Re: 2.6.25-rc2 System no longer powers off after suspend-to-disk. Screen becomes green.

Linus Torvalds
2008-02-20T18:37:04Z

On Thu, 21 Feb 2008, Jeff Chua wrote:
>
> > That said, before you do anything else, try if suspend-to-RAM works.
>
> Linus, guess I missed this part ... so before touch anything, I did
> tried suspend-to-ram, and it works on console and in X.

Ok, so this is with clean current -git, and nothing disabled?

> And suspend-to-disk hangs, but I can still press and hold the power
> button to power it off.

The "press and hold for five seconds" is actually a hardware feature of
the southbridge (well, I guess there is "software" in there too, but it's
the embedded kind). So the fact that it powers off at that point means
nothing, it just means that ok, your kernel is hung, but the hardware
still works ;)

This *sounds* like some part of the suspend-to-disk sequence is doing
something stupid like trying to access the screen after it has been turned
off, which doesn't surprise me at all. My oft-stated opinion has been that
suspend-to-disk isn't a suspend at all, and should never have been
confused with "suspending" anything.

It's "snapshot-and-restore", and my opinion is that:

- it should *never* call "suspend()"/"resume()" at all (that should be
reserved purely for suspend-to-RAM and has real power management
issues!)

- it should have a totally separate "halt/unhalt/restore" thing
that has nothing what-so-ever to do with power management, and is
purely about stopping the hardware for things like USB and network
cards (which otherwise do things like scan their command lists
asynchronously) and making sure that the driver state is consistent
with that stopped hw state.

- the people who confuse snapshot/restore with suspend/resume are
horrible people that cause problems exactly because driver people then
get those things mixed up, and something like the video suspend/resume
should probably never have impacted suspend-to-disk in the first place!

HOWEVER, that's a separate fight I've had, and in the meantime:

> Then upon powering on and resume, I get the ugly green "console" screen.
> I can still type and move around. Starting X runs fine. Ctrl-Alt-Del or
> switching back to console will get back to the green screen.

.. so this implies that while the laptop apparently hung at the end of the
snapshotting, the snapshotting did actually work, and it must have hung at
the very end, presumably when it tried to actually turn the power off.

So there seems to be two (probably largely independent) problems:

- the hang at shutdown that requires you to press-and-hold the power
button to actually cut power.

At a guess: putting the VGA device into D3hot makes the ACPI code that
actually does the shutoff unhappy. Probably because it wants to access
the device, and ends up not ever getting the replies it wants, since
the hardware has been turned off.

- the fact that we restore something wrong for you and the screen is
green.

At a guess: the restore_vga ends up restoring some state that wasn't
correctly and fully saved.

IOW, I think your patch that disables the two lines actually ends up
pretty much matching the two *different* problems. Can you confirm that
doing those two parts of that patch individually actually does
individually fix the two issues? (Ie disabling D3hot makes it shut down
nicely but resume with green text, while disabling just restore_vga() ends
up with shutdown problems, but once you press-and-hold the power button,
the thing will then restore nicely)+

Linus

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