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    SubjectRe: Suspend to RAM fault in VT when resuming
    Pavel Machek wrote:
    > On Tue 2007-03-13 19:42:07, Tim Gardner wrote:
    >> Pavel Machek wrote:
    >>> Hi1
    >>>> I've chased one of the 'Suspend to RAM' resume problems to a specific
    >>>> line in drivers/char/vt.c, see attached 2.6.21-rc3 diff with
    >>> Has suspend/resume ever worked on that hardware?
    >>>> TRACE_RESUME() instrumentation. The macro scr_writew resolves to '*addr
    >>>> = val', which appears to be causing the problem. I've verified that the
    >>>> pointer is not NULL, but don't know if its really valid. Its pretty
    >>>> tough to tell what is happening, but on a Dell XPS it just hangs. A Dell
    >>>> Precision blinks the keyboard lights.
    >>> It is possible that video is not initialized at that point, and that
    >>> hardware goes seriously unhappy when you access non-existing vga. Does
    >>> it resume ok when you completely disable video support?
    >> Resume works on the Dell XPS with the Ubuntu Edgy release
    >> Ubuntu-2.6.17-10.25 (2.6.17 plus a zillion fixes). Ubuntu's git tree is
    >> rsync://
    >> Ubuntu-2.6.17-8.21 is the first version where resume works, but there
    >> are a boatload of changes in ACPI and SW suspend between that and the
    >> previous tag Ubuntu-2.6.17-7.20. I don't know what made SW suspend work,
    >> but even knowing that won't tell me what broke it again.
    >> I've been avoiding the bisect process because it is quite time consuming
    >> on my slow machine, there is much branch weirdness, and I'm not that
    >> good with git. I thought if I narrowed the failure down to a small chunk
    >> of code in 2.6.21-rc3, then the answer might be obvious. No such luck, huh?
    >> This crash behaves like the video memory space has become unmapped. Is
    >> that possible?
    > That seems improbable. It is physical ram, we do not unmap that..

    The machine _has_ just come out of BIOS ACPI space. Perhaps PCI
    resources for video are hosed. All I can tell for sure is that this one
    line appears to cause some kind of crash. I'm working on finding some
    1394 resources to see if I can nail this one.

    Tim Gardner
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