Re: [PATCH] ahci: Turn off DMA engines when there's no device attached

[Jeff Garzik <jgarzik@pobox.com>]

On 03/10/2010 03:32 PM, Matthew Garrett wrote:
> +static int ahci_is_device_present(struct ata_port *ap)
> +{
> +	void __iomem *port_mmio = ahci_port_base(ap);
> +	u8 status = readl(port_mmio + PORT_TFDATA)&  0xff;
> +
> +	/* Make sure PxTFD.STS.BSY and PxTFD.STS.DRQ are 0 */
> +	if (status&  (ATA_BUSY | ATA_DRQ))
> +		return 0;
> +
> +	/* Make sure PxSSTS.DET is 3h */
> +	status = readl(port_mmio + PORT_SCR_STAT)&  0xf;
> +	if (status != 3)
> +		return 0;
> +	return 1;


Note that this last test, reading SATA Control Register (SCR) Status, 
does not account for in-transition status, ie. devices that were just 
plugged in.

	Jeff