Re: Re: uhci-hcd suspend/resume under the new driver model

[Pavel Machek <pavel-AlSwsSmVLrQ@public.gmane.org>]

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On Po 14-03-05 10:59:25, David Brownell wrote:
> On Monday 14 March 2005 10:44 am, Pavel Machek wrote:
> > Hi!
> > 
> > > > 	 I'll really need to make pci_choose_state
> > > > "NOP" in the current code, so that it can be safely added to the
> > > > existing drivers.
> > > 
> > > There's no point in adding NOPs.  Why bother?
> > > 
> > > Remember, the original idea behind pci_choose_state() was that
> > > PCI drivers for PM-aware devices could use that instead of their
> > > own dumb mappings between system suspend states (S0, S1, S2, S3,
> > > S4, etc) and PCI states ... which in too many cases was just to
> > > re-use the same numeric value.  That's _never_ going to be a NOP,
> > > unless Linux only ever supports PCI D3hot (ACPI D2) and S3; and
> > > likewise will never be needed for PM-stupid devices, or for those
> > > drivers with actual intelligence (e.g. Ben's video examples).
> > 
> > When I added pci_choose_state to drivers, I commented it as "no code
> > changes". I was wrong.
> 
> That's sort of what I said.  If it's a NOP, why bother?  The
> idea behind such an API was to support S1/S2/S3 suspend levels,
> where D3hot may be sub-optimal.  That's not NOP-ville.  And it
> probably ought to consult ACPI tables on some systems...

Because pm_message_t is not compatible with pci_power_t, you need
something to convert. And that something is pci_choose_state. If more
magic is needed, we'll need new function.

> > pci_choose_state() needs to return d3hot even 
> > for pmsg_freeze, because that's what old code did, and I did not audit
> > all the drivers.
> 
> Seems like a problem to me.  Do S1/S2/S3 transitions even
> need a "freeze" transition?  I thought we'd agreed they don't;

That's not the problem.

Old code put devices into D3hot in swsusp "freeze" case. We'll need to
do the same now, slowly auditing the drivers and removing that
unneccessary D0->D3hot->D0 transition.

								Pavel
-- 
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