Re: [patch] suspend: update warnings

[Nigel Cunningham <ncunningham@cyclades.com>]

Hi.

On Tue, 2005-08-23 at 22:50, Pavel Machek wrote:
> Hi!
> 
> > > + * If you have unsupported (*) devices using DMA, you may have some
> > > + * problems. If your disk driver does not support suspend... (IDE does),
> > > + * it may cause some problems, too. If you change kernel command line 
> > > + * between suspend and resume, it may do something wrong. If you change 
> > > + * your hardware while system is suspended... well, it was not good idea;
> > > + * but it wil probably only crash.
> > 
> > The most common driver issues I see involve:
> > - USB being built in or as modules that are still loaded while
> > suspending (getting better, but not there yet)
> > - DRI being used in X where the drivers don't properly support
> > suspend/resume (NVidia esp)
> > - Firewire
> > - CPU Freq  (improving too)
> > 
> > It might be good to mention these areas too.
> 
> Well, right; but those 'only' cause system to crash during suspend. I
> was talking about really dangerous stuff.
> 
> Both usb and cpufreq seems to work okay here.

It depends on what you're using. I believe one of the usb root hub
drivers is okay, the others aren't. Similar for cpufreq. USB certainly
accounts for a high percentage of the failures I see.

> I've added FAQ entry at the end:
> 
> Q: What information is usefull for debugging suspend-to-disk problems?
> 
> A: Well, last messages on the screen are always useful. If something
> is broken, it is usually some kernel driver, therefore trying with as
> little as possible modules loaded helps a lot. I also prefer people to
> suspend from console, preferably without X running. Booting with
> init=/bin/bash, then swapon and starting suspend sequence manually
> usually does the trick. Then it is good idea to try with latest
> vanilla kernel.
> 
> "Known problematic" modules are; be sure to unload them before
> suspend:
> - DRI being used in X where the drivers don't properly support
> suspend/resume (NVidia esp)
> - Firewire
> - SCSI
> 
> 
> > Perhaps the 'changing your hardware' could mention that replacing faulty
> > hardware may be safe.
> 
> I do not want to encourage people to do that. Yep, its probably safe,
> no, I do not want them to know.

:>

Thanks

Nigel
-- 
Evolution.
Enumerate the requirements.
Consider the interdependencies.
Calculate the probabilities.

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