Re: [Xen-devel] S3 resume issues

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.01.13 at 19:10, Ben Guthro <ben@xxxxxxxxxx> wrote:
> On Tue, Jan 15, 2013 at 7:55 AM, Ben Guthro <ben@xxxxxxxxxx> wrote:
>> I'll continue down the rcu_check_callbacks() path, I guess.
> 
> I believe I've found the culprit of the issue, but am unsure of what
> the proper solution is.
> 
> It looks like after resume, on these newer machines, the ns16550
> registers contain all FF's - and so, the timer code was getting stuck
> in __ns16550_poll in the following stack:

Interesting. This isn't a plug in PCI device, is it? Which would
mean this is a BIOS bug (not bringing the device back online,
perhaps by keeping it disabled in some LPC register).

> A workaround seems to be to check some of the named registers at
> resume time, and bail out if they contain 0xFF's:
> ...
> This, of course means that you don't get any serial data after resume,
> which is not ideal.

Yeah, but better than not resuming. I.e. if we can really nail this
down to a platform issue, applying a workaround like what you
suggested would seem worth considering.

But I suppose this isn't helping on the laptop then? And to me this
would also imply that if you run without serial console, there
wouldn't be an issue.

Jan


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