Re: [PATCH] implement pm_ops.valid for everybody

Paul Mackerras
2007-03-24T03:08:36Z

Rafael J. Wysocki writes:

> > You said that if the hardware doesn't support a "turn CPU off" mode, then
> > you'd define that as being incapable of implementing suspend-to-RAM.
>
> That's _if_ the suspend-to-RAM is defined as the state in which the CPU
> is off, which I _think_ would be a reasonable definition. I don't mean the
> platforms incapable of doing this should be restricted from entering any
> system-wide low-power states, but perhaps we can call these states
> differently.

My old powerbook 3400 has a "sleep" mode where the CPU is in sleep
mode, consuming very little power (and I suspect its clock is switched
off), the RAM is kept refreshed, most of the peripherals are switched
off (except that the video chip keeps its register settings), and
wakeup is under the control of the PMU (power management unit).

My G4 powerbook has a "sleep" mode where the CPU is switched off, the
RAM is kept refreshed, most of the peripherals including the video
chip are switched off, and wakeup is under the control of the PMU.

As far as a user is concerned, both machines are doing the same thing
- they're asleep. Tell me why we should draw a distinction at a
user-visible level between what these machines are doing, when there
is no user-visible difference in behaviour?

Paul.