[ltp] High power consumption after suspend/resume cycle

[Robert Tomsick]

On Wed, 2009-10-07 at 10:50 -0400, Theodore Tso wrote:
> On Wed, Oct 07, 2009 at 12:37:02PM +0100, Robert Tomsick wrote:
> > 
> > 2) Build a custom kernel and apply the patch to power off unused
> SATA
> > ports.
> > 
> 
> Which patch are you using to do this?  Can you send a pointer to it?
> What kernel version are you using?  With modern kernels I thought all
> that was necessary was:
> 
> for i in /sys/class/scsi_host/*/link_power_management_policy; do
>     echo min_power > $i
> done
> 
> Do you have a patch that does better?

I do indeed.

The line you posted will enable power-saving for all ports, but AFAIK it
won't actually shut them off.

I found a patch (submitted to LKML IIRC) that actually disables all
unused ports at init. time.  In theory it saves 0.75W -- YMMV though.

The LKML thread is here:

http://lkml.org/lkml/2008/5/8/469

I think that's where I got the version I added to my personal patchset.
It looks about the same.

I've got local copies that apply cleanly to the Debian Lenny kernel
sources and the Ubuntu 9.04 kernel sources.  I can throw them up here if
anyone is interested.

-- Rob