Any feedback on this?
On Wed, Mar 10, 2010 at 03:32:30PM -0500, Matthew Garrett wrote:
> According to section 10.3.1 of the AHCI spec, PxCMD.ST must not be set
> unless there's a device attached. Following this saves us a measurable
> quantity of power and does not impair hotplug support. Based on a patch
> by Kristen Carlson Accardi.
>
> Signed-off-by: Matthew Garrett <mjg@xxxxxxxxxx>
> Cc: Kristen Carlson Accardi <kristen.c.accardi@xxxxxxxxx>
> ---
> drivers/ata/ahci.c | 19 +++++++++++++++++++
> 1 files changed, 19 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> index 6bd930b..ff08317 100644
> --- a/drivers/ata/ahci.c
> +++ b/drivers/ata/ahci.c
> @@ -1016,11 +1016,30 @@ static int ahci_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val)
> return -EINVAL;
> }
>
> +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;
> +}
> +
> static void ahci_start_engine(struct ata_port *ap)
> {
> void __iomem *port_mmio = ahci_port_base(ap);
> u32 tmp;
>
> + if (!ahci_is_device_present(ap))
> + return;
> +
> /* start DMA */
> tmp = readl(port_mmio + PORT_CMD);
> tmp |= PORT_CMD_START;
> --
> 1.6.6.1
>
> --
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--
Matthew Garrett | mjg59@xxxxxxxxxxxxx
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