Re: [PATCH] implement pm_ops.valid for everybody

Matthew Locke
2007-03-23T18:18:08Z

On Mar 23, 2007, at 6:43 AM, Rafael J. Wysocki wrote:

> On Friday, 23 March 2007 00:55, David Brownell wrote:
>> On Thursday 22 March 2007 4:21 pm, Rafael J. Wysocki wrote:
>>
>>>> My answer: there is NO value to such an arbitrary restriction.
>>>
>>> I'm not talking on restrictions.
>>
>> You most certainly did talk about them.
>
> No, sorry. Apparently, I should have said more precisely what I
> meant. :-)
>
>> 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.

Again, the only reasonable platform independent defintion for STR is
that memory is powered in some way and contents preserved. The state
of the CPU and devices is platform independent. See my previous
email for an idea on how to handle it.

>
>> That's a restriction ... a very arbitrary one.
>>
>>
>>> I'm talking on being able to define
>>> _anything_ more precisely then just a low-power system-wide state.
>>
>> Me too. And I'm trying to convey to you the results of the
>> investigations I did on that topic. You don't seem to like
>> those results though ...
>>
>>
>>> And let's start from just something, please. Like STR and
>>> "standby" to begin
>>> with? At least on ACPI systems we can distinguish one from the
>>> other quite
>>> clearly, so why can't we start from that and _then_ generalize?
>>
>> That's exactly what I did. Looked also at APM, and several
>> different SOC designs (AT91, OMAP1, PXA25x, SA1100, more).
>>
>> The generalization I came up with is what I've described.
>> Namely, that coming up with one definition of those states
>> that can usefully be mapped all platforms is impractical.
>> They're just labels.
>
> Yes.
>
>> The platform implementor can choose two states to implement, but
>> non-x86 hardware states rarely match the expectations of ACPI.
>
> Yes. I which case I think the states shouldn't be _labeled_ in the
> same
> way as the "ACPI" states that they are not.
>
> My point is that _if_ we use lables like "standby", "STR", "STD",
> etc.,
> then they shouldn't mean different things on different platforms.
> So, either
> we don't use labels at all, or we should know what they mean
> regardless
> of what platform we're talking about.
>
>> So the fundamental definition needs to be in relative terms,
>> because platform-specific differences otherwise make trouble.
>
> If your point is that lables are impractical for identifying different
> low-power states of different systems, then I agree.
>
> Greetings,
> Rafael
> _______________________________________________
> linux-pm mailing list
> linux-pm@lists.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/linux-pm