ACPI: Idle Processor PM Improvements
pavel at ucw.cz
Thu Sep 14 05:20:49 EDT 2006
On Tue 2006-09-12 14:18:05, Jordan Crouse wrote:
> On 12/09/06 14:14 -0400, Jim Gettys wrote:
> > > Alternatively, hack kernel to take control from X without actually
> > > switching consoles. That should be possible even with current
> > > interface.
> > This would require saving/restoring all graphics state in the kernel
> > (and X already has that state internally). Feasible, but seems like
> > duplication of effort. I haven't checked if there are any write-only
> > registers in the Geode (though, thankfully, this kind of brain damage is
> > rarer than it once was). This then begs interesting kernel/X
> > synchronization issues, of course.
> We don't need any kernel output during suspend or resume. Thus, if the VT
> doesn't change, then the kernel doesn't need worry about saving or restoring
> the graphics state, and thats the way it should be, IMHO.
> Whoever owns the current VT should be in charge of saving and restoring
> the registers.
> So, we would need some way of indicating the "ownership" of the VT. And
> in reality, we really only to know if the framebuffer console owns it or
> not, so a boolean would suffice. In the past, I've used KD_TEXT and
> KD_GRAPHICS for this purpose. As an example, on the Geode LX, I assume
> that if the vc_mode is KD_GRAPHICS, then we don't own it, and we don't
> do 2D accelerations. If the mode is KD_TEXT then we are free to use the
> 2D engine. All I needed to add ws a notifier chain to let the framebuffer
> know when the mode switched, and I was happy. I'm not sure if thats the
> smartest way to handle it permanently, but it works in a pinch.
KD_TEXT vs. KD_GRAPHICS looks like the way to go. Just tell X you want
console back, but then don't actually redraw/switch consoles. We
probably want that on normal PCs, too... console switch for
suspend-to-RAM looks ugly.
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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