Re: [PATCH 1/3] libata: avoid waking disk for several commands

[Phillip Susi <phill@thesusis.net>]

Damien Le Moal <dlemoal@kernel.org> writes:

> Yes, but only for drives that report full identify data when PUIS is enabled.
> For drives that report incomplete identify data, we have no choice but to wake
> them up. And yes, we need integration with runtime pm to set the
> initial power

Why was that again?  I think you said something about needing to set the
speed correctly so you at least need to know if this drive requires a
lower speed than the other in the PATA master/slave pair?  Wouldn't that
only require the speed information, not all identify data?

> state of the drive to standby (instead of "on") for both the ata device and its
> scsi device.

You mean if the whole device hierarchy were changed so that instead of
the scsi_host being a child of the port with the links and devices
hanging off to the side, the scsi_host would be the child of the ata device?

> I need to check that. I think there may be a better/easier way to get the
> current power state of a drive. Will get back to you on that.

That would be good.  At one point that was the way I found, and also I
think it was in the SAT-3 spec that is how REQUEST SENSE should be
implemented for ATA disks.