pxa27x_spi.c

intel 32位CPUpxa27x的spi通信程序

/*> From: Stephen Street <[e-mail]>
> 
> The driver turns a PXA2xx synchronous serial port (SSP) into a SPI master 
> controller (see Documentation/spi/spi_summary). The driver has the following
> features:

I've not tested this on my PXA27x platform yet (I'll try and get this
done this tomorrow) but a few comments.

> --- linux-2.6.16-rc2/drivers/spi/pxa2xx_spi.c	1969-12-31 16:00:00.000000000 -0800
> +++ linux-spi/drivers/spi/pxa2xx_spi.c	2006-02-06 18:39:45.339334630 -0800
*/

#define CLOCK_SPEED_HZ 3686400

//PXA27x has a clock speed of 13000000 Hz.
> +	chip->cr0 = SSCR0_SerClkDiv((CLOCK_SPEED_HZ / spi->max_speed_hz) + 2)

Consider spi->max_speed_hz == CLOCK_SPEED_HZ which gives a divisor of 3
(when it should be 1).

You need SSCR0_SerClkDiv(CLOCK_SPEED_HZ / (spi->max_speed_hz + 1) + 1)
for the correct divisor and for proper rounding.

/* Attach to IRQ */
	irq = platform_get_irq(pdev, 0);
	if (irq == 0) {
		dev_err(&pdev->dev, "irq resource not defined\n");
		status = -ENODEV;
		goto out_error_master_alloc;
	}

Greg K-H has a patch pending that makes platform_get_irq() return -ENXIO
instead of 0 on error.  This is required for SSP3 on the PXA27x which
uses IRQ 0.

> +	/* Release IRQ */
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq != 0)
> +		free_irq(irq, drv_data);

Similarly.

David Vrabel
-- 
David Vrabel, Design Engineer

Arcom, Clifton Road           Tel: [phone] ext. 3233
Cambridge CB1 7EA, UK         Web: http://www.arcom.com/
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