Re: [linux-pm] [patch/rft 2.6.17-rc2] swsusp resume must not device_suspend()

["Rafael J. Wysocki" <rjw@sisk.pl>]

Hi,

On Monday 24 April 2006 23:29, David Brownell wrote:
> I've noticed a bunch of problem reports that go like this:
> 
>  - boot system with some USB devices attached
>  - echo disk > /sys/power/state
>  - ... later resume ...
>  - now those USB devices don't work right
>  - unplug them/replug them, all is OK
> 
> I recently observed this myself and tracked down one problem.  The solution
> involves what kexec() does in much the same situation:  before starting a
> new kernel, most hardware needs to be reset.  Today, swsusp will suspend it
> instead, which is the root cause of the problem.
> 
> This seems like something that might need to sit in the MM tree for
> a while, as it's a longstanding bug and the fix could shake loose driver
> goofs.  Luckily there's a partial workaround already in wide use:  link
> drivers as modules if they use true suspend states (like all USB HCDs),
> don't link them statically into the kernel image.
> 
> That workaround is partial because when BIOS takes over a controller, the
> resume() method has to handle that nasty case too!  Last I checked, all
> the USB HCDs do handle that case; and few drivers other than those HCDs
> would ever need to worry about such issues.

I agree with this change but I think it'll cause some strange things to happen
for some time.

Greetings,
Rafael


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