Lock up after resume from S3 suspend when ide dma is enabled (FC5)

[k.healy]

> There are some kernel messages showing up before it hangs,
> but they don't get written to the log because of the ide
> issues. I'm going to see if I can dump them to a usb flash
> drive.

Ok, I managed to grab some of the messages (manually, since 
everything was so locked up).

-----
...
ohci_hcd 0000:00:02.0: wakeup
ohci_hcd 0000:00:02.1: wakeup
Restarting tasks... done
ACPI: Power Button (FF) [PWRF]
ACPI: Power Button (CM) [PWRB]
hda: dma_timer_expiry: dma status == 0x21
-----

> I've tried sysrq without success, but this is probably
> because the video is locked up. Maybe sysrq over a serial
> console - is this possible with the stock Fedora kernels?
> 

I got a serial console going by adding the kernel parameter
'console=ttyS0'. Unfortunately, this doesn't survive the 
suspend, no matter whether ide dma is enabled or not, which
suggests ide dma may not be the root cause.


On that topic, I have been reading through LKML about 
nforce2 issues. About 2 years ago (kernels around 2.6.0 to 
2.6.7), there was a problem with system lockups with a lot
of the same symptoms. This was eventually traced to a 
timing issue in the nforce2 chipset connected to the "C1 
disconnect" power management features. (Search for: nforce2
apic c1halt).

As far as I know, there was no ACPI suspend support around 
at that time, so I'm wondering if this problem is being 
unmasked again by the ACPI suspend/resume code.

Ken