On 12/20/06, Arjan van de Ven [off-list ref] wrote:

quoted

Yeah, I guess that's a problem. From a user perspective, the
functionality is only really useful if the latency is very small. I
think where possible we'd want to power down the chip while keeping the
phy up, but it would be nice to know how much power that would actually
cost us.

I'm no expert but afaik the PHY is the power hungry part, the rest is
peanuts. So if we can get the PHY to sleep most of the time that would
be great.

The MAC uses some part of power, but FYI at least e1000 already does
phy power management when IF_DOWN, if wake on lan isn't enabled, smbus
isn't enabled, etc etc.  If we started using D3 power management its
possible a whole bunch of code would go away out of e1000.

Is there some reason why we can't have the OS just do the D3
transition for all drivers that register support?  I mean, this power
management using D states is actually driver *independent* and at
least way back in the day was supposed to be implemented for "OS power
management"