Re: [PATCHSET] new Power Management for libata

["zhao, forrest" <forrest.zhao@intel.com>]

On Wed, 2006-06-14 at 22:46 +0900, Tejun Heo wrote:
> Jeff Garzik wrote:
> > Tejun Heo wrote:
> >> Hello, all.
> >>
> >> This patchset implements new Power Management for libata.  Currently,
> >> only controller-wide suspend and resume are supported.  No per-device
> >> power management yet.  Both memsleep and disksleep work on supported
> >> controllers.
> > 
> > I suppose this is just an RFC?
> 
> Well, not really.
> 
> > We don't want to lose to SCSI device suspend, so merging that would be a 
> > regression AFAICS?  While we're still married to the SCSI layer, we need 
> > to do suspend through sd.c and similar paths.
> > 
> > I also wonder if any developers or users make use of the ability to 
> > suspend/resume individual pieces of hardware, as is (somewhat) supported 
> > in ata_piix in 2.6.17-rcX.
> 
> At first I thought about implementing that and asked Pavel about how to 
> discern between partial PM and system-wide PM so that libata can do 
> things bus-wide on system-wide PM event.  Pavel's response was...
> 
> "> And, one more things.  As written in the first mail, for libata, it
>  > > would be nice to know if a device suspend is due to runtime PM event
>  > > (per-device) or system wide suspend.  What do you think about this? 
>   If
>  > > you agree, what method do you recommend to determine that?
> 
> Currently, runtime pm is unsupported/broken; so any request can be
> thought as system pm.
> 								Pavel"
> 
> So, I determined to ignore per-device PM for the time being.  I think I 
> can still implement it but I'm a bit skeptical about its usefulness.  I 
> personally haven't seen any user of partial power management using sysfs 
> interface.  IIRC, dynamic power management on IDE disks from userspace 
> is done by issuing STANDBY using raw command interface.
> 
> What do you think?

Jeff and Tejun,

Have we achieved a consensus about this new PM patches? The AHCI
suspend/resume patch and ACPI-SATA patch will definitely depend on this
new PM.

Thanks,
Forrest