linux-kernel - Re: [PATCH v4] spi: add OpenCores tiny SPI driver

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Date:	Thu, 03 Feb 2011 07:20:32 -0800
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	Thomas Chou <thomas@...ron.com.tw>
CC:	David Brownell <dbrownell@...rs.sourceforge.net>,
	Grant Likely <grant.likely@...retlab.ca>,
	nios2-dev@...c.et.ntust.edu.tw,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	spi-devel-general@...ts.sourceforge.net
Subject: Re: [PATCH v4] spi: add OpenCores tiny SPI driver

On 02/03/2011 02:37 AM, Thomas Chou wrote:
> This patch adds support of OpenCores tiny SPI driver.
>
> http://opencores.org/project,tiny_spi
>

> +static int tiny_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
> +{
> +	struct tiny_spi *hw = tiny_spi_to_hw(spi);
> +	const u8 *txp = t->tx_buf;
> +	u8 *rxp = t->rx_buf;
> +	unsigned int i;
> +
> +	if (hw->irq>= 0) {
> +		/* use intrrupt driven data transfer */
> +		hw->len = t->len;
> +		hw->txp = t->tx_buf;
> +		hw->rxp = t->rx_buf;
> +		hw->txc = 0;
> +		hw->rxc = 0;
> +
> +		/* send the first byte */
> +		if (t->len>  1) {
> +			writeb(hw->txp ? *hw->txp++ : 0,
> +			       hw->base + TINY_SPI_TXDATA);
> +			hw->txc++;
> +			writeb(hw->txp ? *hw->txp++ : 0,
> +			       hw->base + TINY_SPI_TXDATA);
> +			hw->txc++;
> +			writeb(TINY_SPI_STATUS_TXR, hw->base + TINY_SPI_STATUS);
> +		} else {
> +			writeb(hw->txp ? *hw->txp++ : 0,
> +			       hw->base + TINY_SPI_TXDATA);
> +			hw->txc++;
> +			writeb(TINY_SPI_STATUS_TXE, hw->base + TINY_SPI_STATUS);
> +		}
> +
> +		wait_for_completion(&hw->done);
> +	} else if (txp&&  rxp) {
> +		/* we need to tighten the transfer loop */
> +		writeb(*txp++, hw->base + TINY_SPI_TXDATA);
> +		if (t->len>  1) {
> +			writeb(*txp++, hw->base + TINY_SPI_TXDATA);
> +			for (i = 2; i<  t->len; i++) {
> +				u8 rx, tx = *txp++;
> +				while (!(readb(hw->base + TINY_SPI_STATUS)&
> +					 TINY_SPI_STATUS_TXR))
> +					cpu_relax();

Putting the read status, cpu releax in an inline function would make this 
function a lot easier to read.

> +				rx = readb(hw->base + TINY_SPI_TXDATA);
> +				writeb(tx, hw->base + TINY_SPI_TXDATA);
> +				*rxp++ = rx;
> +			}
> +			while (!(readb(hw->base + TINY_SPI_STATUS)&
> +				 TINY_SPI_STATUS_TXR))
> +				cpu_relax();
> +			*rxp++ = readb(hw->base + TINY_SPI_TXDATA);
> +		}
> +		while (!(readb(hw->base + TINY_SPI_STATUS)&
> +			 TINY_SPI_STATUS_TXE))
> +			cpu_relax();
> +		*rxp++ = readb(hw->base + TINY_SPI_RXDATA);
> +	} else if (rxp) {
> +		writeb(0, hw->base + TINY_SPI_TXDATA);
> +		if (t->len>  1) {
> +			writeb(0,
> +			       hw->base + TINY_SPI_TXDATA);
> +			for (i = 2; i<  t->len; i++) {
> +				u8 rx;
> +				while (!(readb(hw->base + TINY_SPI_STATUS)&
> +					 TINY_SPI_STATUS_TXR))
> +					cpu_relax();
> +				rx = readb(hw->base + TINY_SPI_TXDATA);
> +				writeb(0,
> +				       hw->base + TINY_SPI_TXDATA);
> +				*rxp++ = rx;
> +			}
> +			while (!(readb(hw->base + TINY_SPI_STATUS)&
> +				 TINY_SPI_STATUS_TXR))
> +				cpu_relax();
> +			*rxp++ = readb(hw->base + TINY_SPI_TXDATA);
> +		}
> +		while (!(readb(hw->base + TINY_SPI_STATUS)&
> +			 TINY_SPI_STATUS_TXE))
> +			cpu_relax();
> +		*rxp++ = readb(hw->base + TINY_SPI_RXDATA);
> +	} else if (txp) {
> +		writeb(*txp++, hw->base + TINY_SPI_TXDATA);
> +		if (t->len>  1) {
> +			writeb(*txp++, hw->base + TINY_SPI_TXDATA);
> +			for (i = 2; i<  t->len; i++) {
> +				u8 tx = *txp++;
> +				while (!(readb(hw->base + TINY_SPI_STATUS)&
> +					 TINY_SPI_STATUS_TXR))
> +					cpu_relax();
> +				writeb(tx, hw->base + TINY_SPI_TXDATA);
> +			}
> +		}
> +		while (!(readb(hw->base + TINY_SPI_STATUS)&
> +			 TINY_SPI_STATUS_TXE))
> +			cpu_relax();
> +	} else {
> +		writeb(0, hw->base + TINY_SPI_TXDATA);
> +		if (t->len>  1) {
> +			writeb(0,
> +			       hw->base + TINY_SPI_TXDATA);
> +			for (i = 2; i<  t->len; i++) {
> +				while (!(readb(hw->base + TINY_SPI_STATUS)&
> +					 TINY_SPI_STATUS_TXR))
> +					cpu_relax();
> +				writeb(0,
> +				       hw->base + TINY_SPI_TXDATA);
> +			}
> +		}
> +		while (!(readb(hw->base + TINY_SPI_STATUS)&
> +			 TINY_SPI_STATUS_TXE))
> +			cpu_relax();
> +	}
> +	return t->len;
> +}
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