Re: [PATCH 2/2] Fix console handling during suspend/resume

Randy.Dunlap
2006-06-14T00:06:09Z

On Wed, 14 Jun 2006 10:00:08 +1000 Nigel Cunningham wrote:

> Hi.
>
> On Wednesday 14 June 2006 09:46, Linus Torvalds wrote:
> > On Tue, 13 Jun 2006, David Brownell wrote:
> > > Here's a related patch (well, "hack") I found helpful ... specifically to
> > > help let _serial_ consoles be more useful.
> >
> > I just checked.
> >
> > I think exactly _two_ of the six machines I have around my desk have
> > serial ports, and of those two, one is permanently turned off because it's
> > old, noisy, and just not interesting.
> >
> > Maybe I'm more progressive than most, but I personally consider serial
> > lines pretty much dead.
>
> Usb to serial converters are not completely unheard of, though. My old
> omnibook even came with one. It's the one bit I still use :)

and usb serial-console works, although not during early init (it has
to wait for the usb subsystem to be ready).

> > > Although I must say I like Nigel's "BDI-2000 per developer" hack better.
> > > Even though not all boxes can hook up to a JTAG module. :(
> >
> > Umm. Even more importantly, I don't think the JTAG interfaces for PC's are
> > necessarily even available. There is read-out logic for ARM's and embedded
> > PPC, but have you ever seen anything for something non-embedded?
>
> Yeah. Sort of kills that idea, doesn't it?
>
> > A really useful trick the PPC people use was to put the firewire
> > controller into "anybody can read" mode, and use it as a kernel debugger
> > when it basically becomes a remote memory DMA engine. I used that to debug
> > some kernel hangs, and it was very nice.
> >
> > However, that won't survive a power event, so it might be useful to debug
> > suspend problems, but generally not resume problems.
>
> Since just about every problem occurs at resume time, it really does seem to
> me to be the case that we have to use the rtc. Great idea, by the way.

---
~Randy