linux-kernel - Re: [Suspend-devel] 2.6.25-rc2 System no longer powers off aftersuspend-to-disk. Screen becomes green.

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Date:	Thu, 21 Feb 2008 17:35:38 -0800
From:	Jesse Barnes <jesse.barnes@...el.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Jeff Chua <jeff.chua.linux@...il.com>,
	Romano Giannetti <romano@....icai.upcomillas.es>,
	suspend-devel List <suspend-devel@...ts.sourceforge.net>,
	Dave Airlie <airlied@...ux.ie>, Greg KH <gregkh@...e.de>,
	lkml <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-acpi@...r.kernel.org
Subject: Re: [Suspend-devel] 2.6.25-rc2 System no longer powers off aftersuspend-to-disk. Screen becomes green.

On Thursday, February 21, 2008 5:28 pm Linus Torvalds wrote:
> On Thu, 21 Feb 2008, Jesse Barnes wrote:
> > So the advantage of the kernel suspend/resume hooks for the DRM layer is
> > that the kernel video drivers can do full state save/restore (which X
> > usually doesn't do, and isn't really designed to do), so that if your
> > platform *doesn't* do it all, you'll still end up with a usable machine
> > in the end.
>
> Well, I'm also hoping that eventually we could even just not do the VT
> switch at all, and the kernel can treat X as "just another user process"
> that it freezes.

Hell yes.

> At least from a mode setting standpoint.
>
> We'd still want to make sure that X repaints the screen if the contents
> were lost, of course. And this is going to depend very intimately on the
> type of graphics card and whether the video RAM is saved by STR or not -
> for the Intel integrated graphics kind of situation, the video RAM will be
> refreshed along with all the other memory, but for other cards we may end
> up having to do the VT switch not so much for modesetting reasons as just
> a way to get X to save and restore all the *other* state.

Drivers supporting kernel modesetting will have to stuff their VRAM somewhere, 
yeah.  Hopefully X won't have much to do with it though...

> How close is the i915 driver from not having to even signal X? Or is that
> just a pipedream of mine?

It's there in the modesetting tree (though the requisite changes to avoid VT 
notification aren't done, it should all work fine).

Jesse
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