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    SubjectRe: AHCI power saving (was Re: Ten hours on X60s)
    Pavel Machek wrote:
    > --- a/drivers/ata/ahci.c
    > +++ b/drivers/ata/ahci.c
    > @@ -148,6 +148,8 @@ enum {
    > PORT_IRQ_PIOS_FIS | PORT_IRQ_D2H_REG_FIS,
    >
    > /* PORT_CMD bits */
    > + PORT_CMD_ALPE = (1 << 27), /* Aggressive Link Power Management Enable */
    > + PORT_CMD_ASP = (1 << 26), /* Aggressive entrance to Slumber or Partial power management states */
    > PORT_CMD_ATAPI = (1 << 24), /* Device is ATAPI */
    > PORT_CMD_LIST_ON = (1 << 15), /* cmd list DMA engine running */
    > PORT_CMD_FIS_ON = (1 << 14), /* FIS DMA engine running */
    > @@ -486,7 +488,7 @@ static void ahci_power_up(void __iomem *
    > }
    >
    > /* wake up link */
    > - writel(cmd | PORT_CMD_ICC_ACTIVE, port_mmio + PORT_CMD);
    > + writel(cmd | PORT_CMD_ICC_ACTIVE | PORT_CMD_ALPE | PORT_CMD_ASP, port_mmio + PORT_CMD);


    Therein lies a key problem. Turning on all of AHCI's aggressive power
    management features DOES save a lot of power. But at the same time, it
    shortens the life of your hard drive, particularly hard drives that are
    really PATA, but have a PATA<->SATA bridge glued on the drive to enable
    connection to SATA controllers.

    Jeff


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