fifo_8;
			rx_fifo = sh_msiof_spi_read_fifo_8;
		}
	}

	return 0;
}